Why contagious yawning does not (yet) equate to empathy

HIGHLIGHTSContagious yawning has been linked with empathy.Evidence supporting this connection is inconsistent and inconclusive.More controlled studies are needed to explicitly test this association.  Various studies and researchers have proposed a link between contagious yawning and empathy, yet the conceptual basis for the proposed connection is not clear and deserves critical evaluation. Therefore, we systematically examined the available empirical evidence addressing this association; i.e., a critical review of studies on inter‐individual differences in contagion and self‐reported values of empathy, differences in contagion based on familiarity or sex, and differences in contagion among individuals with psychological disorders, as well as developmental research, and brain imaging and neurophysiological studies. In doing so, we reveal a pattern of inconsistent and inconclusive evidence regarding the connection between contagious yawning and empathy. Furthermore, we identify study limitations and confounding variables, such as visual attention and social inhibition. Future research examining links between contagious yawning and empathy requires more rigorous investigation involving objective measurements to explicitly test for this connection.

Related papers:

title: Yawning as a stereotyped action pattern and releasing stimulus.
abstract: Yawning was induced by instructing subjects to “think about yawning.” Yawns were consistent in duration (X = 5.9 s), periodic (X interyawn interval = 68.3 s), and within-subject stability in yawn duration and frequency was maintained for at least several weeks. These and other characteristics qualified yawning as a stereotyped action pattern. Although visually observed yawns were potent yawn releasing stimuli, “thinking about” or reading about yawning also elicited yawning and were additional vectors for its “infectiousness.” The respiratory, stretching and “imitative” aspects of yawning were also evaluated.

title: Curious behavior: Yawning, laughing, hiccupping, and beyond.
abstract: A review of the book "Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond," by Robert R. Provine is presented.

title: Is yawning an arousal defense reflex?
abstract: Despite the fact that yawning is a reality of everyday life, its study is not included in the curriculum of medical schools, and most medical textbooks barely mention its existence. Two factors may help to explain this puzzling situation: (a) yawning's borderline position between psychology and neurology, and (b) researchers' lack of understanding as to why people yawn. After review of the literature and personal observation, it is concluded that yawning is a complex arousal defense reflex located in the reticular brainstem with a peripheral and central arche, whose aim is to reverse brain hypoxia. Yawning occurs with loss of interest (boredom) and may or may not be associated with fatigue. By reversing drowsiness, yawning avoids a decreased concentration capacity resulting from borderline hypoxia. It is hoped that this article will stimulate further research on the phenomenon.

title: SOME ANTECEDENTS AND CONSEQUENCES OF YAWNING
abstract: Attempts were made in three experiments to induce human subjects to yawn reliably in the laboratory. In subjects who believed they were not observed, reading about yawning did increase their frequency of yawning, compared to reading about scratching or day dreaming. In the second experiment, performing a spontaneous yawn decreased skin conductance, but "faked" yawns did not have this effect. In subjects under observation during the third experiment neither boredom, vigilance, nor reading about yawning induced the act.

title: Yawn duration predicts brain weight and cortical neuron number in mammals
abstract: Research indicates that the motor action pattern of yawning functions to promote cortical arousal and state change through enhanced intracranial circulation and brain cooling. Because the magnitude of this response likely corresponds to the degree of neurophysiological change, we hypothesized that interspecies variation in yawn duration would correlate with underlying neurological differences. Using openly accessible data, we show that both the mean and variance in yawn duration are robust predictors of mammalian brain weight and cortical neuron number (ρ-values > 0.9). Consistent with these effects, primates tend to have longer and more variable yawn durations compared with other mammals. Although yawning has long been considered a stereotyped action pattern, these findings reveal substantial variation in this response and highlight the importance of measuring yawn duration in future research.

title: Field observations of yawning and activity in humans
abstract: Rates of wrist activity and yawning were recorded continuously for 7-15 days in adult human male and female subjects. In the 15 min following 747 yawns wrist motion increased reliably in all subject records. The data were consistent with an hypothesis that yawning is predictive of an increase in activity level. In a second study, data from daily logs kept by 45 subjects confirmed previous findings that yawning frequency is unrelated to prior amount of sleep, or to times of awaking or retiring. More yawning occurred during the week than during weekends.

title: Yawning: Relation to Sleeping and Stretching in Humans
abstract: The temporal relations among yawning, sleeping, and stretching were investigated by having undergraduate college students record the occurrences of these behaviors during a one-week period. Yawning was most frequent during the hour before sleeping and after waking. In contrast, stretching was common only during the hour after waking. Concurrent yawning and stretching were common but stretching was accompanied more often by yawning than vice-versa. The temporal proximity of yawning to sleep and waking times is probably the basis for yawning as a paralinguistic signal for drowsiness. The role of contagious yawning in synchronizing the behavior and physiological state of a group is considered.

title: Yawning in morning and evening types
abstract: Yawning occurs more frequently in the early morning and in the late evening, close to sleep onset and after the awakening, and it might be linked to sleep propensity. We aimed to study yawning and its temporal distribution in morning and evening subjects who display different sleep-wake and sleepiness rhythms. Sixteen healthy young adults (8 evening-types and 8 morning-types, matched for age and gender) have been selected and instructed to keep their habitual sleep schedules and to signal every yawning occurrence for three consecutive days. Results show that evening-types yawn more frequently than morning-types, particularly during morning hours. Yawning frequency decreases across daytime in evening-types reaching its lowest level in the early evening and increases thereafter. Instead, in morning-types, yawning frequency remains quite low during daytime and increases in the evening. Moreover, both morning and evening types show a progressive increase of yawning frequency in the hours preceding sleep onset, whereas they differ after the awakening. Evening-types show a higher yawning frequency that remains quite stable in the hours following the awakening, while morning-types display a decline in yawning frequency. Our findings show that the temporal distribution of yawning frequency differs between chronotypes, supporting the hypothesis that differences in sleep-wake rhythm affect yawning, which could represent a behavioural sign of sleep propensity.

title: Yawning and thermoregulation in budgerigars, Melopsittacus undulatus

abstract: Yawning is a widespread behavioural response expressed in all classes of vertebrates. There is, however, little agreement on its biological significance. One current hypothesis states that yawning serves as a thermoregulatory mechanism that occurs in response to increases in brain and/or body temperature. The brain-cooling hypothesis further stipulates that, as ambient temperature increases and approaches (but does not exceed) body temperature, yawning should increase as a consequence. We tested this hypothesis in a sample of 20 budgerigars, Melopsittacus undulatus, through the manipulation of room temperature. Birds were exposed to three separate conditions (control temperature (22 °C), increasing temperature (22–34 °C), and high temperature (34–38 °C)) in a repeated measures design, with each condition lasting 21 min. The incidence of yawning differed significantly across conditions (4.20 ± 2.39 yawns per bird in the increasing temperature condition, compared to 2.05 ± 1.90 and 1.25 ± 0.72 yawns per bird, in the high temperature and control conditions, respectively). These findings are consistent with the hypothesis that yawning serves a thermoregulatory function.

title: Zum Problem des Gähnens bei Reptilien
abstract: Yawning in reptiles was investigated in field observations of various lizard and tortoise species and in laboratory experiments with the tortoises Testudo h. hermanni and Emys orbicularis. In the experiments the animals' reactions to various conditions of temperature, air O2 and CO2 content, fatigue and hunger, were tested. Yawning and related or similar motor patterns are described and discussed.

title: The emergence of fetal behaviour. I. Qualitative aspects.
abstract: The emergence of spontaneous fetal motility during the first 20 weeks of gestation was studied longitudinally in 11 healthy nulliparae, using real-time ultrasound. The aim of this investigation was to study the onset and developmental course of spontaneously generated specific fetal movement patterns. 60-min observations were repeated weekly from 7 to 15 weeks and at 16/17 and 18/19 weeks. The qualitative aspects of fetal motility and posture were analyzed during video recording. Sixteen distinct movement patterns (just discernible movements; startle; general movements; hiccup; breathing; isolated arm or leg movements; isolated retroflexion/rotation and anteflexion of the head; jaw movements; sucking and swallowing; hand-facecontact; stretch; yawn; rotation), closely resembling those observed in preterm and fullterm newborn infants, could be distinguished and a detailed description is presented. The first movements were observed at 7.5 weeks postmenstrual age. A scatter of two weeks was found for the ages at which frequently occurring movement patterns could be observed for the first time. By the age of 15 weeks all 16 movement patterns could be observed. There were no major changes between 8 and 20 weeks in the appearance of the different movements, which meant that they were easy to recognize at all ages studied. A systematic assessment of position and posture showed a preference for the supine position before 16 weeks, and for the lateral position after 16 weeks. There was no consistent intra-individual preference for position or posture. Two specific motor patterns could be identified as causing either somersault or rotation around the longitudinal axis. The number of changes in fetal position increases from 10 weeks onwards, reaches a peak at 13–15 weeks and decreases after 17 weeks.

title: Yawning and associated phenomena.
abstract: In the course of some studies (1) on the vasomotor activity in human fingers I noted that definite circulatory changes occur during spontaneous yawning. An attempt to correlate these observations with existing data on yawning revealed that the few pertinent studies of this subject have not found their way into British or American publications. Although yawning and its associated phenomena appear to be of minor importance they are not without interest, and it would seem worth while to make readily available the little that is known and the rather more that has been postulated on this subject. Such is the purpose of this paper. LITERATURE. Standard sources. It is well to review the popular conceptions of yawning as set forth in the standard physiologic, psychologic and lay publications before turning to the special literature. Of the well-known text-books of physiology eight (2, 3,4, 5, 6, 7, 8, 9) contain no discussion of yawning. One of them (lo), in a section devoted to “modified respiratory movements,” defines it in the following terms:

title: Yawning induced by focal electrical stimulation in the human brain
abstract: The primary function of yawning is not fully understood. We report a case in which electrical stimulation of the putamen in the human brain consistently elicited yawning. A 46-year-old woman with intractable epilepsy had invasive depth electrode monitoring and cortical stimulation mapping as part of her presurgical epilepsy evaluation. The first two contacts of a depth electrode that was intended to sample the left insula were in contact with the putamen. Stimulation of these contacts at 6mA and 8mA consistently elicited yawning on two separate days. Engagement in arithmetic and motor tasks during stimulation did not result in yawning. When considering the role of the putamen in motor control and its extensive connectivity to cortical and brainstem regions, our findings suggest that it plays a key role in the execution of motor movements necessitated by yawning. Furthermore, given the role of the anterior insula in attention and focused tasks, activation of this area while engaged in arithmetic and motor tasks could inhibit the putaminal processing necessary for yawning. Many have hypothesized the function of yawning; however, it remains debatable whether yawning serves a primarily physiological or communicative function or perhaps both.

title: Yawning and thermoregulation
abstract: We review a growing body of medical and physiological evidence indicating that yawning may be a thermoregulatory mechanism, providing compensatory cooling when other provisions fail to operate favorably. Conditions such as multiple sclerosis, migraine headaches, epilepsy, stress and anxiety, and schizophrenia have all be linked to thermoregulatory dysfunction and are often associated with instances of atypical yawning. Excessive yawning appears to be symptomatic of conditions that increase brain and/or core temperature, such as central nervous system damage, sleep deprivation and specific serotonin reuptake inhibitors. Yawning is also associated with drowsiness, and subjective ratings of sleepiness are correlated with increases in body temperature. This view of yawning has widespread application for the basic physiological understanding of thermoregulation as well as for the improved diagnosis and treatment of diseases associated with abnormal thermoregulation.

title: Sopite syndrome: a sometimes sole manifestation of motion sickness.
abstract: Drowsiness is one of the cardinal symptoms of motion sickness; therefore, a symptom-complex centering around "drowsiness" has been identified which, for convenience, has been termed the sopite syndrome. Generally, the symptoms characterizing this syndrome are interwoven with other symptoms but under two circumstances the sopite syndrome comprises the main or sole overt manifestation of motion sickness. One circumstance is that in which the intensity of the eliciting stimuli is closely matched to a person's susceptibility, and the sopite syndrome is evoked either before other symptoms of motion sickness appear or in their absence. The second circumstance occurs during prolonged exposure in a motion environment when adaptation results in the disappearance of motion sickness symptoms, except for responses characterizing the sopite syndrome. Typical symptoms of the syndrome are: 1) yawning, 2) drowsiness, 3) disinclination for work, either physical or mental, and 4) lack of participation in group activities. Phenomena derived from an analysis of the symptomatology of the sopite syndrome are qualitatively similar but may differ quantitatively from abstractions derived in other motion sickness responses. One example is the sometimes unique time course of the sopite syndrome. This implies that the immediate eliciting mechanisms not only differ from those involved in evoking other symptoms, but, also, that they must represent first order responses. Diagnosis is difficult unless the syndrome under discussion is kept in mind. Prevention poses a greater problem than treatment.

title: Born to yawn? Cortisol linked to yawning: a new hypothesis.
abstract: Yawning has become an interesting and curious scientific conundrum. Links between several neurological disorders can be found through the commonality of yawning episodes and contagious yawning. However, the reasons why we yawn are uncertain. Cortisol levels are known to rise during stress and fatigue; yawning may occur when we are under stress or tired. We do not know whether cortisol levels fluctuate during yawning. Potentially, yawning and cortisol levels may provide a valuable diagnostic tool and warning of untoward underlying neurological problems. A new hypothesis is proposed that links cortisol levels with yawning episodes.

title: Yawning: An evolutionary perspective
abstract: Yawning is a ubiquitous activity among humans, nonhuman primates, mammals, birds and other vertebrates. Comparative analysis suggests that yawning has two major features: (1) communication — whereby the behavior of other individuals is affected, and (2) direct physiological benefit — whereby the organism is receiving some direct physiological benefit from yawning. Various functional hypotheses used to explain yawning in an evolutionary context are reviewed. The contagious nature in humans and the manifest lack of contagion in other species suggests that yawning in humans has a different and as yet poorly understood evolutionary history.

title: The daily time course of contagious and spontaneous yawning among humans
abstract: Yawning, besides being a spontaneous behavior, can also be evoked by observing others yawn. However, contagious yawning does not always occur, depending possibly on several factors, such as one’s propensity to spontaneously yawn and a heightened level of sleepiness. The aim of this study is to investigate in young adults whether contagious yawning frequency varies throughout the day, and if it is related to the daily time course of spontaneous yawning frequency and level of sleepiness. For the study, 22 subjects were instructed to log hourly, throughout wakefulness, the number of spontaneous yawns and sleepiness level. Subjects were required to continue this procedure for 3 consecutive days, after which they underwent five experimental sessions occurring at regular intervals throughout the same day. During each experimental session, subjects observed others yawn (stimulus condition) and smile (control condition). Our findings show that the contagious effect of yawning is always present throughout the daytime. Both contagious and spontaneous yawning peaked in the early morning and in the late evening, according to the sleepiness time course. However, the frequency of spontaneous yawns was remarkably lower than the frequency of contagious yawns around 19:00. This difference suggests that different mechanisms control spontaneous and contagious yawning.

title: Circadian variation of yawning behavior.
abstract: Circadian variation of spontaneous yawning is demonstrated in a line of Sprague-Dawley rats, genetically selected for high frequency of this motor pattern. Yawning is highest in late light and early dark hours, both under natural and artificial illumination. The hypothetical neurotransmitters underlying this physiological rhythm in yawning are discussed.

title: Evidence for contagious behaviors in budgerigars (Melopsittacus undulatus): An observational study of yawning and stretching
abstract: Yawning is contagious in humans and some non-human primates. If there are social functions to contagious behaviors, such as yawning, they might occur in other highly social vertebrates. To investigate this possibility, we conducted an observational study of yawning and an associated behavior, stretching, in budgerigars (Melopsittacus undulatus), a social, flock-living parrot. Flock-housed budgerigars were videotaped for 1.5h at three time-blocks during the day (early morning, afternoon and early evening), and the times of all yawns and stretches for each bird were recorded. Both yawning and stretching were temporally clumped within sessions, but were uniformly distributed across the trials of a particular time-block. This suggests that clumping was not a result of circadian patterning and that both behaviors could be contagious. There was additional evidence of contagion in stretching, which occurred in two forms - a posterior-dorsal extension of either one foot or both feet. Birds that could have observed a conspecific stretch, and that then stretched themselves within 20s, replicated the form of the earlier stretch significantly more often than expected by chance. This study provides the first detailed description of temporal patterns of yawning under social conditions in a flock-living species as well as the first support for contagious yawning and stretching in a non-primate species in a natural context. Experimental evidence will be necessary to confirm the extent of contagion in either behavior.

