Affective Empathy: Exploring Prosocial Behavior in Neuroscience

Empathy is an emotion that often instigates prosocial actions, so research increasingly focuses on the biological basis of this quality. Because affective empathy develops before the components of cognitive regulation, lower order mammalian species should be able to express empathy from an affective perspective. A rat model of empathy has been developed, showing that a free rat in an arena with a restrained conspecific will act prosocially and open the door of the restrainer. This study explores affective isomorphy as a criterion of affective empathy, by placing the free rats in the restrainer prior to being the free rat in the testing arena. The control condition rats did not experience the previous restraint. Number of door openings and latency to door openings were measured in 60 minute testing sessions. No significant effect of condition was found for number of door openings or latency to door openings. We conclude that affective isomorphy may not strengthen empathetic behaviors. Introduction Defining the abstract quality of empathy in the concrete world of research plagues the scientific community. Researchers have extensively investigated the fundamental mechanisms of how humankind operates and functions through animal models, but higher order cognitive functions, such as emotions and sentient feelings, are far more complicated to study. However, these studies are critical to our understanding of the human condition. People vary greatly in their empathetic abilities. Individuals with Running head: EMPATHY: AFFECTIVE EMPATHY IN A RAT MODEL 3 autism or psychopathy may not be able to express empathy, whereas social workers or doctors may have incredible empathetic skills. Empathy is an emotion that often instigates prosocial actions, so research increasingly focuses on the biological basis of this quality. However, before empathy can be studied concretely, researchers must come to a general consensus on an operational definition. Coming up with an operational definition has posed a challenge, and the definition of empathy is often debated among researchers, complicating the formulation of scientific research exploring the neural basis and exploration of this abstract behavior. The simple definition of empathy is “the ability to share another’s internal world of thoughts and feelings (Walter, 2012). ” Empathy has further been defined as a cognitive trait, the ability to comprehend the emotions of another, as well as an affective trait, the ability to experience the emotional state of another (Jolliffe & Farrington, 2006; Geng, Xia, & Qin, 2012), though some people propose that the quality requires both cognitive and affect traits as well as a regulatory mechanism (Decety & Jackson, 2004). Cognitive neuroscientists tend to focus on the affective component of empathy. Their definition focuses on an affective reaction to the affective state of someone else (Singer & Lamm, 2009). Walter (2012) clarifies affective empathy by the distinct qualifications of affective behavior, affective experience, affective isomorphy, perspective, distinction between the other and the self, and knowledge of causal relation between the differences in affective states of individuals. To use this model of empathy the individual must experience a feeling or state that is caused by the inferred state of Running head: EMPATHY: AFFECTIVE EMPATHY IN A RAT MODEL 4 another. This feeling or state must be similar to something experienced before so that some cognitive appreciation can be identified between the self and the other. Because empathetic behavior requires the ability to infer the state of the other, many believe empathy to be only a human quality or behavior, claiming that it requires higher cognitive processing abilities (Walter, 2012). Empathy requires a sharing of experience, recognition of another’s pain which often (but not always) leads toward a goal-oriented action to help. The human brain has complex neural networks that facilitate these empathetic actions. The middle anterior cingulate cortex (mACC) and anterior insula are referred to as the shared pain network, and have been hypothesized to serve as a bridge between an observer and a victim (Bruneau, Pluta, & Saxe, 2012). The theory o f the mind network, including the temporo-parietal junction, precuneus, and medial prefrontal cortex, have been significantly linked to identifying and thinking about the emotional experience of another, and only in humans (Walter, 2012). However, empathy is not specific to the human species, and much of the biological mechanisms are shared with other mammals (Decety, 2011). The theory o f the mind network has not been studied in mammals. While human empathy studies utilize top-down processing (cognitive empathy), the link between human empathy and mammalian empathy can best be understood by looking from bottom-up perspectives (affective empathy), especially if these are tangible shared networks ( Cromwell & Panksepp, 2011). Science allows us to explore phenomena from multiple directions. In this case, the exploration of empathy does not always have to start from a cellular or structural Running head: EMPATHY: AFFECTIVE EMPATHY IN A RAT MODEL 5 basis, and researchers have uncovered vast amounts of knowledge from behavioral observations. What could research uncover by studying empathy from a behavioral perspective rather than from a neural mechanistic prospective, evaluating the shared mechanisms of behavior? The ultimate goal of empathy research requires approaching the questions from a variety of methodologies. Perhaps the direction of studying this quality should begin at behavioral observations, and then specify toward neural mechanisms. Measures of empathy in humans are most commonly self-report questionnaires (Gerdes, Lietz, & Segal, 2011). These include measures of both cognitive empathy, the Hogan Empathy Scale as one example (Hogan, 1969), and affective empathy, the Questionnaire Measure of Emotional Empathy (Mehrabian & Epstein, 1972) as another. Affective empathy develops before the cognitive and regulation components, using bottom-up involuntary somato-sensorimotor processes (Decety, 2011). Therefore, if affective empathy is a bottom-up process in the brain, lower order mammalian species should be able to express empathy in an affective perspective. Studies of the primate brain indicate their empathetic capabilities (Palagi, Leone, Mancini, & Ferrari, 2009; Campbell & de Waal, 2011; de Waal, 2012), and elephant cognition allude to empathetic behaviors as well (Byrne, Bates, & Moss, 2009). One of the preliminary studies of empathy in rodents used a measure of leverpressing task paired with a shock pain of a conspecific rat to evaluate the rat’s reaction to the conspecific’s pain (Church, 1959). Conditioned rats decreased lever pressing to reduce the shock inflicted on the conspecific rat, indicating the understanding of a Running head: EMPATHY: AFFECTIVE EMPATHY IN A RAT MODEL 6 difference between its previous experience of pain and the shocked rat. Other studies demonstrate the ability of rodents to reduce the distress of other rats in a suspended condition (Rice & Gainer, 1962) or noxious olfactory stimulus (Langford et al., 2006). These studies have not claimed rats to be empathetic, but rather they explored basic elements of what researchers would consider affective empathetic behavior. A newer and more specific rat model of empathy has been developed and does support empathetic behavior in rats. Freely moving rats will use physical effort to open a restrainer, freeing another restrained rat (Bartal, Decety, & Mason, 2011). This behavior shows the rat’s ability to respond to the affective state of another, expressing empathy. The free rats identified the trapped rats’ distress and down regulated their own fear in order to exhibit a pro-social behavior. All this combined with the ability to recognize their own freedom compared to the conspecific rats’ restraint qualifies this action as an empathetic motivated behavior in a rat model. However, according to Walter’s conditions of empathy, the free rat had never experienced the defining criterion of affective isomorphy, in this case, the same state of having once been restrained. The requirement of affective isomorphy as a criterion of empathy may not be so much as a requirement, but rather it provides an empirical tool in the evaluation of neural mechanisms (Walter, 2012). Can affective isomorphy teach us more about empathy in behavioral research? This study of empathy in rat models will be designed such that the free rat will be conditioned by being placed in the restrainer (condition restrainedCR) before being placed in the arena as the free rat. This will be our condition of affective isomorphy. It Running head: EMPATHY: AFFECTIVE EMPATHY IN A RAT MODEL 7 will then have the opportunity to let its cagemate out of the restrainer. We will evaluate if the CR conditioned rat, having been in the same state before, will open the restrainer at a shorter latency than a rat in the control group, naive to the restrainer (testing restrainedTR). This will evaluate whether affective isomorphy as a criterion of empathy is necessary to elicit a pro-social, empathetic behavior. We hypothesize that the rats that had been in the restrainer will open the restrainer at a shorter latency than rats that previously had not been in that state, and will show significantly more door openings than the TR group. Method Subjects Eight pairs of female Sprague-Dawley rats were housed in the Regis University Department of Psychology and Neuroscience’s animal facility with a cagemate for two weeks prior to testing. Rats were weighed daily during testing. A color-mark on each rat’s tail distinguished cagemates. Rat Selection In order to select one of the cagemates to be the free rat and the other to be the restrained rat, the boldness of the rats was evaluated. For each pair, boldness was measured by an approach