title: Testing yawning hypotheses in wild populations of two strepsirrhine species: Propithecus verreauxi and Lemur catta
abstract: Yawning, although easily recognized, is difficult to explain. Traditional explanations stressed physiological mechanisms, but more recently, behavioral processes have received increasing attention. This is the first study to test a range of hypotheses on yawning in wild primate populations. We studied two sympatric strepsirrhine species, Lemur catta, and Propithecus verreauxi, of the Ankoba forest (24.99°S, 46.29°E, Berenty reserve) in southern Madagascar. Sexual dimorphism is lacking in both species. However, their differences in ecological and behavioral characteristics facilitate comparative tests of hypotheses on yawning. Our results show that within each species males and females yawned with similar frequencies supporting the Dimorphism Hypothesis, which predicts that low sexual dimorphism leads to little inter‐sexual differences in yawning. In support of the State Changing Hypothesis yawning frequencies was linked to the sleep‐wake cycle and punctuated transitions from one behavior to another. Accordingly, yawning frequencies were significantly higher in L. catta than in P. verreauxi, because L. catta has a higher basal level of activity and consequently a higher number of behavioral transitions. In agreement with the Anxiety Hypothesis, yawning increased significantly in the 10 min following predatory attacks or aggression. Our findings provide the first empirical evidence of a direct connection between anxiety and yawning in lemurs. Our results show that yawning in these two strepsirrhines occurs in different contexts, but more research will be necessary to determine if yawns are a single, unitary behavior.  2015.

title: Contagious yawning and laughing: Everyday imitation- and mirror-like behavior
abstract: Infectious yawning and laughing offer a convenient, noninvasive approach to the evolution, development, production, and control of imitation-like and mirror-like phenomena in normal, behaving humans.

title: CHAPTER 9 – Contagious Yawning and Laughter: Significance for Sensory Feature Detection, Motor Pattern Generation, Imitation, and the Evolution of Social Behavior
abstract: Contagious yawning and laughter in humans offer insights into a variety of problems in the neural, behavioral, and social sciences. It does not require conscious effort for an observer to imitate a yawning or laughing person. In the language of classical ethology, these neurological stimulus detectors would be innate releasing mechanisms (IRMs) evolved to detect the releasing stimuli of yawns or laughs. Contagious behavior, thus, provides a novel, noninvasive approach to the neural basis of sensory feature detection. Data collected in the naturalistic tradition of ethology offer considerable potential for clinical research and diagnosis. Armed with baseline data concerning yawning and laughter reviewed in this chapter, one can search for conditions that vary from the normal. The chapter notes the diagnostic significance of yawning for pathologies ranging from brain tumors to hemorrhage. The study of laughter in special and clinical populations offers similar promise. This diverse sample of proposed research converges on the common theme of social communication, its neural substrates, development, evolution, pathology, and variability. The investigation of one aspect of this program illuminates the others.

title: On yawning and its functions
abstract: The forms and behavioral correlates of yawning are described, and the phylogenetic and ontogenetic aspects of the act are examined with particular attention to its possible functions. Much evidence supports the view that yawning is an important mediator of behavioral arousal levels, a view that is further strengthened by a review of endocrine, neurotransmitter, and pharmacological mechanisms of yawning: A major function of yawning appears to involve maintenance or increase of arousal when environments provide relatively little stimulation.

title: How yawning switches the default‐mode network to the attentional network by activating the cerebrospinal fluid flow
abstract: Yawning is a behavior to which little research has been devoted. However, its purpose has not yet been demonstrated and remains controversial. In this article, we propose a new theory involving the brain network that is functional during the resting state, that is, the default mode network. When this network is active, yawning manifests a process of switching to the attentional system through its capacity to increase circulation of cerebrospinal fluid (CSF), thereby increasing clearance of somnogenic factors (prostaglandin D(2), adenosine, and others) accumulating in the cerebrospinal fluid.  2014.

title: Yawning and behavioral states in premature infants.
abstract: Low risk, premature infants between 30 to 35 weeks post-conceptual age (PCA) residing in an neonatal intensive care unit environment were observed in the home incubator for spontaneous yawning from 2400 to 0500 hr. Videorecordings were analyzed for the behavioral states of quiet sleep (QS), active sleep (AS), wake (W), and drowse (D) in 3-min epochs as well as the contextual behaviors before and after yawn events using a 1-min window. Yawning periods predicted higher levels of motoric activation than nonyawn periods. Sequence analysis of preceding and following states with or without yawns were examined for stability or change. All states with or without yawn events had state stability for the preceding and following epochs, with two exceptions: 1) D state with yawning was associated with state change in the preceding 3-min epoch (most often W), and 2) D state without yawning was associated with state change in the following epoch (W or AS). Yawns were not present in QS. The results suggest that yawning is associated with increased behavioral arousal that is not state-specific. However, yawning in D state predicts state transitions in the preceding, but not the following, epoch. It is proposed that D may be an unstable state that becomes more stable when yawning is present.

title: Variation and context of yawns in captive chimpanzees (Pan troglodytes)
abstract: Primate yawns are usually categorized according to context (e.g. as a threat, anxious, or rest yawn), but there has been little consideration of whether these yawns are best regarded as a unitary behavior that only differs with respect to the context in which it is observed. This study examined the context and precise morphology of yawns in a group of 11 captive chimpanzees. Focal video sampling was used to describe the morphology and intensity of 124 yawns using ChimpFACS, a system for coding facial movements. Two distinct forms of yawn were identified, a full yawn and a yawn which is modified by additional actions that reduce the mouth aperture. These modified yawns may indicate some degree of voluntary control over facial movement in chimpanzees and, consequently, multiple functions of yawning according to context. To assess context effects, mean activity levels (resting, locomotion, and grooming) and scratching rates were compared one minute before and after each yawn. Locomotion was significantly increased following both types of yawn, whereas scratching rates significantly increased following modified yawns but decreased following full yawns. In terms of individual differences, males did not yawn more than females, although male yawns were of higher intensity, both in the degree of mouth opening and in the amount of associated head movement. These data indicate that yawning is associated with a change in activity levels in chimpanzees, but only modified yawns may be related to increased arousal. Different types of yawn can therefore be differentiated at the morphological level as well as context level.  2010.

title: Acute Physical Stress Modulates the Temporal Expression of Self-Reported Contagious Yawning in Humans
abstract: A growing number of studies on non-human animals have documented that stressors modulate the expression of yawning. In particular, recent experimental research shows that yawns are initially inhibited following physical stress, but then become potentiated thereafter. However, stress-induced yawning in humans has yet to be demonstrated experimentally. Here, we investigated the temporal relationship between self-reported contagious yawning and an acute physical stressor in 141 human subjects in the laboratory. Using a 2 × 2 between-subjects design, participants either underwent the cold pressor test (CPT) or a matched control condition prior to viewing a contagious yawning stimulus that was either displayed immediately thereafter or following a 20-min delay. Consistent with the comparative literature, we show an interaction between stress and time conditions, whereby both the incidence and frequency of yawning are lowest in the immediate-CPT trials and highest in the delayed-CPT trials. These findings support a homologous effect of acute physical stress on yawning across birds and mammals that may be related to an adaptive thermoregulatory and arousal function.

title: Yawning, acute stressors, and arousal reduction in Nazca booby adults and nestlings
abstract: Yawning is a familiar and phylogenetically widespread phenomenon, but no consensus exists regarding its functional significance. We tested the hypothesis that yawning communicates to others a transition from a state of physiological and/or psychological arousal (for example, due to action of a stressor) to a more relaxed state. This arousal reduction hypothesis predicts little yawning during arousal and more yawning (above baseline) during and after down-regulation of arousal. Experimental capture-restraint tests with wild adult Nazca boobies (Sula granti), a seabird, increased yawning frequency after release from restraint, but yawning was almost absent during tests. Natural maltreatment by non-parental adults also increased yawning by nestlings, but only after the maltreatment ended and the adult left. CORT (corticosterone) was a logical a priori element of the stress response affecting the stressor-yawning relationship under the arousal reduction hypothesis, and cannot be excluded as such for adults in capture-restraint tests but is apparently unimportant for nestlings being maltreated by adults. The arousal reduction hypothesis unites formerly disparate results on yawning: its socially contagious nature in some taxa, its clear pharmacological connection to the stress response, and its temporal linkage to transitions in arousal between consciousness and sleep.

title: Handling stress initially inhibits, but then potentiates yawning in budgerigars (Melopsittacus undulatus)
abstract: In mammals, yawning is associated with social and physiological stress, as well as thermoregulation, but little is known about why yawning occurs in stressful contexts or how it is integrated with natural stressors. To investigate the stress sensitivity of yawning in birds, we exposed budgerigars (Melopsittacus undulatus) to a handling stressor that simulated a predatory encounter. Each bird was captured, gently held for 4 min, and then released and videotaped for 1 h (experimental). On a separate day (±24 h), the undisturbed animal was videotaped for 1 h (control). The relationship between handling-induced yawning and body temperature was assessed in a separate experiment, in which the underwing temperatures of the same birds were measured at 1 min intervals during a 4 min holding period. After handling stress, yawning frequency was initially suppressed, then sharply increased within 20 min. Underwing temperature increased during handling, and individuals’ final temperatures at minute 4 were negatively correlated with their latencies to yawn after handling. Thus, stress-induced hyperthermia may be responsible for associations between yawns and stress. These results indicate that yawning may offer a sensitive, noninvasive measure of stress in birds.

title: Auditory disturbances promote temporal clustering of yawning and stretching in small groups of budgerigars (Melopsittacus undulatus).
abstract: Yawning may serve both social and nonsocial functions. When budgerigars (Melopsittacus undulatus) are briefly held, simulating capture by a predator, the temporal pattern of yawning changes. When this species is observed in a naturalistic setting (undisturbed flock), yawning and also stretching, a related behavior, are mildly contagious. On the basis of these findings, we hypothesized that a stressful event would be followed by the clustering of these behaviors in a group of birds, which may be facilitated both by a standard pattern of responding to a startling stressor and also contagion. In this study, we measured yawning and stretching in 4-bird groups following a nonspecific stressor (loud white noise) for a period of 1 hr, determining whether auditory disturbances alter the timing and frequency of these behaviors. Our results show that stretching, and to a lesser degree yawning, were nonrandomly clumped in time following the auditory disturbances, indicating that the temporal clustering is sensitive to, and enhanced by, environmental stressors while in small groups. No decrease in yawning such as found after handling stress was observed immediately after the loud noise but a similar increase in yawning 20 min after was observed. Future research is required to tease apart the roles of behavioral contagion and a time-setting effect following a startle in this species. This research is of interest because of the potential role that temporal clumping of yawning and stretching could play in both the collective detection of, and response to, local disturbances or predation threats.

title: The functional relationship between yawning and vigilance
abstract: Although yawning is a ubiquitous and phylogenetically old phenomenon, its origin and purpose remain unclear. The study aimed at testing the widely held hypothesis that yawning is triggered by drowsiness and brings about a reversal or suspension of the process of falling asleep.



Subjects complaining of excessive sleepiness were spontaneously yawning while trying to stay awake in a quiet and darkened room. Changes in their electroencephalogram (EEG) and heart rate variability (HRV) associated with yawning were compared to changes associated with isolated voluntary body movements. Special care was taken to remove eye blink- and movement-artefacts from the recorded signals.



Yawns were preceded and followed by a significantly greater delta activity in EEG than movements (p< or =0.008). After yawning, alpha rhythms were attenuated, decelerated, and shifted towards central brain regions (p< or =0.01), whereas after movements, they were attenuated and accelerated (p<0.02). A significant transient increase of HRV occurred after the onset of yawning and movements, which was followed by a significant slow decrease peaking 17s after onset (p<0.0001). No difference in HRV changes was found between yawns and movements.



Yawning occurred during periods with increased drowsiness and sleep pressure, but was not followed by a measurable increase of the arousal level of the brain. It was neither triggered nor followed by a specific autonomic activation. Our results therefore confirm that yawns occur due to sleepiness, but do not provide evidence for an arousing effect of yawning.

title: Inhibition of muscle sympathetic nerve activity during yawning
abstract: Yawning is a complex event that depends largely on the autonomic nervous system. Microneurographic techniques were used to study the mechanism involved in yawning. A series of spontaneous yawns displayed by a healthy 39-year-old male offered us the opportunity to study the muscle sympathetic nerve activity (MSNA) during this phenomenon. It was found that 2 s of yawning inhibited the MSNA recorded at the right peroneal nerve in the lateral knee area, while 3 s of slow expiration succeeding a yawn provoked an MSNA discharge. Blood pressure decreased with each slow expiration by 5–6 mmHg, and increased again with the renewed MSNA discharge. We conclude that yawning is associated with a sympathetic suppression that favours a parasympathetic dominance, as indicated by the MSNA and the decrease in blood pressure. The slow expiration following a yawn is associated with a sympathetic activation marked by an MSNA discharge and an increase in blood pressure.

title: Intracerebroventricular administration of corticotropin-releasing factor antagonist attenuates arousal response accompanied by yawning behavior in rats
abstract: We have reported that an arousal response accompanied by yawning behavior can be evoked by electrical and chemical stimulation of the hypothalamic paraventricular nucleus (PVN) in rats, although the mechanism responsible for the arousal response accompanied by yawning evoked by PVN stimulation is still unknown. In the present study, we examined the involvement of corticotropin-releasing factor (CRF) in the arousal response during yawning induced by electrical stimulation of the PVN in anesthetized, spontaneous breathing rats using intracerebroventricular (icv) injection of alpha-helical CRF, a CRF antagonist (4.2 microg, lateral ventricle). The electrocorticogram (ECoG) was recorded to evaluate arousal responses during yawning. Fast Fourier transform was used to obtain the power spectrum in delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-20 Hz) bands. We also recorded the intercostal electromyogram as an index of inspiratory activity and blood pressure (BP) as an index of autonomic function to evaluate yawning response. PVN stimulation induced significant increases in relative powers of theta, alpha, and beta bands, but not delta band, concurrent with yawning events regardless of icv injection, though the relative powers after icv injection of alpha-helical CRF were significantly lower than those after saline injection. These findings suggest that CRF neurons in the PVN are primarily responsible for the arousal response accompanied by yawning behavior.

title: Stereotyped yawning responses induced by electrical and chemical stimulation of paraventricular nucleus of the rat.
abstract: Yawning was evoked by electrical or chemical stimulation in the paraventricular nucleus (PVN) of anesthetized, spontaneously breathing rats. To evaluate physiological aspects of yawning, we monitored polygraphic measures as follows; a coordinated motor pattern of yawning was assessed by monitoring breathing [intercostal electromyogram (EMG)], mouth opening (digastric EMG), and stretching of the trunk (back EMG). We also recorded blood pressure (BP), heart rate, and the electrocorticogram (ECoG) to evaluate autonomic function and arousal responses during yawning. A stereotyped yawning response was reproducibly evoked by electrical stimulation or microinjection of -glutamate or NOC-7, a nitric oxide (NO)-releasing compound, into the PVN. The stereotyped yawning response consisted of two sequential events, an initial response represented a depressor response and an arousal shift in the ECoG to lower voltage and faster rhythms. These initial changes were followed by a yawning behavior characterized by a single large inspiration with mouth opening and stretching of the trunk. A similar sequence of events occurred during spontaneous yawning; a fall in BP and ECoG arousal preceded a yawning behavior. An increase in the frequency of spontaneous yawns was also observed after microinjection of -glutamate or NOC-7 into the PVN. Intravenous administration of NG-monomethyl--arginine, an inhibitor of nitric oxide synthase (NOS), prevented the stereotyped yawning response evoked by chemical stimulation of the PVN. Histological examination revealed that effective sites for the yawning responses were located in the medial part of the rostral PVN, the site of parvocellular and magnocellular neurons. NADPH-diaphorase histochemistry showed the existence of NOS-containing cells in yawning-evoked sites of the PVN. In summary, the sequential events of yawning may be generated by NOS-containing parvocellular neurons in the medial part of the rostral PVN projecting to the lower brain stem.

title: Light induces cortical activation and yawning in rats
abstract: We examined the effects of light stimulation on cortical activation and yawning response in anesthetized, spontaneously breathing rats. Cortical activation was assessed by means of an electrocorticogram (ECoG) and yawning response was evaluated by monitoring an intercostal electromyogram as an index of inspiratory activity and a digastric electromyogram as an indicator of mouth opening. Light stimulation elicited an arousal shift in the ECoG to faster rhythms. This arousal response was followed by a single large inspiration with mouth opening, i.e. a yawning response. Higher light intensity significantly reduced the onset latency of the arousal/yawning response. Pretreatment with pyrilamine, an H1-histamine receptor antagonist, injected into the lateral ventricle blocked both the cortical activation and the yawning response induced by light stimulation, suggesting a role of brain histaminergic neurotransmission in modulating the light-induced arousal/yawning responses.

title: Relationship between clinical endpoints for induction of anesthesia and bispectral index and effect-site concentration values.
abstract: To assess the relationship between clinical endpoints for induction of anesthesia and the electroencephalographic (EEG) bispectral index (BIS) and effect-site concentration (C(E)) values when using a target-controlled infusion (TCI) of either thiopental sodium or propofol, by hypothesizing that yawning may be a useful alternative to other commonly used clinical signs for determining loss of consciousness.



Randomized observational clinical study.



Operating room of a university-based hospital.



60 healthy adult patients (aged 20-50 yrs) scheduled for elective surgery with general anesthesia.



During a TCI of propofol (n = 30) or thiopental (n = 30), clinical endpoints for loss of verbal responsiveness (LOV), loss-of-eyelash reflex (LOE), occurrence of yawning, and apnea were assessed at 15-second intervals. In addition, BIS and C(E) values were recorded at each of the endpoints.



In both anesthetic groups, the sequence of occurrence of the clinical endpoints was similar, namely LOV, LOE, yawning, and, lastly, apnea. Compared with LOV and LOE, yawning was associated with lower BIS and higher C(E) values with both anesthetics. The frequency of yawning was higher with thiopental than propofol (83% vs. 63%, respectively). However, the frequency of apnea was higher with propofol than thiopental (77% vs. 53%, respectively).



The correlation of the clinical endpoints with BIS and C(E) values was highest for LOV. Yawning was as unreliable as LOE for determining the onset of unconsciousness during induction of anesthesia. This clinical sign failed to be observed in 17% and 37% of patients induced with thiopental and propofol, respectively.

title: Does Yawning Represent a Transient Arousal-Shift During Intravenous Induction of General Anesthesia?
abstract: Although yawning occurs frequently during the IV induction of general anesthesia, the significance of this response remains unknown. In this study, we induced 30 surgical patients with 4 mg/kg thiopental IV, and 30 patients with 2 mg/kg propofol IV. Thereafter, the occurrence of yawning was continuously assessed, as the only clinical end-point, for 1 min. The electroencephalographic bispectral index was monitored throughout the observation period. The criterion for an arousal response was a transient increase during a continuing decrease in the bispectral index value. On the basis of this criterion, the sensitivity and specificity of the yawning response as an arousal sign were 77% and 80%, respectively. If a patient exhibited a yawning response, the chance of arousal was 84% (positive predictive value). With no yawning response, the chance of nonarousal was 71% (negative predictive value). According to simple logistic regression, the yawning response was predictive of a transient arousal-shift with an odds ratio of 13.5 (95% confidence interval: 3.8–48; P < 0.001). The occurrence of a yawning response during IV induction may be a clinical indicator of a transient arousal-shift during progressive loss of consciousness.

title: Changes in Physiology before, during, and after Yawning
abstract: The ultimate function of yawning continues to be debated. Here, we examine physiological measurements taken before, during, and after yawns in humans, in an attempt to identify key proximate mechanisms associated with this behavior. In two separate studies we measured changes in heart rate, lung volume, eye closure, skin conductance, ear pulse, respiratory sinus arrhythmia, and respiratory rate. Data were depicted from 75 s before and after yawns, and analyzed at baseline, during, and immediately following yawns. Increases in heart rate, lung volume, and eye muscle tension were observed during or immediately following yawning. Patterns of physiological changes during yawning were then compared to data from non-yawning deep inhalations. In one study, respiration period increased following the execution of a yawn. Much of the variance in physiology surrounding yawning was specific to the yawning event. This was not the case for deep inhalation. We consider our findings in light of various hypotheses about the function of yawning and conclude that they are most consistent with the brain cooling hypothesis.

title: Cerebrospinal fluid flow
abstract: SummaryCerebrospinal fluid (CSF) flow in the cerebral aqueduct and spinal canal was analysed using real-time magnetic resonance imaging measurement techniques. Respiration-induced rhythmic modulation of the cardiacrelated oscillating CSF pulsation in the cerebral aqueduct and spinal canal was found. Deep inspiration was immediately followed by a marked increase in downward CSF flow in the cervical spinal canal, whereas a delay of about two heart beats was seen before downward flow from the third to the fourth ventricle increased. This pattern was also detected during yawning and was followed by a marked increase of blood flow in the internal jugular vein.

title: Last's anatomy : regional and applied
abstract: CHAPTER 1 Introduction to regional anatomy 1. Tissues and structures 1 2. Nervous system 3. Embryology 4. Anatomy of the child CHAPTER 2 Upper limb 1. Pectoral girdle 2. Shoulder 3. Axilla 4. Breast 5. Anterior compartment of the arm 6. Posterior compartment of the arm 7. Anterior compartment of the forearm 8. Posterior compartment of the forearm 9. Wrist and hand 10. Summary of upper limb innervation 11. Summary of upper limb nerve injuries 12. Osteology of the upper limb CHAPTER 3 Lower limb 1. Anterior compartment of the thigh 2. Medial compartment of the thigh 3. Gluteal region and hip joint 4. Posterior compartment of the thigh 5. Popliteal fossa and knee joint 6. Anterior compartment of the leg 7. Dorsum of the foot 8. Lateral compartment of the leg 9. Posterior compartment of the leg 10. Sole of the foot 11. Ankle and foot joints 12. Summary of lower limb innervation 13. Summary of lower limb nerve injuries 14. Osteology of the lower limb CHAPTER 4 Thorax 1. Body wall 2. Thoracic wall and diaphragm 3. Thoracic cavity 4. Superior mediastinum 5. Anterior mediastinum 6. Middle mediastinum and heart 7. Posterior mediastinum 8. Pleura 9. Lungs 10. Osteology of the thorax CHAPTER 5 Abdomen 1. Anterior abdominal wall 2. Abdominal cavity 3. Peritoneum 4. Development of the gut 5. Vessels and nerves of the gut 6. Gastrointestinal tract 7. Liver and biliary tract 8. Pancreas 9. Spleen 10. Posterior abdominal wall 11. Kidneys, ureters and suprarenal glands 12. Pelvic cavity 13. Rectum 14. Urinary bladder and ureters in the pelvis 15. Male internal genital organs 16. Female internal genital organs and urethra 17. Pelvic vessels and nerves 18. Perineum 19. Male urogenital region 20. Female urogenital region 21. Pelvic joints and ligaments 22. Summary of lumbar and sacral plexuses CHAPTER 6 Head and neck and spine 1. General topography of the neck 2. Triangles of the neck 3. Prevertebral region 4. Root of the neck 5. Face 6. Scalp 7. Parotid region 8. Infratemporal region 9. Pterygopalatine fossa 10. Nose and paranasal sinuses 11. Mouth and hard palate 12. Pharynx and soft palate 13. Larynx 14. Orbit and eye 15. Lymph drainage of head and neck 16. Temporomandibular joint 17. Ear 18. Vertebral column 19. Osteology of vertebrae 20. Cranial cavity and meninges 21. Cranial fossae 22. Vertebral canal CHAPTER 7 Central nervous system 1. Forebrain 2. Brainstem 3. Cerebellum 4. Spinal cord 5. Development of the spinal cord and brainstem nuclei 6. Summary of cranial nerves 7. Summary of cranial nerve lesions CHAPTER 8 Osteology of the skull and hyoid bone 1. Skull 2. Hyoid bone Biographical notes Index

title: Human paranasal sinuses and selective brain cooling: a ventilation system activated by yawning?
abstract: The function of the paranasal sinuses has been a controversial subject since the time of Galen, with many different theories advanced about their biological significance. For one, the paranasal sinuses have been regarded as warmers of respiratory air, when in actuality these structures appear to function in cooling the blood. In fact, human paranasal sinuses have been shown to have higher volumes in individuals living in warmer climates, and thus may be considered radiators of the brain. The literature suggests that the transfer of cool venous blood from the paranasal sinuses to the dura mater may provide a mechanism for the convection process of cooling produced by the evaporation of mucus within human sinuses. In turn, the dura mater may transmit these temperature changes, initiated by the cool venous blood from the heat-dissipating surfaces of the sinuses, to the cerebrospinal fluid compartments. Furthermore, it has recently been demonstrated in cadaveric dissections that the thin bony posterior wall of the maxillary sinus serves as an origin for both medial and lateral pterygoid muscle segments, an anatomic finding that had been previously underappreciated in the literature. The present authors hypothesize that the thin posterior wall of the maxillary sinus may flex during yawning, operating like a bellows pump, actively ventilating the sinus system, and thus facilitating brain cooling. Such a powered ventilation system has not previously been described in humans, although an analogous system has been reported in birds.

title: Yawning as a Brain Cooling Mechanism: Nasal Breathing and Forehead Cooling Diminish the Incidence of Contagious Yawning
abstract: We conducted two experiments that implicate yawning as a thermoregulatory mechanism. The first experiment demonstrates that different patterns of breathing influence susceptibility to contagious yawning. When participants were not directed how to breathe or were instructed to breathe orally (inhaling and exhaling through their mouth), the incidence of contagious yawning in response to seeing videotapes of people yawning was about 48%. When instructed to breathe nasally (inhaling and exhaling through their nose), no participants exhibited contagious yawning. In a second experiment, applying temperature packs to the forehead also influenced the incidence of contagious yawning. When participants held a warm pack (460C) or a pack at room temperature to their forehead while watching people yawn, contagious yawning occurred 41% of the time. When participants held a cold pack (40C) to their forehead, contagious yawning dropped to 9%. These findings suggest that yawning has an adaptive/functional component that it is not merely the derivative of selection for other forms of behavior.

title: Yawning and thermoregulation
abstract: Dear Editors, The paper “Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning” by Gallup andGallup [1] deals with an interesting and potentially important topic. Yet, there are problems concerning it. The patients never met the investigators, only providing subjective reports. On the basis of the two cases of pathological yawning that may be etiologically unrelated, conclusions are drawn concerning yawning in general. The medical histories contain contradictions, and no details are given concerning blood tests and MRI investigations. Both patients are reported to suffer from excessive yawning in the absence of sleep problems. Yet, both had received sleep-related diagnoses (patient 1 received diagnoses of narcolepsy and excessive daytime sleepiness—and the same diagnoses were ruled out, and patient 2 was diagnosed with sleep apnoea). A high fasting insulin level (patient 1) does not confirm insulin resistance and could result from insulinoma that causes life-threatening hypoglycaemias and would explain the symptoms (inability to walk, feeling ill, and extreme discomfort) and diagnoses (seizure, migraine, and excessive daytime sleepiness) [2–4]. It is not revealed which drug(s) worsened the problem. Metformin worsens hypoglycaemias . The alpha-1-antitrypsin deficiency of patient 2 is important (often related to emphysema/COPD) , but this goes unnoticed, and the focus is solely on the putative thermoregulatory role of her yawning. No attention is paid to her obesity and its consequences. It is not always possible to exclude multiple sclerosis at an early stage. Both patients should be encouraged to seek medical assistance. It is not sufficient that they have been “notified of the possible connection to temperature regulation”. The only measurements were performed by one patient under uncontrolled conditions and using uncontrolled methodology (no details given). Oral temperatures do not necessarily reflect core or brain temperature. What exactly is meant by saying “at the beginning and after a number of attacks” is not told, or how attacks were chosen for measurement. Subjectivity may have played a marked role, especially as the patient “can anticipate” the episodes. How she anticipates them is not reported. No conclusions should be based on these sporadic measurements. A 0.4°C decrease of body temperature of a 96.5-kg patient requires the loss of 137 kJ of heat (specific heat capacity of the body 3.56 kJ kgK ). During a 5-min bout, the body would thus act as a 460-W heater capable of heating 430 ml of water from 25°C to the boiling point in 5 min (specific heat capacity of water 4.19 kJ kgK [7, 8]). With 15 daily bouts, the extra loss of heat is over 2,000 kJ, and if not compensated for by increased heat production, severe hypothermia will result (6°C decrease daily). If compensated (without extra eating), the increased metabolism will lead to a loss of more than 2 kg of body fat in a month. The obesity of the patient is not in accord with this. Compensation by drinking hot liquids (50°C) would require a daily consumption of ca. 38 l. There are few mechanisms by which the body can lose heat so that its temperature decreases:

title: Why do we yawn? The importance of evidence for specific yawn-induced effects
abstract: Gallup (this issue) believes that our recent review on the function of yawning (Guggisberg et al., 2010) is unbalanced and that it ignores evidence for his thermoregulation hypothesis. Here we address these criticisms and show them to be untenable. While we never claimed that the social hypothesis of yawning has "definite experimental support", we emphasize the importance of experimental evidence for specific effects of yawns when considering why we yawn. The only specific effect of yawning that could be demonstrated so far is its contagiousness in humans, some non-human primates, and possibly dogs, whereas all studies investigating physiological consequences of yawns were unable to observe specific yawn-induced effects in the individual of any species. The argument that from an evolutionary perspective, yawns must have a "primitive" physiological function arises from imprecise reasoning.

title: Yawning reduces facial temperature in the high-yawning subline of Sprague-Dawley rats
abstract: BackgroundYawning is a stereotyped behavior that enhances blood flow to the skull, and the resulting counterflow has been hypothesized as a mechanism for brain cooling. Studies have shown that yawns are strongly associated with physiological and pathological conditions that increase brain temperature, and that they are followed by equivalent decreases in brain temperature. However, measured reductions in cranial or facial temperatures following yawning have yet to be reported, to our knowledge. To accomplish this, we used a subline of Sprague-Dawley rats that yawn at a much greater rate (20 yawns/h) than do outbred Sprague-Dawley rats (2 yawns/h).ResultsUsing an infrared camera, we effectively evaluated thermal changes in the cornea and concha of these rats before, during, and after yawns. The maximum temperature in both regions significantly decreased 10 s following yawns (concha: −0.3 °C, cornea: −0.4 °C), with a return to basal temperatures after 20 s.ConclusionsThis study is the first clear demonstration of yawning-induced thermal cooling on the surface of the face, providing convergent evidence that this behavior plays a functional role in thermoregulation. As other studies have demonstrated that yawning is capable of reducing cortical brain temperature, our current data support the idea that yawning functions as a thermoregulator, affecting all structures within the head.

title: Yawning and Stretching Predict Brain Temperature Changes in Rats: Support for the Thermoregulatory Hypothesis
abstract: Recent research suggests that yawning is an adaptive behavior that functions to promote brain thermoregulation among homeotherms. To explore the relationship between brain temperature and yawning we implanted thermocoupled probes in the frontal cortex of rats to measure brain temperature before, during and after yawning. Temperature recordings indicate that yawns and stretches occurred during increases in brain temperature, with brain temperatures being restored to baseline following the execution of each of these behaviors. The circulatory changes that accompany yawning and stretching may explain some of the thermal similarities surrounding these events. These results suggest that yawning and stretching may serve to maintain brain thermal homeostasis.

title: The thermoregulatory theory of yawning: what we know from over 5 years of research
abstract: Over the past 5 years numerous reports have confirmed and replicated the specific brain cooling and thermal window predictions derived from the thermoregulatory theory of yawning, and no study has found evidence contrary to these findings. Here we review the comparative research supporting this model of yawning among homeotherms, while highlighting a recent report showing how the expression of contagious yawning in humans is altered by seasonal climate variation. The fact that yawning is constrained to a thermal window of ambient temperature provides unique and compelling support in favor of this theory. Heretofore, no existing alternative hypothesis of yawning can explain these results, which have important implications for understanding the potential functional role of this behavior, both physiologically and socially, in humans and other animals. In discussion we stress the broader applications of this work in clinical settings, and counter the various criticisms of this theory.

title: Temperature-Dependent Variation in Self-Reported Contagious Yawning
abstract: The thermoregulatory theory posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. In support of this theory, previous cross-cultural research on humans has shown that self-reported contagious yawning frequency varies between seasons with distinct ambient temperature ranges. However, it remains possible that differences in yawning across seasons are a result of physiological circadian changes across the year rather than variation in ambient temperature. In an attempt to address this question, here we discuss the results of a study investigating the variation in the frequency of self-reported contagious yawning within a restricted range of a single season in one geographic location. A total of 142 pedestrians were recruited outdoors during an 18-day period over the summer in an equatorial monsoon climate in southern Florida, USA. Consistent with the thermoregulatory theory of yawning, results showed that self-reported contagious yawning frequency varied predictably across temperature gradients. This was true after statistically controlling for relative humidity, time of day, time spent outside, testing day, age of participant, and amount of sleep the night before. These findings provide further evidence suggesting a brain cooling function to yawning.

title: Contagious Yawning and Seasonal Climate Variation
abstract: Recent evidence suggests that yawning is a thermoregulatory behavior. To explore this possibility further, the frequency of contagious yawning in humans was measured while outdoors in a desert climate in the United States during two distinct temperature ranges and seasons (winter: 22°C; early summer: 37°C). As predicted, the proportion of pedestrians who yawned in response to seeing pictures of people yawning differed significantly between the two conditions (winter: 45%; summer: 24%). Across conditions yawning occurred at lower ambient temperatures, and the tendency to yawn during each season was associated with the length of time spent outside prior to being tested. Participants were more likely to yawn in the milder climate after spending long periods of time outside, while prolonged exposure to ambient temperatures at or above body temperature was associated with reduced yawning. This is the first report to show that the incidence of yawning in humans is associated with seasonal climate variation, further demonstrating that yawn-induced contagion effects can be mediated by factors unrelated to individual social characteristics or cognitive development.

title: A thermal window for yawning in humans: Yawning as a brain cooling mechanism
abstract: The thermoregulatory theory of yawning posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. Consequently, yawning should be constrained to an optimal thermal zone or range of temperature, i.e., a thermal window, in which we should expect a lower frequency at extreme temperatures. Previous research shows that yawn frequency diminishes as ambient temperatures rise and approach body temperature, but a lower bound to the thermal window has not been demonstrated. To test this, a total of 120 pedestrians were sampled for susceptibly to self-reported yawn contagion during distinct temperature ranges and seasons (winter: 1.4°C, n=60; summer: 19.4°C, n=60). As predicted, the proportion of pedestrians reporting yawning was significantly lower during winter than in summer (18.3% vs. 41.7%), with temperature being the only significant predictor of these differences across seasons. The underlying mechanism for yawning in humans, both spontaneous and contagious, appears to be involved in brain thermoregulation.

title: Ethological Study of Yawning in Primates. I. Quantitative Analysis and Study of Causation in Two Species of Old World Monkeys (Cercocebus albigena and Macaca fascicularis)
abstract: Yawning is a common, species-typical behaviour in vertebrates, generally associated with tran­ sitions from sleep to wakefulness. In primates, yawning occurs within a group in a variety of social contexts, suggesting that it has a communicative role, a hypothesis examined in this study. Yawning has rarely been studied. Quantitative studies have been concerned only with age, sex and social-status differences in yawning f!-equency. The causation and function of yawning were examined in a quantitative, 796-h ethological analysis of observations of two groups of Cercocebus albigena and one group of Macaca fascicularis. In both species, yawns occurred in two main contexts: during transitions from rest to activity (the 'rest yawn') and following social interactions (the 'emotion yawn'). The rest yawn represents 90 % of yawns and is common to every age-sex group. By contrast, the emotion yawn (10 %) is more frequent in adult males. Regardless of context, yawning was more frequent in males than females. Within males yawning frequency increased with age. Thus, sex hormones may modulate the physiologie al processes involved. Yawns were usually performed by individuals in seated, lying or standing positions. Yawns were frequently followed by short periods of rest, so that, when triggered by a social interaction, they occurred at its end. The morphology of the yawning act did not vary in regard to context age and / or sex of the yawner.

title: The Influence of Age, Sex, and Rank on Yawning Behavior in Two Species of Macaques (Macaca fascicularis and M. fuscata)
abstract: Yawning behavior was studied in two species of macaques: the long-tailed macaque (Macaca fascicularis) and the Japanese macaque (M. fuscata). Japanese macaques yawned much more than long-tailed macaques. Age, sex, and dominance rank exerted different effects on yawning in the two species. In the long-tailed macaques, sex differences in frequency of yawning emerged only after sexual maturity; yawning rates increased significantly in both males and females as they reached sexual maturity; and, among males, dominance rank was positively correlated with frequency of yawning. Differently, in the Japanese macaques, males, both mature and immature, yawned more than same-aged females; sexual maturity was associated with an increase in yawning in males only; and male rank did not correlate with the frequency of yawning. Regardless of interspecific differences, the overall results supported only in part the finding that, in Old World monkeys, yawning is largely influenced by plasma concentrations of androgens. There was evidence that social factors were also important in influencing the age-sex class distribution of yawning.

title: Do men yawn more than women
abstract: The aim of this study was to test the hypothesis that sex differences in primate yawning are related to size dimorphism in canine teeth. Data were collected on yawning by a primate species ( Homo sapiens ) in which the two sexes differ only slightly in canine size. Unlike more dimorphic primates, human males and females did not differ in the frequency of yawning, although uncovered yawns were more frequent in men than in women.

title: Why do we yawn? Primitive versus derived features
abstract: Guggisberg et al. (2010) reviewed the evidence for the origin and function of yawning, and conclude that theories describing a physiological role lack support. Instead, they argue research supports the notion that yawning has a communicative function. Contrary to the authors' claim that the social/communication hypothesis has the "best experimental evidence", there is in fact no definitive experimental support for the predictions of this model. Furthermore, the authors claim to take an evolutionary perspective, but sufficient examples across the comparative (non-primate) literature are missing, and they fail to acknowledge phylogenic history. Due to the ubiquity of this behavior across vertebrates, and the regularity of its occurrence in a number of different physiological states and social contexts, it is likely that instead of serving one purpose, yawning is multifunctional across a number of species. The most parsimonious explanation for the origin of yawning suggests that any social value is a derived feature, while the primitive feature or function is physiological. The current paper addresses these concerns, and identifies a number of other weaknesses in the social/communication hypothesis as a global explanation for the origin and function of yawning.

title: Contagious yawning in autistic and typical development.
abstract: The authors tested susceptibility to contagious yawning in 120 children, 1-6 years, to identify the time course of its emergence during development. Results indicated a substantial increase in the frequency of contagious yawning at 4 years. In a second study, the authors examined contagious yawning in 28 children with autism spectrum disorders (ASD), 6-15 years. Children with ASD showed diminished susceptibility to contagious yawning compared with 2 control groups matched for mental and chronological age, respectively. In addition, children diagnosed with Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS) a milder variant of autism, were more susceptible to contagious yawning than were children diagnosed with full Autistic Disorder. The authors explore the implications of these findings for theories about the development of mimicry and emotional contagion.

title: Young Children Display Contagious Yawning When Looking at the Eyes
abstract: Although contagious yawning occurs commonly in adulthood, previous studies reported it to be uncommon in children below 4-5 years. However, these studies did not regulate eye contact, a factor that can induce contagious yawning. We therefore investigated whether a cue to make eye contact would influence contagious yawning, particularly in young children. Fifty-six children between the ages of 3 and 16 watched video clips of models either yawning or opening their mouths. Contagious yawning was observed from the age of 3 years, and was negatively correlated with age. Whereas children older than 8 years caught yawns only after the yawning clips, children under the age of 8 years yawned contagiously following both yawn and control clips. Additionally, frequent imitation occurred in children below the age of 8 years. Poor general attention skills or reduced attention to specific facial features (e.g. the eyes) may be responsible for the reduced yawn contagion previously described in young children.

title: Gaze following in the red-footed tortoise (Geochelone carbonaria)
abstract: Gaze following refers to the ability of an animal to orient its gaze direction to that of another organism. Such a behavior may be adaptive as it alerts the observer to important objects in the environment such as food or predators. This behavior has been shown in mammals and birds, but the evolutionary history and the distribution of this behavior throughout the animal kingdom remain unclear. Here, we show that a reptile, the red-footed tortoise (Geochelone carbonaria), is able to follow the gaze of a conspecific in a lookup task. Controls revealed that neither the mere presence of a conspecific nor the presentation of a light stimulus (without a demonstrator present) controlled the tortoises’ behavior. The findings indicate that the ability to follow gaze may be found in mammals, birds and reptiles and could have evolved before the amniotic line diverged, or may result from a general ability to learn.

title: No evidence of contagious yawning in the red-footed tortoise Geochelone carbonaria
abstract: Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining conta- gious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli: the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions: observation of conditioned yawn, non demonstra- tion control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions: real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes (Current Zoology 57 (4): 477-484, 2011).

title: Contagious yawning: the role of self-awareness and mental state attribution.
abstract: Contagious yawning is a common, but poorly understood phenomenon. We hypothesized that contagious yawning is part of a more general phenomenon known as mental state attribution (i.e. the ability to inferentially model the mental states of others). To test this hypothesis we compared susceptibility to contagiously yawn with performance on a self-face recognition task, several theory of mind stories, and on a measure of schizotypal personality traits. Consistent with the hypothesis, susceptibility to contagiously yawn was positively related to performance on self-face recognition and faux pas theory of mind stories, and negatively related to schizotypal personality traits. These data suggest that contagious yawning may be associated with empathic aspects of mental state attribution and are negatively affected by increases in schizotypal personality traits much like other self-processing related tasks.

title: Contagious yawning and the brain.
abstract: Contagious yawning, the onset of a yawn triggered by seeing, hearing, reading, or thinking about another person yawn is a well-documented phenomenon. The mechanisms that drive contagious yawning are as yet unknown, but there is recent evidence of a link between contagious yawning and self-processing (S.M. Platek, S.R. Critton, T.E. Myers, G.G. Gallup Jr., Contagious yawning: the role of self-awareness and mental state attribution,  (2003) 223-227.) that is negatively impacted by schizotypal personality traits. The neural substrates involved in contagious yawning, however, are unknown. Here, using fMRI, we show that viewing someone yawn evokes unique neural activity in the posterior cingulate and precuneus. Because of the role these areas play in self-processing (e.g., self-referential processing, theory of mind, autobiographical memory), our findings provide further support for the hypothesis that contagious yawning may be part of a neural network involved in empathy.

title: Contagious yawning in gelada baboons as a possible expression of empathy
abstract: Yawn contagion in humans has been proposed to be related to our capacity for empathy. It is presently unclear whether this capacity is uniquely human or shared with other primates, especially monkeys. Here, we show that in gelada baboons (Theropithecus gelada) yawning is contagious between individuals, especially those that are socially close, i.e., the contagiousness of yawning correlated with the level of grooming contact between individuals. This correlation persisted after controlling for the effect of spatial association. Thus, emotional proximity rather than spatial proximity best predicts yawn contagion. Adult females showed precise matching of different yawning types, which suggests a mirroring mechanism that activates shared representations. The present study also suggests that females have an enhanced sensitivity and emotional tuning toward companions. These findings are consistent with the view that contagious yawning reveals an emotional connection between individuals. This phenomenon, here demonstrated in monkeys, could be a building block for full-blown empathy.

title: Empathy for Pain Involves the Affective but not Sensory Components of Pain
abstract: pulsars is about 1.8 mJy (1 Jy 10 W m Hz) at 1390 MHz (Table 1), compared with a total flux density at this frequency of 7 mJy (3). The 5-mJy unpulsed emission probably arises in the impact region described above. We find it remarkable, with much of the magnetosphere of B blown away by the wind of A, that B still works as a pulsar. This suggests that the radio emission is probably generated close to the neutron star, providing a direct constraint on the emission height.  We have detected the binary companion of the millisecond pulsar J0737 3039 as a pulsar, making this the first known double-pulsar system. This discovery confirms the neutron-star nature of the companions to recycled pulsars in eccentric binary systems and validates the suggested evolutionary sequences in which a companion star, having spun up the pulsar, forms a young pulsar in a supernova explosion (31). The highly relativistic nature of this compact system opens up opportunities for much more stringent tests of relativistic gravitation than have been possible previously. Not only have we already measured four quantities attributable to, and consistent with, general relativity, but the mass ratio R is a new high-precision constraint that is independent of gravitational theories. Within a year or so, we expect to measure the orbital decay due to emission of gravitational radiation. If the intrinsic value due to gravitational-wave damping can be extracted, it will allow tests of radiative aspects of gravitational theories mixed with strong-field effects. On somewhat longer time scales of a few years, we expect to detect several other relativistic effects, such as geodetic precession of the pulsars’ spin axes, spinorbit coupling, and other deviations, making this a superb test bed for relativity. The detection of the companion as a pulsar also opens up the possibility of using each pulsar to probe the magnetosphere of the other. The energy flux from the millisecond pulsar is strongly affecting the pulse emission process in the companion, and eclipses of the millisecond pulsar by the companion are also seen. Future measurements of orbital variations in pulse shapes, amplitudes, polarization, and timing over a range of radio frequencies will give fascinating insights into magnetospheric processes in pulsars.

title: Yawning. A homeostatic reflex and its psychological significance.
abstract: Yawning is a common phenomenon that is an expression of certain physiological and psychological states, yet it bas received remarkably little attention in the medical literature. Dumpert (1921), Hauptmann (1920), and Lewy (1921) reached some conclusions regarding the nature of yawning in connection with observations of patients with encephalitis lethargica; however, after the 1920s the subject was again disregarded. On the basis of certain clinical and experimental observations which may have some psychiatric significance and which, to my knowledge, have not yet been described, a review of the matter of yawning appeared justified.

title: Mammalian empathy: behavioural manifestations and neural basis
abstract: Recent research on empathy in humans and other mammals seeks to dissociate emotional and cognitive empathy. These forms, however, remain interconnected in evolution, across species and at the level of neural mechanisms. New data have facilitated the development of empathy models such as the perception–action model (PAM) and mirror-neuron theories. According to the PAM, the emotional states of others are understood through personal, embodied representations that allow empathy and accuracy to increase based on the observer's past experiences. In this Review, we discuss the latest evidence from studies carried out across a wide range of species, including studies on yawn contagion, consolation, aid-giving and contagious physiological affect, and we summarize neuroscientific data on representations related to another's state.

title: Yawning: Effects of stimulus interest
abstract: The hypothesis that subjects yawn more while observing uninteresting than while observing interesting stimuli was tested by comparing the yawns produced by 17- to 19-year-old college freshmen while they observed a 30-min rock video, a complex and interesting audiovisual stimulus, and a 30-min color-bar test pattern without an audio track, an unchanging and very uninteresting stimulus. Significantly more and longer yawns were produced during the uninteresting than during the interesting stimulus and males performed longer yawns than females. The folk belief that people yawn more during boring than interesting events was confirmed.

title: IMITATION IN ANIMALS: EVIDENCE, FUNCTION, AND MECHANISMS
abstract: The terms sociallearning and social influence have been used descriptively and theoretically to characterize a broad range of animal behavior from physical antipredatory adaptations such as eye spots, which are totally under genetic control, to the human capacity for the exaggeration of individual characteristics, known as caricature, which are largely under cognitive control. In the present review, the various forms of social influence and social learning are identified and distinghished from imitation, a term that generally has been reserved for behavioral matching that cannot be accounted for using simpler specifically predisposed, motivational, or learning mechanisms. It is suggested that much of the ambiguity in the literature concerning the various forms of social learning can be attributed to the distinction between the function of a behavior and the mechanisms responsible for its occurrence. Finally, the various mechanisms that have been proposed to account for imitative learning are presented and an attempt is made to evaluate them.

title: Neural basis of contagious itch and why some people are more prone to it
abstract: Watching someone scratch himself can induce feelings of itchiness in the perceiver. This provides a unique opportunity to characterize the neural basis of subjective experiences of itch, independent of changes in peripheral inputs. In this study, we first established that the social contagion of itch is essentially a normative response (experienced by most people), and that the degree of contagion is related to trait differences in neuroticism (i.e., the tendency to experience negative emotions), but not to empathy. Watching video clips of someone scratching (relative to control videos of tapping) activated, as indicated by functional neuroimaging, many of the neural regions linked to the physical perception of itch, including anterior insular, primary somatosensory, and prefrontal (BA44) and premotor cortices. Moreover, activity in the left BA44, BA6, and primary somatosensory cortex was correlated with subjective ratings of itchiness, and the responsivity of the left BA44 reflected individual differences in neuroticism. Our findings highlight the central neural generation of the subjective experience of somatosensory perception in the absence of somatosensory stimulation. We speculate that the habitual activation of this central “itch matrix” may give rise to psychogenic itch disorders.

title: Observing conspecifics scratching induces a contagion of scratching in Japanese monkeys (Macaca fuscata).
abstract: Although a large number of studies have examined self-directed behaviors (SDBs) such as scratching and self-grooming as nonverbal leakage of negative emotional arousal in humans, few studies have investigated the informative function of SDBs in nonhuman primates. The present study investigated whether viewing another monkey scratching itself elicited negative arousal from conspecific observers in Japanese monkeys (Macaca fuscata). An experimental situation was created in which the target monkey watched a stranger through a small peephole and the observer monkey(s) watched the target in turn. Scratching spread when conspecific observers watched the target scratching itself while performing monitoring behavior. The author proposes that the possible contagion of scratching by monkeys observing another's scratching may involve transmission of a psychological state, a primitive style of empathy.

title: Mirror Sniffing: Humans Mimic Olfactory Sampling Behavior
abstract: Ample evidence suggests that social chemosignaling plays a significant role in human behavior. Processing of odors and chemosignals depends on sniffing. Given this, we hypothesized that humans may have evolved an automatic mechanism driving sniffs in response to conspecific sniffing. To test this, we measured sniffing behavior of human subjects watching the movie Perfume, which contains many olfactory sniffing events. Despite the total absence of odor, observers sniffed when characters in the movie sniffed. Moreover, this effect was most pronounced in scenes where subjects heard the sniff but did not see the sniffed-at object. We liken this response to the orienting towards conspecific gaze in vision and argue that its robustness further highlights the significance of olfactory information processing in human behavior.

title: Catch the wave: prairie dogs assess neighbours’ awareness using contagious displays
abstract: The jump–yip display of black-tailed prairie dogs (Cynomys ludovicianus) is contagious, spreading through a prairie dog town as ‘the wave’ through a stadium. Because contagious communication in primates serves to assess conspecific social awareness, we investigated whether instigators of jump–yip bouts adjusted their behaviour relative to the response of conspecifics recruited to display bouts. Increased responsiveness of neighbouring town members resulted in bout initiators devoting a significantly greater proportion of time to active foraging. Contagious jump–yips thus function to assess neighbours’ alertness, soliciting social information to assess effective conspecific group size in real time and reveal active probing of conspecific awareness consistent with theory of mind in these group-living rodents.

title: An Observational Investigation of Behavioral Contagion in Common Marmosets (Callithrix jacchus): Indications for Contagious Scent-Marking
abstract: Behavioral contagion is suggested to promote group coordination that may facilitate activity transitions, increased vigilance, and state matching. Apart from contagious yawning, however, very little attention has been given to this phenomenon, and studies on contagious yawning in primates have so far only focused on Old World monkeys and apes. Here we studied behavioral contagion in common marmosets, a species for which group coordination and vigilance are paramount. In particular, we investigated the contagiousness of yawning, stretching, scratching, tongue protrusion, gnawing, and scent-marking. We coded these behaviors from 14 adult marmosets, from two different social groups. During testing sessions, animals were separated into groups of four individuals for 20-min observation periods, across three distinct diurnal time points (morning, midday, and afternoon) to test for circadian patterns. We observed almost no yawning (0.12 yawns/h) and very little stretching behavior. For all other behaviors, which were more common, we found several temporal and inter-individual differences (i.e., sex, age, dominance status) predictive of these responses. Moreover, we found that gnawing and scent-marking, which almost always co-occurred as a fixed-action pattern, were highly temporally clustered within observation sessions. We discuss the relative absence of yawning in marmosets as well as the possible function of contagious scent-marking, and provide suggestions for future research into the proximate and ultimate functions of these behaviors in marmosets.

title: Sub-adult Ravens Synchronize their Play : A Case of Emotional Contagion?
abstract: Emotional contagion – the alignment of emotions between individuals through behavioral synchronization – is proposed as a key, basic component of human social cognition and empathy. In the field of cognitive zoology, contagious behaviors have also received attention. Several such behaviors have been documented in various species. Nevertheless, emotional and behavioral contagion differ. Emotional contagion – a term predominantly used in human psychology – requires that the contagious behavior leads to converging emotional states. In non-linguistic animals, it is difficult to determine whether a behavior “caught” from someone else results in a similar affective state or remains a purely behavioral response. Some studies suggest the latter as a possibility. To disentangle the problem, we explored instances of contagious behaviors within the play domain. In several species, play involves a variety of behaviors falling into different categories: social, object and locomotor play. If a category of play in one individual induces a different category of play in another, this suggests the spread of a generally playful mood rather than a species-specific motor response. Although some studies suggest emotional contagion in mammals, it is not known whether it occurs in birds. We investigated play contagion in a group of ravens, well known for their complex social skills. The results indicate emotional contagion: the birds engaged in all categories of play on a higher level under the condition where contagion was likely to occur.

title: Positive emotional contagion in a New Zealand parrot
abstract: Positive emotional contagions are outwardly emotive actions that spread from one individual to another, such as glee in preschool children  or laughter in humans of all ages . The play vocalizations of some animals may also act as emotional contagions. For example, artificially deafened rats are less likely to play than their non-hearing-impaired conspecifics, while no such effect is found for blinded rats . As rat play vocalizations are also produced in anticipation of play, they, rather than the play itself, may act as a contagion, leading to a hypothesis of evolutionary parallels between rat play vocalizations and human laughter . The kea parrot (Nestor notabilis) has complex play behaviour and a distinct play vocalization . We used acoustic playback to investigate the effect of play calls on wild kea, finding that play vocalizations increase the amount of play among both juveniles and adults, likely by acting as a positive emotional contagion.

title: Monkey see, monkey do: contagious itch in nonhuman primates.
abstract: "Contagious itch" has been anecdotally reported and recently confirmed in a controlled setting in humans. Here, we investigated in adult rhesus macaques whether 'contagious itch' occurs spontaneously in monkeys. In a first experiment, the latency to scratch following cage-mate scratching was observed in pair-housed adult rhesus macaques. Scratching increased within the first 60 s and subsequently declined. In a second experiment, scratching behavior was recorded for individually caged adult rhesus macaques which where shown videos of monkeys scratching, but also neutral stimuli. A greater frequency of scratching was observed when monkeys viewed a video sequence of another monkey scratching as well as during the neutral stimulus immediately following the monkey scratching segment. In conclusion, viewing other monkeys scratching significantly increased scratching behavior in adult rhesus macaques.

title: Molecular and neural basis of contagious itch behavior in mice
abstract: To scratch or not to scratch Observing someone else scratching themselves can make you want to do so. This contagious itching has been observed in monkeys and humans, but what about rodents? Yu et al. found that mice do imitate scratching when they observe it in other mice. The authors identified a brain area called the suprachiasmatic nucleus as a key circuit for mediating contagious itch. Gastrin-releasing peptide and its receptor in the suprachiasmatic nucleus were necessary and sufficient to transmit this contagious behavior. Science, this issue p. 1072 Suprachiasmatic neural circuits control contagious itching. Socially contagious itch is ubiquitous in human society, but whether it exists in rodents is unclear. Using a behavioral paradigm that does not entail prior training or reward, we found that mice scratched after observing a conspecific scratching. Molecular mapping showed increased neuronal activity in the suprachiasmatic nucleus (SCN) of the hypothalamus of mice that displayed contagious scratching. Ablation of gastrin-releasing peptide receptor (GRPR) or GRPR neurons in the SCN abolished contagious scratching behavior, which was recapitulated by chemogenetic inhibition of SCN GRP neurons. Activation of SCN GRP/GRPR neurons evoked scratching behavior. These data demonstrate that GRP-GRPR signaling is necessary and sufficient for transmitting contagious itch information in the SCN. The findings may have implications for our understanding of neural circuits that control socially contagious behaviors.

title: Measuring individual differences in empathy: Evidence for a multidimensional approach.
abstract: To facilitate a multidimensional approach to empathy the Interpersonal Reactivity Index (IRI) includes 4 subscales: Perspective-Taking (PT) Fantasy (FS) Empathic Concern (EC) and Personal Distress (PD). The aim of the present study was to establish the convergent and discriminant validity of these 4 subscales. Hypothesized relationships among the IRI subscales between the subscales and measures of other psychological constructs (social functioning self-esteem emotionality and sensitivity to others) and between the subscales and extant empathy measures were examined. Study subjects included 677 male and 667 female students enrolled in undergraduate psychology classes at the University of Texas. The IRI scales not only exhibited the predicted relationships among themselves but also were related in the expected manner to other measures. Higher PT scores were consistently associated with better social functioning and higher self-esteem; in contrast Fantasy scores were unrelated to these 2 characteristics. High EC scores were positively associated with shyness and anxiety but negatively linked to egotism. The most substantial relationships in the study involved the PD scale. PD scores were strongly linked with low self-esteem and poor interpersonal functioning as well as a constellation of vulnerability uncertainty and fearfulness. These findings support a multidimensional approach to empathy by providing evidence that the 4 qualities tapped by the IRI are indeed separate constructs each related in specific ways to other psychological measures.

title: Putting the Altruism Back into Altruism: The Evolution of Empathy
abstract: Evolutionary theory postulates that altruistic behavior evolved for the return-benefits it bears the performer. For return-benefits to play a motivational role, however, they need to be experienced by the organism. Motivational analyses should restrict themselves, therefore, to the altruistic impulse and its knowable consequences. Empathy is an ideal candidate mechanism to underlie so-called directed altruism, i.e., altruism in response to anothers's pain, need, or distress. Evidence is accumulating that this mechanism is phylogenetically ancient, probably as old as mammals and birds. Perception of the emotional state of another automatically activates shared representations causing a matching emotional state in the observer. With increasing cognition, state-matching evolved into more complex forms, including concern for the other and perspective-taking. Empathy-induced altruism derives its strength from the emotional stake it offers the self in the other's welfare. The dynamics of the empathy mechanism agree with predictions from kin selection and reciprocal altruism theory.

title: The Empathy Quotient: An Investigation of Adults with Asperger Syndrome or High Functioning Autism, and Normal Sex Differences
abstract: Empathy is an essential part of normal social functioning, yet there are precious few instruments for measuring individual differences in this domain. In this article we review psychological theories of empathy and its measurement. Previous instruments that purport to measure this have not always focused purely on empathy. We report a new self-report questionnaire, the Empathy Quotient (EQ), for use with adults of normal intelligence. It contains 40 empathy items and 20 filler/control items. On each empathy item a person can score 2, 1, or 0, so the EQ has a maximum score of 80 and a minimum of zero. In Study 1 we employed the EQ with n = 90 adults (65 males, 25 females) with Asperger Syndrome (AS) or high-functioning autism (HFA), who are reported clinically to have difficulties in empathy. The adults with AS/HFA scored significantly lower on the EQ than n = 90 (65 males, 25 females) age-matched controls. Of the adults with AS/HFA, 81% scored equal to or fewer than 30 points out of 80, compared with only 12% of controls. In Study 2 we carried out a study of n = 197 adults from a general population, to test for previously reported sex differences (female superiority) in empathy. This confirmed that women scored significantly higher than men. The EQ reveals both a sex difference in empathy in the general population and an empathy deficit in AS/HFA.

title: Generalized deficit in all core components of empathy in schizophrenia
abstract: Empathy is a multidimensional construct composed of several components such as emotion recognition, emotional perspective taking and affective responsiveness. Patients with schizophrenia demonstrate deficits in several domains of emotion processing and perspective taking, thus suggesting a dysfunctional emotional competence. We assessed empathic abilities via three paradigms measuring emotion recognition, perspective taking and affective responsiveness as well as self-report empathy questionnaires in 24 (12 females, 12 males) schizophrenia patients meeting the DSM-IV criteria for schizophrenia and 24 matched healthy volunteers. Patients were recruited from the Department of Psychiatry and Psychotherapy, RWTH Aachen University and healthy volunteers were recruited via advertisement. Groups were matched for age, gender and parental education. Data analysis indicates a significant empathic deficit in patients, reflected in worse performance in all three domains. This deficit was only partly reflected in the self-report empathy questionnaires. Comparing the different tasks, emotional perspective taking was the most difficult task for all subjects and symptomatology worsened affective responsiveness. Schizophrenia patients not only struggle to correctly identify emotions, but also have difficulties in spontaneously simulating another person's subjective world (perspective taking) and might not be able to respond adequately in terms of their own emotional experience (affective responsiveness), which are not caused by emotion perception deficits. The results suggest that all domains of empathy are affected in schizophrenia and have to be addressed independently in behavioral therapies, thereby offering a possibility to improve socio-occupational life.

title: Contagious and spontaneous yawning in autistic and typically developing children
abstract: Previous studies have reported the absence of a contagious effect when autistic children view another’s yawning. This result could be due to the difficulty of autistic children in establishing reciprocal gaze behaviour with human partners. Furthermore, the presence of a contagious effect in autistic children could change according their degree of functioning. We evaluated the contagious effect of yawning in both autistic children with different degrees of functioning and in typically developing children exposed to the viewing and hearing of others yawn. Furthermore the frequency and the daily distribution of spontaneous yawning were evaluated and compared among three groups. Autism Spectrum Disorder can selectively affect some behaviour. In autistic children the contagious effect of yawning is largely impaired, whereas the spontaneous production and daily distribution are not. These results support the hypothesis of a link between contagious yawning and social abilities and the existence of different processes underlying spontaneous and contagious yawning.

title: Absence of contagious yawning in children with autism spectrum disorder
abstract: This study is the first to report the disturbance of contagious yawning in individuals with autism spectrum disorder (ASD). Twenty-four children with ASD as well as 25 age-matched typically developing (TD) children observed video clips of either yawning or control mouth movements. Yawning video clips elicited more yawns in TD children than in children with ASD, but the frequency of yawns did not differ between groups when they observed control video clips. Moreover, TD children yawned more during or after the yawn video clips than the control video clips, but the type of video clips did not affect the amount of yawning in children with ASD. Current results suggest that contagious yawning is impaired in ASD, which may relate to their impairment in empathy. It supports the claim that contagious yawning is based on the capacity for empathy.

title: Empathy in schizophrenia: impaired resonance
abstract: Resonance is the phenomenon of one person unconsciously mirroring the motor actions as basis of emotional expressions of another person. This shared representation serves as a basis for sharing physiological and emotional states of others and is an important component of empathy. Contagious laughing and contagious yawning are examples of resonance. In the interpersonal contact with individuals with schizophrenia we can often experience impaired empathic resonance. The aim of this study is to determine differences in empathic resonance—in terms of contagion by yawning and laughing—in individuals with schizophrenia and healthy controls in the context of psychopathology and social functioning. We presented video sequences of yawning, laughing or neutral faces to 43 schizophrenia outpatients and 45 sex- and age-matched healthy controls. Participants were video-taped during the stimulation and rated regarding contagion by yawning and laughing. In addition, we assessed self-rated empathic abilities (Interpersonal Reactivity Index), psychopathology (Positive and Negative Syndrome Scale in the schizophrenia group resp. Schizotypal Personality Questionnaire in the control group), social dysfunction (Social Dysfunction Index) and executive functions (Stroop, Fluency). Individuals with schizophrenia showed lower contagion rates for yawning and laughing. Self-rated empathic concern showed no group difference and did not correlate with contagion. Low rate of contagion by laughing correlated with the schizophrenia negative syndrome and with social dysfunction. We conclude that impaired resonance is a handicap for individuals with schizophrenia in social life. Blunted observable resonance does not necessarily reflect reduced subjective empathic concern.

title: Brief Report: Does Eye Contact Induce Contagious Yawning in Children with Autism Spectrum Disorder?
abstract: Individuals with autism spectrum disorder (ASD) reportedly fail to show contagious yawning, but the mechanism underlying the lack of contagious yawning is still unclear. The current study examined whether instructed fixation on the eyes modulates contagious yawning in ASD. Thirty-one children with ASD, as well as 31 age-matched typically developing (TD) children, observed video clips of either yawning or control mouth movements. Participants were instructed to fixate to the eyes of the face stimuli. Following instructed fixation on the eyes, both TD children and children with ASD yawned equally frequently in response to yawning stimuli. Current results suggest that contagious yawning could occur in ASD under an experimental condition in which they are instructed to fixate on the yawning eyes.

title: Presence of Contagious Yawning in Children with Autism Spectrum Disorder
abstract: Most previous studies suggest diminished susceptibility to contagious yawning in children with autism spectrum disorder (ASD). However, it could be driven by their atypical attention to the face. To test this hypothesis, children with ASD and typically developing (TD) children were shown yawning and control movies. To ensure participants' attention to the face, an eye tracker controlled the onset of the yawning and control stimuli. Results demonstrated that both TD children and children with ASD yawned more frequently when they watched the yawning stimuli than the control stimuli. It is suggested therefore that the absence of contagious yawning in children with ASD, as reported in previous studies, might relate to their weaker tendency to spontaneously attend to others' faces.

title: Male Yawning Is More Contagious than Female Yawning among Chimpanzees (Pan troglodytes)
abstract: Yawn contagion is not restricted to humans and has also been reported for several non-human animal species, including chimpanzees (Pan troglodytes). Contagious yawning may lead to synchronisation of behaviour. However, the function of contagious yawning is relatively understudied. In this study, we investigated the function of contagious yawning by focusing on two types of signal providers: close social associates and leaders. We provided a captive chimpanzee colony with videos of all individuals of their own group that were either yawning, or at rest. Consistent with other studies, we demonstrated that yawning is contagious for chimpanzees, yet we did not find any effect of relationship quality on yawn contagion. However, we show that yawn contagion is significantly higher when the video model is a yawning male than when the video model was a yawning female, and that this effect is most apparent among males. As males are dominant in chimpanzee societies, male signals may be more relevant to the rest of the group than female signals. Moreover, since chimpanzees form male-bonded societies, male signals are especially relevant for other males. Therefore, we suggest that the sex-differences of yawning contagion among chimpanzees reflect the function of yawning in the synchronisation of behaviour.

title: In Bonobos Yawn Contagion Is Higher among Kin and Friends
abstract: In humans, the distribution of yawn contagion is shaped by social closeness with strongly bonded pairs showing higher levels of contagion than weakly bonded pairs. This ethological finding led the authors to hypothesize that the phenomenon of yawn contagion may be the result of certain empathic abilities, although in their most basal form. Here, for the first time, we show the capacity of bonobos (Pan paniscus) to respond to yawns of conspecifics. Bonobos spontaneously yawned more frequently during resting/relaxing compared to social tension periods. The results show that yawn contagion was context independent suggesting that the probability of yawning after observing others' yawns is not affected by the propensity to engage in spontaneous yawns. As it occurs in humans, in bonobos the yawing response mostly occurred within the first minute after the perception of the stimulus. Finally, via a Linear Mixed Model we tested the effect of different variables (e.g., sex, rank, relationship quality) on yawn contagion, which increased when subjects were strongly bonded and when the triggering subject was a female. The importance of social bonding in shaping yawn contagion in bonobos, as it occurs in humans, is consistent with the hypothesis that empathy may play a role in the modulation of this phenomenon in both species. The higher frequency of yawn contagion in presence of a female as a triggering subject supports the hypothesis that adult females not only represent the relational and decisional nucleus of the bonobo society, but also that they play a key role in affecting the emotional states of others.

title: Monkeys Pay Per View: Adaptive Valuation of Social Images by Rhesus Macaques
abstract: Individuals value information that improves decision making. When social interactions complicate the decision process, acquiring information about others should be particularly valuable. In primate societies, kinship, dominance, and reproductive status regulate social interactions and should therefore systematically influence the value of social information, but this has never been demonstrated. Here, we show that monkeys differentially value the opportunity to acquire visual information about particular classes of social images. Male rhesus macaques sacrificed fluid for the opportunity to view female perinea and the faces of high-status monkeys but required fluid overpayment to view the faces of low-status monkeys. Social value was highly consistent across subjects, independent of particular images displayed, and only partially predictive of how long subjects chose to view each image. These data demonstrate that visual orienting decisions reflect the specific social content of visual information and provide the first experimental evidence that monkeys spontaneously discriminate images of others based on social status.

title: Yawn Contagion and Empathy in Homo sapiens
abstract: The ability to share others' emotions, or empathy, is crucial for complex social interactions. Clinical, psychological, and neurobiological clues suggest a link between yawn contagion and empathy in humans (Homo sapiens). However, no behavioral evidence has been provided so far. We tested the effect of different variables (e.g., country of origin, sex, yawn characteristics) on yawn contagion by running mixed models applied to observational data collected over 1 year on adult (>16 years old) human subjects. Only social bonding predicted the occurrence, frequency, and latency of yawn contagion. As with other measures of empathy, the rate of contagion was greatest in response to kin, then friends, then acquaintances, and lastly strangers. Related individuals (r≥0.25) showed the greatest contagion, in terms of both occurrence of yawning and frequency of yawns. Strangers and acquaintances showed a longer delay in the yawn response (latency) compared to friends and kin. This outcome suggests that the neuronal activation magnitude related to yawn contagion can differ as a function of subject familiarity. In conclusion, our results demonstrate that yawn contagion is primarily driven by the emotional closeness between individuals and not by other variables, such as gender and nationality.

title: Yawn contagion in humans and bonobos: emotional affinity matters more than species
abstract: In humans and apes, yawn contagion echoes emotional contagion, the basal layer of empathy. Hence, yawn contagion is a unique tool to compare empathy across species. If humans are the most empathic animal species, they should show the highest empathic response also at the level of emotional contagion. We gathered data on yawn contagion in humans (Homo sapiens) and bonobos (Pan paniscus) by applying the same observational paradigm and identical operational definitions. We selected a naturalistic approach because experimental management practices can produce different psychological and behavioural biases in the two species, and differential attention to artificial stimuli. Within species, yawn contagion was highest between strongly bonded subjects. Between species, sensitivity to others’ yawns was higher in humans than in bonobos when involving kin and friends but was similar when considering weakly-bonded subjects. Thus, emotional contagion is not always highest in humans. The cognitive components concur in empowering emotional affinity between individuals. Yet, when they are not in play, humans climb down from the empathic podium to return to the “understory”, which our species shares with apes.

title: Seeing two faces together: preference formation in humans and rhesus macaques
abstract: Humans, great apes and old world monkeys show selective attention to faces depending on conspecificity, familiarity, and social status supporting the view that primates share similar face processing mechanisms. Although many studies have been done on face scanning strategy in monkeys and humans, the mechanisms influencing viewing preference have received little attention. To determine how face categories influence viewing preference in humans and rhesus macaques (Macaca mulatta), we performed two eye-tracking experiments using a visual preference task whereby pairs of faces from different species were presented simultaneously. The results indicated that viewing time was significantly influenced by the pairing of the face categories. Humans showed a strong bias towards an own-race face in an Asian–Caucasian condition. Rhesus macaques directed more attention towards non-human primate faces when they were paired with human faces, regardless of the species. When rhesus faces were paired with faces from Barbary macaques (Macaca sylvanus) or chimpanzees (Pan troglodytes), the novel species’ faces attracted more attention. These results indicate that monkeys’ viewing preferences, as assessed by a visual preference task, are modulated by several factors, species and dominance being the most influential.

title: Macaques attend to scratching in others
abstract: Self-directed behaviours in primates as a response to increasing psychological or physiological stress are a well-studied phenomenon. There is some evidence that these behaviours can be contagious when observed by conspecifics, but the adaptive function of this process is unclear. The ability to perceive stress in others and respond to it could be an important part of sustaining cohesiveness in social primates, but spontaneously acquiring stress-related behaviours (and potentially emotional states) from all group mates via contagion could be maladaptive. To investigate this, a group of captive Barbary macaques, Macaca sylvanus, were presented with videos of conspecifics engaging in self-directed behaviour (scratching) and neutral behaviour. Behavioural responses as a result of exposure to the stimuli were compared (1) between familiar and unfamiliar individuals, and (2) within familiar individuals to consider the modulating effects of social relationships. Our results did not show contagious scratching in this species. However, there were differences in how individuals attended to the scratching stimuli. Subjects were more attentive to scratching videos than to neutral videos and familiar than unfamiliar individuals. Within the familiar individuals, subjects were more attentive to those to whom they were weakly bonded. We suggest that increased attention to scratching behaviours may be adaptive in order to monitor and avoid stressed group mates, whose subsequent behaviour may be unpredictable and aggressive. Monitoring group mates who are not allies may also be adaptive as they may pose the biggest risk. These findings will help increase our understanding of subtle cues that can be communicative in primates, and also the evolutionary steps towards understanding others.

title: Patterns of Social Attention in Mandrills, Mandrillus sphinx
abstract: Primates possess impressive cognitive abilities, especially in the social domain, and accumulate knowledge about their social environment. Studying how primates distribute their attention among group mates may help us understand how they obtain their social knowledge and what they consider as the most relevant social stimuli. We conducted 11 month of observations on glance rates in a captive group of 15 mandrills (Mandrillus sphinx). We investigated the factors affecting inter- and intraindividual variation in the attention paid to group mates. The total amount of attention given to group mates was related to the age, but not to the sex or the dominance rank of the subject. Mandrills looked more at high-ranking than at low-ranking group mates and more at their own kin than at nonkin. Furthermore, the attention directed to both the aggressor and its victim increased markedly after an aggressive episode. These results show mandrills actively monitor their group mates, thus presumably gaining valuable social information, and suggest that studying patterns of social attention may help to understand primate social knowledge and decision making.

title: Individual Variation in Contagious Yawning Susceptibility Is Highly Stable and Largely Unexplained by Empathy or Other Known Factors
abstract: The contagious aspect of yawning is a well-known phenomenon that exhibits variation in the human population. Despite the observed variation, few studies have addressed its intra-individual reliability or the factors modulating differences in the susceptibility of healthy volunteers. Due to its obvious biological basis and impairment in diseases like autism and schizophrenia, a better understanding of this trait could lead to novel insights into these conditions and the general biological functioning of humans. We administered 328 participants a 3-minute yawning video stimulus, a cognitive battery, and a comprehensive questionnaire that included measures of empathy, emotional contagion, circadian energy rhythms, and sleepiness. Individual contagious yawning measurements were found to be highly stable across testing sessions, both in a lab setting and if administered remotely online, confirming that certain healthy individuals are less susceptible to contagious yawns than are others. Additionally, most individuals who failed to contagiously yawn in our study were not simply suppressing their reaction, as they reported not even feeling like yawning in response to the stimulus. In contrast to previous studies indicating that empathy, time of day, or intelligence may influence contagious yawning susceptibility, we found no influence of these variables once accounting for the age of the participant. Participants were less likely to show contagious yawning as their age increased, even when restricting to ages of less than 40 years. However, age was only able to explain 8% of the variability in the contagious yawn response. The vast majority of the variability in this extremely stable trait remained unexplained, suggesting that studies of its inheritance are warranted.

title: Contagious yawning and psychopathy
abstract: Psychopathy is characterized by a general antisocial lifestyle with behaviors including being selfish, manipulative, impulsive, fearless, callous, possibly domineering, and particularly lacking in empathy. Contagious yawning in our species has been strongly linked to empathy. We exposed 135 students, male and female, who completed the Psychopathic Personality Inventory-Revised (PPI-R), to a yawning paradigm intended to induce a reactionary yawn. Further, we exposed males to an emotion-related startle paradigm meant to assess peripheral amygdalar reactivity. We found that scores on the PPI-R subscale Coldheartedness significantly predicted a reduced chance of yawning. Further, we found that emotion-related startle amplitudes were predictive of frequency of contagious yawning. These data suggest that psychopathic traits may be related to the empathic nature of contagious yawning in our species.

title: Civil Inattention Exists—in Elevators
abstract: Elevators were used as a field setting to examine the existence of civil inattention (Goffman, 1963)—the rule that in a transient encounter strangers give visual notice to each other and then withdraw attention. In Sutdy 1, confederates recorded the behavior of single riders in elevators. It was found that about half of all riders gave the confederate a brief visual notice at the beginning of the ride and then refrained from further eye contact. Of the riders, 35% added one or two glances to the initial look; perhaps these riders wanted to renew their acknowledgment of the confederates or perhaps they simply displayed more interest in their fellow passengers. In two more investigations (Study 2 and an exact replication—Study 3) confederates shared elevators with single riders and either followed or violated the rule of civil inattention. In the former they glanced at the subject and then withdrew all further attention; in the latter case they either avoided eye contact altogether or stared at the subject for the duration of the ride. It was found that behaviors consistent with the rule of civil inattention were rated more favorably than those in violation of the rule. The conditions under which civil inattention may be modified or eliminated were discussed.

title: Potential social interactions are important to social attention
abstract: Social attention, or how spatial attention is allocated to biologically relevant stimuli, has typically been studied using simplistic paradigms that do not provide any opportunity for social interaction. To study social attention in a complex setting that affords social interaction, we measured participants’ looking behavior as they were sitting in a waiting room, either in the presence of a confederate posing as another research participant, or in the presence of a videotape of the same confederate. Thus, the potential for social interaction existed only when the confederate was physically present. Although participants frequently looked at the videotaped confederate, they seldom turned toward or looked at the live confederate. Ratings of participants’ social skills correlated with head turns to the live, but not videotaped, confederate. Our results demonstrate the importance of studying social attention within a social context, and suggest that the mere opportunity for social interaction can alter social attention.

title: The role of attention and familiarity in face identification
abstract: How is attention allocated during face identification? Previous work using famous and unfamiliar faces suggests that either no attention or a special attentional mechanism is required. We used a conventional attentional blink (AB) procedure to measure face identification with temporarily reduced attention. The participants viewed a rapid series of face images with one embedded nonface abstract pattern (T1). They judged the texture of T1 and then detected a prespecified face (T2) presented at varying lags after T1. T2 was either famous or unfamiliar, as were distractor faces. Regardless of distractor type, detection of an unfamiliar T2 face was significantly impaired at short versus long T1-T2 lags, indicating an attentional requirement for face identification. Detection of a famous T2 face was unaffected by lag, suggesting that familiarity protects against a temporal attentional bottleneck. These findings do not support propositions that face identification is ”special” in its need for attentional control.

title: Effects of familiarity on the perceptual integrality of the identity and expression of faces: the parallel-route hypothesis revisited.
abstract: The effects of familiarity on selective attention for the identity and expression of faces were tested using Garner's speeded-classification task. In 2 experiments, participants classified expression (or identity) of familiar and unfamiliar faces while the irrelevant dimension of identity (or expression) was either held constant (baseline condition) or varied randomly (filtering condition). Selective attention was measured by the difference in performance between these 2 conditions. Failure of selective attention was larger for familiar than for unfamiliar faces. In addition, failure of selective attention was found both for identity and for expression judgments. These findings show that familiarity increases (he perceptual integrality between identity and expression, and they question previous studies arguing that identity judgments are always resistant to irrelevant variations in expression. The authors suggest that the systems processing identity and expression are interconnected in that facial identity serves as a reference from which expressions can be more easily derived.

title: Same-race faces are perceived more holistically than other-race faces
abstract: People are better at recognizing samethan other-race faces but the theoretical explanation of this phenomenon is still controversial. Here we tested the hypothesis that the ‘‘other-race effect’’ is related to a reduced ability to encode configural information on other-race faces. Caucasian and Asian participants had to match whole faces to isolated facial features, or onto whole faces differing by a single feature, on both Caucasian and Asian faces. Participants performed better with whole faces as compared to isolated features, demonstrating a ‘‘holistic processing’’ of faces (Tanaka & Farah, 1993). For Caucasian participants, this ‘‘whole/ part advantage’’ was observed only for Caucasian faces. Asian participants who had been living for about a year among Caucasians had a comparable whole/part advantage regardless the race of the faces. These results indicate that same-race faces are processed more holistically than other-race faces, as a result of experience. However, despite processing Caucasian faces as holistically as Asian faces in this paradigm, Asian subjects still presented a large other-race effect. This observation suggests that holistic encoding may be a necessary step in order to be able to recognize other-race faces efficiently, but that it is by no means sufficient to overcome the other-race face effect.

title: High familiarity enhances visual change detection for face stimuli
abstract: Does high familiarity with a face enable particularly efficient visual processing? In three experiments, we presented briefly and successively two pairs of faces (either famous or recently learned), masking each presentation. Between the first and the second presentations, one face changed, and the task was to locate this change. Performance was significantly better when the change involved a famous face. Thissuperfamiliarity effect was found only for changes occurring in the left visual field and was abolished by inverting the faces. Extended prior study of the recently learned faces did not improve performance with these stimuli. The results suggest that superfamiliarity promotes highly efficient visual processing and may especially activate a configural mode of analysis.

title: Social Modulation of Contagious Yawning in Wolves
abstract: On the basis of observational and experimental evidence, several authors have proposed that contagious yawn is linked to our capacity for empathy, thus presenting a powerful tool to explore the root of empathy in animal evolution. The evidence for the occurrence of contagious yawning and its link to empathy, however, is meagre outside primates and only recently domestic dogs have demonstrated this ability when exposed to human yawns. Since dogs are unusually skilful at reading human communicative behaviors, it is unclear whether this phenomenon is deeply rooted in the evolutionary history of mammals or evolved de novo in dogs as a result of domestication. Here we show that wolves are capable of yawn contagion, suggesting that such ability is a common ancestral trait shared by other mammalian taxa. Furthermore, the strength of the social bond between the model and the subject positively affected the frequency of contagious yawning, suggesting that in wolves the susceptibility of yawn contagion correlates with the level of emotional proximity. Moreover, female wolves showed a shorter reaction time than males when observing yawns of close associates, suggesting that females are more responsive to their social stimuli. These results are consistent with the claim that the mechanism underlying contagious yawning relates to the capacity for empathy and suggests that basic building blocks of empathy might be present in a wide range of species.

title: Familiarity Bias and Physiological Responses in Contagious Yawning by Dogs Support Link to Empathy
abstract: In humans, the susceptibility to yawn contagion has been theoretically and empirically related to our capacity for empathy. Because of its relevance to evolutionary biology, this phenomenon has been the focus of recent investigations in non-human species. In line with the empathic hypothesis, contagious yawning has been shown to correlate with the level of social attachment in several primate species. Domestic dogs (Canis familiaris) have also shown the ability to yawn contagiously. To date, however, the social modulation of dog contagious yawning has received contradictory support and alternative explanations (i.e., yawn as a mild distress response) could explain positive evidence. The present study aims to replicate contagious yawning in dogs and to discriminate between the two possible mediating mechanisms (i.e., empathic vs. distress related response). Twenty-five dogs observed familiar (dog’s owner) and unfamiliar human models (experimenter) acting out a yawn or control mouth movements. Concurrent physiological measures (heart rate) were additionally monitored for twenty-one of the subjects. The occurrence of yawn contagion was significantly higher during the yawning condition than during the control mouth movements. Furthermore, the dogs yawned more frequently when watching the familiar model than the unfamiliar one demonstrating that the contagiousness of yawning in dogs correlated with the level of emotional proximity. Moreover, subjects’ heart rate did not differ among conditions suggesting that the phenomenon of contagious yawning in dogs is unrelated to stressful events. Our findings are consistent with the view that contagious yawning is modulated by affective components of the behavior and may indicate that rudimentary forms of empathy could be present in domesticated dogs.

title: Auditory contagious yawning in domestic dogs (Canis familiaris): first evidence for social modulation
abstract: Dogs’ capacity to ‘catch’ human yawns has recently attracted the attention of researchers in the field of animal cognition. Following recent studies suggesting that contagion yawning in humans, and some other primates, is empathy-related, some authors have considered the possibility that the same mechanism may underlie contagious yawning in dogs. To date, however, no positive evidence has been found, and more parsimonious hypotheses have been put forward. The present study explored the ‘contagion-only’ hypothesis by testing whether the mere sound of a human yawn can be sufficient to elicit yawning in dogs, in a way that is unaffected by social–emotional factors. Unexpectedly, results showed an interesting interplay between contagion and social effects. Not only were dogs found to catch human yawns, but they were also found to yawn more at familiar than unfamiliar yawns. Although not allowing for conclusive inferences about the mechanisms underlying contagious yawning in dogs, this study provides first data that renders plausible empathy-based, emotionally connected, contagious yawning in these animals.

title: Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy
abstract: Humans favor others seen as similar to themselves (ingroup) over people seen as different (outgroup), even without explicitly stated bias. Ingroup-outgroup bias extends to involuntary responses, such as empathy for pain. However, empathy biases have not been tested in our close primate relatives. Contagious yawning has been theoretically and empirically linked to empathy. If empathy underlies contagious yawning, we predict that subjects should show an ingroup-outgroup bias by yawning more in response to watching ingroup members yawn than outgroup. Twenty-three chimpanzees (Pan troglodytes) from two separate groups watched videos of familiar and unfamiliar individuals yawning or at rest (control). The chimpanzees yawned more when watching the familiar yawns than the familiar control or the unfamiliar yawns, demonstrating an ingroup-outgroup bias in contagious yawning. These results provide further empirical support that contagious yawning is a measure of empathy, which may be useful for evolutionary biology and mental health.

title: Chimpanzees empathize with group mates and humans, but not with baboons or unfamiliar chimpanzees
abstract: Human empathy can extend to strangers and even other species, but it is unknown whether non-humans are similarly broad in their empathic responses. We explored the breadth and flexibility of empathy in chimpanzees, a close relative of humans. We used contagious yawning to measure involuntary empathy and showed chimpanzees videos of familiar humans, unfamiliar humans and gelada baboons (an unfamiliar species). We tested whether each class of stimuli elicited contagion by comparing the effect of yawn and control videos. After including previous data on the response to ingroup and outgroup chimpanzees, we found that familiar and unfamiliar humans elicited contagion equal to that of ingroup chimpanzees. Gelada baboons did not elicit contagion, and the response to them was equal to that of outgroup chimpanzees. However, the chimpanzees watched the outgroup chimpanzee videos more than any other. The combination of high interest and low contagion may stem from hostility towards unfamiliar chimpanzees, which may interfere with an empathic response. Overall, chimpanzees showed flexibility in that they formed an empathic connection with a different species, including unknown members of that species. These results imply that human empathic flexibility is shared with related species.

title: Neither infants nor toddlers catch yawns from their mothers
abstract: This study aimed to clarify whether infants and preschool children show susceptibility to contagious yawning, a well-known effect that has been demonstrated experimentally in older children and adults by exposing them to video sequences showing yawns. In a first study, parents kept a log of their child's yawns for a one week period. None of the log entries reported any contagious yawns by the children. Although less frequent than in older children and adults, spontaneous yawning by infants and preschoolers showed the typical morning, post-wakening peak, and an increase before bedtime in the evening. In an experimental study, infants and preschoolers watched a presentation that included many images of yawning and a repeated video clip of their own mother yawning, but there was no evidence of contagious yawning. The results suggest that, even when witnessing yawns by someone with whom they have a strong and positive emotional relationship, very young children do not show contagious yawning.

title: Mirror self-image reactions before age two.
abstract: The behavior of 88 children between 3 and 24 months was observed before a mirror, using an objective technique to examine the child's awareness of the image as his own. The results indicate the following age-related sequence of behavior before the mirror: the first prolonged and repeated reaction of an infant to his mirror image is that of a sociable “playmate” from about 6 through 12 months of age. In the second year of life wariness and withdrawal appeared; self-admiring and embarrassed behavior accompanied those avoidance behaviors starting at 14 months, and was shown by 75% of the subjects after 20 months of age. During the last part of the second year of life, from 20 to 24 months of age, 65% of the subjects demonstrated recognition of their mirror images.

title: Does the autistic child have a “theory of mind” ?
abstract: We use a new model of metarepresentational development to predict a cognitive deficit which could explain a crucial component of the social impairment in childhood autism. One of the manifestations of a basic metarepresentational capacity is a ‘theory of mind’. We have reason to believe that autistic children lack such a ‘theory’. If this were so, then they would be unable to impute beliefs to others and to predict their behaviour. This hypothesis was tested using Wimmer and Perner's puppet play paradigm. Normal children and those with Down's syndrome were used as controls for a group of autistic children. Even though the mental age of the autistic children was higher than that of the controls, they alone failed to impute beliefs to others. Thus the dysfunction we have postulated and demonstrated is independent of mental retardation and specific to autism.

title: Three-year-olds' difficulty with false belief: The case for a conceptual deficit
abstract: The hypothesis, that a conceptual limitation underlies 3-year-olds' difficulty with false-belief attribution (Wimmer & Perner, 1983), was tested against three competing hypotheses. These were: (1) failure to retain essential facts, (2) failure to understand the normal expectations which give rise to false belief and (3) pragmatic misinterpretation of the test question. Results showed that false-belief attribution remained difficult for younger 3-year-olds despite their retention of essential facts and despite attempts to make expectations more explicit and prevent pragmatic misinterpretation. These findings strengthen the original hypothesis, specified here as the inability to assign conflicting truth values to propositions. This hypothesis can explain why 3-year-olds find pretend play, the distinction between expected and achieved outcomes, the real-imaginary distinction and level 1 perspective taking easier to understand than false belief, the reality-appearance distinction and level 2 perspective taking.

title: Great apes anticipate that other individuals will act according to false beliefs
abstract: Apes understand false beliefs We humans tend to believe that our cognitive skills are unique, not only in degree, but also in kind. The more closely we look at other species, however, the clearer it becomes that the difference is one of degree. Krupenye et al. show that three different species of apes are able to anticipate that others may have mistaken beliefs about a situation (see the Perspective by de Waal). The apes appear to understand that individuals have different perceptions about the world, thus overturning the human-only paradigm of the theory of mind. Science, this issue p. 110; see also p. 39 Apes recognize that others may have false beliefs.  Humans operate with a “theory of mind” with which they are able to understand that others’ actions are driven not by reality but by beliefs about reality, even when those beliefs are false. Although great apes share with humans many social-cognitive skills, they have repeatedly failed experimental tests of such false-belief understanding. We use an anticipatory looking test (originally developed for human infants) to show that three species of great apes reliably look in anticipation of an agent acting on a location where he falsely believes an object to be, even though the apes themselves know that the object is no longer there. Our results suggest that great apes also operate, at least on an implicit level, with an understanding of false beliefs.

title: Lifespan development of attentiveness in domestic dogs: drawing parallels with humans
abstract: Attention is pivotal to consciousness, perception, cognition, and working memory in all mammals, and therefore changes in attention over the lifespan are likely to influence development and aging of all of these functions. Due to their evolutionary and developmental history, the dog is being recognized as an important species for modeling human healthspan, aging and associated diseases. In this study, we investigated the normal lifespan development of attentiveness of pet dogs in naturalistic situations, and compared the resulting cross-sectional developmental trajectories with data from previous studies in humans. We tested a sample of 145 Border collies (6 months to 14 years) with humans and objects or food as attention attractors, in order to assess their attentional capture, sustained and selective attention, and sensorimotor abilities. Our results reveal differences in task relevance in sustained attentional performance when watching a human or a moving object, which may be explained by life-long learning processes involving such stimuli. During task switching we found that dogs’ selective attention and sensorimotor abilities showed differences between age groups, with performance peaking at middle age. Dogs’ sensorimotor abilities showed a quadratic distribution with age and were correlated with selective attention performance. Our results support the hypothesis that the development and senescence of sensorimotor and attentional control may be fundamentally interrelated. Additionally, attentional capture, sustained attention, and sensorimotor control developmental trajectories paralleled those found in humans. Given that the development of attention is similar across humans and dogs, we propose that the same regulatory mechanisms are likely to be present in both species. Finally, this cross-sectional study provides the first description of age group changes in attention over the lifespan of pet dogs.

title: Cognition through the lifespan: mechanisms of change
abstract: Cognitive abilities rise steeply from infancy to young adulthood and then are either maintained or decline to old age, depending on the specific ability. This pattern suggests corresponding continuities of mechanism and process, but it is striking that the fields of cognitive development and cognitive aging make little contact with each other's methods and theories. In this review we examine reasons for this cultural separation, and show how recent findings from both areas fit a framework couched in terms of cognitive representation and control. These two broad factors have very different lifespan trajectories; consideration of their relative growth and decline makes it clear that cognitive aging is not simply 'development in reverse'. This framework is offered in light of recent interest in finding greater continuity throughout the lifespan and creating a more comprehensive explanation of cognitive function and cognitive change.

title: Feature-selective attention: Evidence for a decline in old age
abstract: Although attention in older adults is an active research area, feature-selective aspects have not yet been explicitly studied. Here we report the results of an exploratory study involving directed changes in feature-selective attention. The stimuli used were two random dot kinematograms (RDKs) of different colours, superimposed and centrally presented. A colour cue with random onset after the beginning of each trial instructed young and older subjects to attend to one of the RDKs and detect short intervals of coherent motion while ignoring analogous motion events in the non-cued RDK. Behavioural data show that older adults could detect motion, but discriminated target from distracter motion less reliably than young adults. The method of frequency tagging allowed us to separate the EEG responses to the attended and ignored stimuli and directly compare steady-state visual evoked potential (SSVEP) amplitudes elicited by each stimulus before and after cue onset. We found that younger adults show a clear attentional enhancement of SSVEP amplitude in the post-cue interval, while older adults' SSVEP responses to attended and ignored stimuli do not differ. Thus, in situations where attentional selection cannot be spatially resolved, older adults show a deficit in selection that is not shared by young adults.

title: Bridging a yawning chasm: EEG investigations into the debate concerning the role of the human mirror neuron system in contagious yawning
abstract: Ongoing debate in the literature concerns whether there is a link between contagious yawning and the human mirror neuron system (hMNS). One way of examining this issue is with the use of the electroencephalogram (EEG) to measure changes in mu activation during the observation of yawns. Mu oscillations are seen in the alpha bandwidth of the EEG (8–12 Hz) over sensorimotor areas. Previous work has shown that mu suppression is a useful index of hMNS activation and is sensitive to individual differences in empathy. In two experiments, we presented participants with videos of either people yawning or control stimuli. We found greater mu suppression for yawns than for controls over right motor and premotor areas, particularly for those scoring higher on traits of empathy. In a third experiment, auditory recordings of yawns were compared against electronically scrambled versions of the same yawns. We observed greater mu suppression for yawns than for the controls over right lateral premotor areas. Again, these findings were driven by those scoring highly on empathy. The results from these experiments support the notion that the hMNS is involved in contagious yawning, emphasise the link between contagious yawning and empathy, and stress the importance of good control stimuli.

title: Mirror neuron activity during contagious yawning—an fMRI study
abstract: Yawning is contagious. However, little research has been done to elucidate the neuronal representation of this phenomenon. Our study objective was to test the hypothesis that the human mirror neuron system (MNS) is activated by visually perceived yawning. We used functional magnetic resonance imaging to assess brain activity during contagious yawning (CY). Signal-dependent changes in blood oxygen levels were compared when subjects viewed videotapes of yawning faces as opposed to faces with a neutral expression. In response to yawning, subjects showed unilateral activation of their Brodmann’s area 9 (BA 9) portion of the right inferior frontal gyrus, a region of the MNS. In this way, two individuals could share physiological and associated emotional states based on perceived motor patterns. This is one component of empathy (motor empathy) that underlies the development of cognitive empathy. The BA 9 is reportedly active in tasks requiring mentalizing abilities. Our results emphasize the connection between the MNS and higher cognitive empathic functions, including mentalizing. We conclude that CY is based on a functional substrate of empathy.

title: Functional imaging of face and hand imitation: towards a motor theory of empathy
abstract: Empathy requires the ability to map the feelings of others onto our own nervous system. Until recently, there was no plausible mechanism to explain how such a mapping might occur. The discovery of mirror neurons, however, suggests that the nervous system is capable of mapping the observed actions of others onto the premotor cortex of the self, at least for reaching and grasping movements. Is there a mirroring system for emotive actions, such as facial expression? Subjects (N = 15; all right-handed; eight men, seven women) watched movies of facial expressions (smile or frown) and hand movements (move index or middle finger) while brain activity was imaged using functional magnetic resonance imaging (fMRI). Subjects watched the movies under three different conditions: passive viewing, active imitation, and an active motor control. Subjects also performed a verb generation task to functionally identify language-processing areas. We found evidence for a common cortical imitation circuit for both face and hand imitation, consisting of Broca's area, bilateral dorsal and ventral premotor areas, right superior temporal gyrus (STG), supplementary motor area, posterior temporo-occipital cortex, and cerebellar areas. For faces, passive viewing led to significant activation in the right ventral premotor area, whereas imitation produced bilateral activation. This result is consistent with evidence for right hemisphere (RH) dominance for emotional processing, and suggests that there may be a right hemisphere mirroring system that could provide a neural substrate for empathy.

title: Understanding motor events: a neurophysiological study
abstract: SummaryNeurons of the rostral part of inferior premotor cortex of the monkey discharge during goal-directed hand movements such as grasping, holding, and tearing. We report here that many of these neurons become active also when the monkey observes specific, meaningful hand movements performed by the experimenters. The effective experimenters' movements include among others placing or retrieving a piece of food from a table, grasping food from another experimenter's hand, and manipulating objects. There is always a clear link between the effective observed movement and that executed by the monkey and, often, only movements of the experimenter identical to those controlled by a given neuron are able to activate it. These findings indicate that premotor neurons can retrieve movements not only on the basis of stimulus characteristics, as previously described, but also on the basis of the meaning of the observed actions.

title: The role of shared neural activations, mirror neurons, and morality in empathy – A critical comment
abstract: In the last decade, the phenomenon of empathy has received widespread attention by the field of social neuroscience. This has provided fresh insights for theoretical models of empathy, and substantially influenced the academic and public conceptions about this complex social skill. The present paper highlights three key issues which are often linked to empathy, but which at the same time might obscure our understanding of it. These issues are: (1) shared neural activations and whether these can be interpreted as evidence for simulation accounts of empathy; (2) the causal link of empathy to our presumed mirror neuron system; and (3) the question whether increasing empathy will result in better moral decisions and behaviors. The aim of our review is to provide the basis for critically evaluating our current understanding of empathy, and its public reception, and to inspire new research directions.

title: Yearning to yawn: the neural basis of contagious yawning
abstract: Watching another person yawn may trigger us to do the same. Here we studied brain activation with functional magnetic resonance imaging (fMRI) while subjects watched videotaped yawns. Significant increases in the blood oxygen level dependent (BOLD) signal, specific to yawn viewing as contrasted to viewing non-nameable mouth movements, were observed in the right posterior superior temporal sulcus (STS) and bilaterally in the anterior STS, in agreement with the high affinity of STS to social cues. However, no additional yawn-specific activation was observed in Broca's area, the core region of the human mirror-neuron system (MNS) that matches action observation and execution. Thus, activation associated with viewing another person yawn seems to circumvent the essential parts of the MNS, in line with the nature of contagious yawns as automatically released behavioural acts-rather than truly imitated motor patterns that would require detailed action understanding. The subjects' self-reported tendency to yawn covaried negatively with activation of the left periamygdalar region, suggesting a connection between yawn contagiousness and amygdalar activation.

title: Contagious yawning and the frontal lobe: An fMRI study
abstract: We conducted a slow event‐related fMRI experiment with naïve subjects' passively viewing yawn and various other control videos along with correlative behavioral testing. Specifically associated with the viewing of the contagious yawn was an area of activation in the ventromedial prefrontal cortex. These findings suggest a role for the prefrontal cortex in the processing of contagious yawning, while demonstrating a unique automaticity in the processing of contagious motor programs which take place independently of mirror neuron networks.

title: An investigation of auditory contagious yawning
abstract: Despite a widespread familiarity with the often compelling urge to yawn after perceiving someone else yawn, an understanding of the neural mechanism underlying contagious yawning remains incomplete. In the present auditory fMRI study, listeners used a 4-point scale to indicate how much they felt like yawning following the presentation of a yawn, breath, or scrambled yawn sound. Not only were yawn sounds given significantly higher ratings, a trait positively correlated with each individual’s empathy measure, but relative to control stimuli, random effects analyses revealed enhanced hemodynamic activity in the right posterior inferior frontal gyrus (pIFG) in response to hearing yawns. Moreover, pIFG activity was greatest for yawn stimuli associated with high as opposed to low yawn ratings and for control sounds associated with equally high yawn ratings. These results support a relationship between contagious yawning and empathy and provide evidence for pIFG involvement in contagious yawning. A supplemental figure for this study may be downloaded from http://cabn.psychonomic-journals.org/content/supplemental.

title: Mental Mechanisms: Philosophical Perspectives on Cognitive Neuroscience
abstract: Naturalism and Mechanism: Outlines of a New Philosophy of Science. From Mental Phenomena to  Delineating and Decomposing Memory. From Working Parts to Operations: Decomposing and Resynthesizing Visual Processing. Reduction and Independence of Higher- Representations and Mental Mechanisms. From Responsive to Active Mechanisms. Confronting Mechanism's Critics: Accounting for Freedom and Dignity via Mental Mechanisms.

title: Brain activation associated with evaluative processes of guilt and embarrassment: an fMRI study
abstract: We aimed to investigate the neural substrates associated with evaluative process of moral emotions. Using functional magnetic resonance imaging (fMRI), we examined the similarities and differences between evaluative process of guilt and that of embarrassment at the neural basis level. Study of the neural basis of judgments of moral emotions might contribute to a better understanding of the amoral behavior observed in neurological and psychiatric disorders. Nineteen healthy volunteers were studied. The participants read sentences carrying neutral, guilty, or embarrassing contents during the scans. Both guilt and embarrassment conditions commonly activated the medial prefrontal cortex (MPFC), left posterior superior temporal sulcus (STS), and visual cortex. Compared to guilt condition, embarrassment condition produced greater activation in the right temporal cortex (anterior), bilateral hippocampus, and visual cortex. Most of these regions have been implicated in the neural substrate of social cognition or Theory of Mind (ToM). Our results support the idea that both are self-conscious emotions, which are social emotions requiring the ability to represent the mental states of others. At the same time, our functional fMRI data are in favor of the notion that evaluative process of embarrassment might be a more complex process than that of guilt.

title: Towards a neuroscience of empathy: Ontogeny, phylogeny, brain mechanisms, context and psychopathology
abstract: Empathy allows individuals to share the affective states of others, predict others' actions, and stimulate prosocial behavior. Whilst the proximate mechanisms of empathy, modulated in part by neuropeptides such as oxytocin, control the ways we interact with our social environment, the ultimate causes seem to have arisen along with the mechanisms involved in mammalian parental care. The conceptual boundaries of empathy, however, have been blurred by definitional inaccuracies of mechanisms that can be regarded as phylogenetic precursors or physiological prerequisites for empathy, including mimicry and emotion contagion. Contextual factors such as early experiences with primary care-givers (attachment), current mood states and other environmental contingencies are capable of modulating empathy. Moreover, evidence suggests that there is also a "dark side" of empathy, namely envy and schadenfreude (gloating) that are elicited by social comparison, competition and ingroup-outgroup distinction. This review aims at clarifying some of the open definitional questions related to empathy, and emphasizing the need for considering contextual factors in the study of empathy in both normal and abnormal psychology.

title: Oxytocin Conditions Intergroup Relations Through Upregulated In-Group Empathy, Cooperation, Conformity, and Defense
abstract: Humans live in, rely on, and contribute to groups. Evolution may have biologically prepared them to quickly identify others as belonging to the in-group (vs. not), to decode emotional states, and to empathize with in-group members; to learn and conform to group norms and cultural practices; to extend and reciprocate trust and cooperation; and to aggressively protect the in-group against outside threat. We review evidence that these components of human group psychology rest on and are modulated by the hypothalamic neuropeptide oxytocin. It appears that oxytocin motivates and enables humans to 1) like and empathize with others in their groups, 2) comply with group norms and cultural practices, and 3) extend and reciprocate trust and cooperation, which may give rise to intergroup discrimination and sometimes defensive aggression against threatening (members of) out-groups. We explore the possibility that deficiencies in (components of) group psychology, seen in autistic spectrum disorder, schizophrenia, and borderline personality and social anxiety disorders, may be reduced by oxytocin administration. Avenues for new research are highlighted, and implications for the role of oxytocin in cooperation and competition within and between groups are discussed.

title: Oxytocin Enhances Amygdala-Dependent, Socially Reinforced Learning and Emotional Empathy in Humans
abstract: Oxytocin (OT) is becoming increasingly established as a prosocial neuropeptide in humans with therapeutic potential in treatment of social, cognitive, and mood disorders. However, the potential of OT as a general facilitator of human learning and empathy is unclear. The current double-blind experiments on healthy adult male volunteers investigated first whether treatment with intranasal OT enhanced learning performance on a feedback-guided item–category association task where either social (smiling and angry faces) or nonsocial (green and red lights) reinforcers were used, and second whether it increased either cognitive or emotional empathy measured by the Multifaceted Empathy Test. Further experiments investigated whether OT-sensitive behavioral components required a normal functional amygdala. Results in control groups showed that learning performance was improved when social rather than nonsocial reinforcement was used. Intranasal OT potentiated this social reinforcement advantage and greatly increased emotional, but not cognitive, empathy in response to both positive and negative valence stimuli. Interestingly, after OT treatment, emotional empathy responses in men were raised to levels similar to those found in untreated women. Two patients with selective bilateral damage to the amygdala (monozygotic twins with congenital Urbach–Wiethe disease) were impaired on both OT-sensitive aspects of these learning and empathy tasks, but performed normally on nonsocially reinforced learning and cognitive empathy. Overall these findings provide the first demonstration that OT can facilitate amygdala-dependent, socially reinforced learning and emotional empathy in men.

title: Methodological problems in the study of contagious yawning.
abstract: The recent interest in contagious yawning has raised several challenges as the varied methods of testing have left some unresolved issues. We do not know how differences in key variables affect the observed rates of yawning, and we highlight these as being in need of direct testing. Different researchers analyze their results differently, and we make some recommendations for more rigorous, thorough and informative analyses. Ultimately, problems arise when authors compare studies that used different methods and different analyses without acknowledging how these differences may have affected the results. In these cases, authors make inappropriate comparisons, which lead to conclusions that add confusion to the literature. Our goal in raising awareness of these issues is to generate new experiments and improve the discussion of existing research. With its link to empathy, a more standardized study of contagious yawning may be a useful tool for a variety of disciplines.

title: Are Yawns really Contagious? A Critique and Quantification of Yawn Contagion
abstract: Many diverse species yawn, suggesting ancient evolutionary roots. While yawning is widespread, the observation of contagious yawning is most often limited to apes and other mammals with sophisticated social cognition. This has led to speculation on the adaptive value of contagious yawning. Among this speculation are empirical and methodological assumptions demanding re-examination. In this paper we demonstrate that if yawns are not contagious, they may still appear to be so by way of a perceptual pattern-recognition error. Under a variety of conditions (including the assumption that yawns are contagious) we quantify (via models) the extent to which the empirical literature commits Type-1 error (i.e., incorrectly calling a spontaneous yawn ‘contagious’). We report the results of a pre-registered behavioural experiment to validate our model and support our criticisms. Finally, we quantify – based on a synthesis of behavioural and simulated data – how ‘contagious’ a yawn is by describing the size of the influence a ‘trigger’ yawn has on the likelihood of a consequent yawn. We conclude by raising a number of empirical and methodological concerns that aid in resolving higher-order questions regarding the nature of contagious yawning, and make public our model to help aid further study and understanding.

title: The Time Frame of Partner Choice in the Grooming Reciprocation of Cebus apella
abstract: Recent theoretical and experimental studies argued that reciprocity is constrained by the cognitive limitations of most animals and that, when reciprocation occurs, it should necessarily be short term. In this study, we examined the time frame of partner choice in the reciprocal grooming of captive female tufted capuchin monkeys (Cebus apella). Female capuchins groomed preferentially those individuals that overall groomed them most. Tufted capuchins did sometimes reciprocate grooming immediately. We quantified the time course and probability of immediate reciprocation, and excluded from the analysis cases of immediate reciprocation. We then showed that, even excluding immediate reciprocation, female capuchins still preferred to groom those individuals that groom them most. Our results show that partner choice is not necessarily based on immediate reciprocation and suggest that capuchins are able to reciprocate over longer time frames. These findings argue against the hypothesis that long-term reciprocation is absent in species lacking sophisticated cognitive abilities. We suggest that reciprocal altruism over long time frames relies on a system of emotional bookkeeping.

title: How dogs scan familiar and inverted faces: an eye movement study
abstract: AbstractFaces play an important role in communication and identity recognition in social animals. Domestic dogs often respond to human facial cues, but their face processing is weakly understood. In this study, facial inversion effect (deficits in face processing when the image is turned upside down) and responses to personal familiarity were tested using eye movement tracking. A total of 23 pet dogs and eight kennel dogs were compared to establish the effects of life experiences on their scanning behavior. All dogs preferred conspecific faces and showed great interest in the eye area, suggesting that they perceived images representing faces. Dogs fixated at the upright faces as long as the inverted faces, but the eye area of upright faces gathered longer total duration and greater relative fixation duration than the eye area of inverted stimuli, regardless of the species (dog or human) shown in the image. Personally, familiar faces and eyes attracted more fixations than the strange ones, suggesting that dogs are likely to recognize conspecific and human faces in photographs. The results imply that face scanning in dogs is guided not only by the physical properties of images, but also by semantic factors. In conclusion, in a free-viewing task, dogs seem to target their fixations at naturally salient and familiar items. Facial images were generally more attractive for pet dogs than kennel dogs, but living environment did not affect conspecific preference or inversion and familiarity responses, suggesting that the basic mechanisms of face processing in dogs could be hardwired or might develop under limited exposure.

title: Task‐Correlated Facial and Head Movements in Classifier‐Based Real‐Time fMRI
abstract: Real‐time fMRI is especially vulnerable to task‐correlated movement artifacts because statistical methods normally available in conventional analyses to remove such signals cannot be used in the context of real‐time fMRI. Multi‐voxel classifier‐based methods, although advantageous in many respects, are particularly sensitive. Here we systematically studied various movements of the head and face to determine to what extent these can “masquerade” as signal in multi‐voxel classifiers.

title: Characterization of autism spectrum disorder with spontaneous hemodynamic activity.
abstract: Functional near-infrared spectroscopy (fNIRS) was used to investigate spontaneous hemodynamic activity in the temporal cortex for typically developing (TD) children and children with autism spectrum disorder (ASD). Forty-seven children participated in the experiments including twenty-five with ASD. Compared with TD children, children with ASD showed weaker bilateral resting-state functional connectivity (RSFC), but much stronger fluctuation magnitude in terms of oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb). Differentiating between ASD and TD based on a support vector machine (SVM) model including bilateral RSFC and the fluctuation power of HbO2 and Hb as variables could achieve high accurate classification with sensitivity of 81.6% and specificity of 94.6%. This study demonstrates optical brain imaging has the potential for screening children with risk of ASD.