Mirror test

The mirror test—sometimes called the mark test, mirror self-recognition (MSR) test, red spot technique, or rouge test—is a behavioral technique developed in 1970 by American psychologist Gordon Gallup Jr. to determine whether an animal possesses the ability of visual self-recognition. In this test, an animal is anesthetized and then marked (e.g. paint or sticker) on an area of the body the animal normally cannot see (e.g. forehead). When the animal recovers from the anesthetic, it is given access to a mirror. If the animal then touches or investigates the mark on itself, it is taken as an indication that the animal perceives the reflected image as an image of itself, rather than of another animal.
The MSR test became the traditional method for measuring physiological and cognitive self-awareness. Very few species passed it. However, several critiques have emerged that call into question the value of Gallup's test. Studies have challenged Gallup's results; others have found that animals can be self-aware in ways not measured by the test, such as distinguishing between their own and others' songs and scents.
The inspiration for the mirror test comes from an anecdote about Charles Darwin and a captive orangutan. While visiting the London Zoo in 1838, Darwin observed an orangutan named Jenny throwing a tantrum after being teased with an apple by her keeper. This started him thinking about the subjective experience of an orangutan. He also watched Jenny gaze into a mirror and noted the possibility that she recognized herself in the reflection.
In 1970, Gordon Gallup Jr. experimentally investigated the possibility of self-recognition with two male and two female wild preadolescent chimpanzees (Pan troglodytes), none of which had presumably seen a mirror previously. Each chimpanzee was put into a room by itself for two days. Next, a full-length mirror was placed in the room for a total of 80 hours at periodically decreasing distances. A multitude of behaviors was recorded upon introducing the mirrors to the chimpanzees. Initially, the chimpanzees made threatening gestures at their images, ostensibly seeing their reflections as threatening. Eventually, the chimps used their reflections for self-directed responding behaviors, such as grooming parts of their body previously not observed without a mirror, picking their noses, making faces, and blowing bubbles at their reflections.
Gallup expanded the study by manipulating the chimpanzees' appearance and observing their reaction to their reflection in the mirror. Gallup anesthetized the chimps and then painted a red alcohol-soluble dye on the eyebrow ridge and the top half of the opposite ear. When the dye dried, it had virtually no olfactory or tactile cues. Gallup then removed the mirror before returning the chimpanzees to the cage. After regaining full consciousness, he recorded the frequency with which the chimps spontaneously touched the marked areas of skin. After 30 minutes, the mirror was reintroduced into the cage, and the frequency of touching the marked areas was again determined. With the mirror present, the frequency increased from four to ten, compared to only one when the mirror had been removed. The chimpanzees sometimes visually or olfactorily inspected their fingers after touching the marks. Other mark-directed behavior included turning and adjusting the body to better view the mark in the mirror or tactile examination of the mark with an appendage while viewing the mirror.
An essential aspect of the classical mark test (or rouge test) is that the mark/dye is nontactile, preventing attention from being drawn to the marking through additional perceptual cues (somesthesis). For this reason, animals in the majority of classical tests are anesthetized. Some tests use a tactile marker. If the creature stares unusually long at the part of its body with the mark or tries to rub it off, then it is said to pass the test.
Animals that are considered to be able to recognize themselves in a mirror typically progress through four stages of behavior when facing a mirror:
Gallup conducted a follow-up study in which two chimps with no prior experience with a mirror were put under anesthesia, marked, and observed. After recovery, they made no mark-directed behaviors before or after being provided with a mirror.
The rouge test was also done by Michael Lewis and Jeanne Brooks-Gunn in 1979 for the purpose of self-recognition with human mothers and their children.
The default implication drawn from Gallup's test is that those animals who pass the test possess some form of self-recognition. However, a number of authors have suggested alternative explanations of a pass. For example, Povinelli suggests that the animal may see the reflection as some odd entity that it is able to control through its own movements. When the reflected entity has a mark on it, then the animal can remove the mark or alert the reflected entity to it using its own movements to do so. Critically, this explanation does not assume that the animals necessarily see the reflected entity as "self".
The MSR test has been criticized for several reasons, in particular because it may result in false negative findings.
It may be of limited value when applied to species that primarily use senses other than vision. Humans have been determined by biologists to have some of the best eyesight amongst animals, exceeding the overwhelming majority in daylight settings, though a few species have better. By contrast, dogs for example mainly use smell and hearing; vision is used third. This may be why dogs fail the MSR test. With this in mind, biologist Marc Bekoff developed a scent-based paradigm using dog urine to test self-recognition in canines. He tested his own dog, but his results were inconclusive. Dog cognition researcher Alexandra Horowitz formalized Bekoff's idea in a controlled experiment, first reported in 2016 and published in 2017. She compared the dogs' behavior when examining their own and others' odors, and also when examining their own odor with an added smell "mark" analogous to the visual mark in MSR tests. These subjects not only discriminated their own odor from that of other dogs, as Bekoff had found, but also spent more time investigating their own odor "image" when it was modified, as subjects who pass the MSR test do. A 2016 study suggested an ethological approach, the "Sniff test of self-recognition (STSR)" which did not shed light on different ways of checking for self-recognition. Dogs also show self-awareness in the size and movement of their bodies. Garter snakes, a relatively social snake species, have also passed an odor based "mirror" test.
Another concern with the MSR test is that some species quickly respond aggressively to their mirror reflection as if it were a threatening conspecific, thereby preventing the animal from calmly considering what the reflection actually represents. This may be why monkeys fail the MSR test.
In an MSR test, animals may not recognise the mark as abnormal, or may not be sufficiently motivated to react to it. However, this does not mean they are unable to recognize themselves. For example, in an MSR test conducted on three elephants, only one elephant passed the test, but the two elephants that failed still demonstrated behaviors that can be interpreted as self-recognition. The researchers commented that the elephants might not have touched the mark because it was not important enough to them. Similarly, lesser apes infrequently engage in self-grooming, which may explain their failure to touch a mark on their heads in the mirror test. In response to the question of the subject's motivation to clean, another study modified the test by introducing child subjects to a doll with a rouge spot under its eye and asking the child to help clean the doll. After establishing that the mark was abnormal and to be cleaned, the doll was put away and the test continued. This modification increased the number of self-recognisers.
Frans de Waal, a biologist and primatologist at Emory University, has stated that self-awareness is not binary, and the mirror test should not be relied upon as a sole indicator of self-awareness, though it is a good test to have. Different animals adapt to the mirror in different ways.
Several studies using a wide range of species have investigated the occurrence of spontaneous, mark-directed behavior when given a mirror, as originally proposed by Gallup. Most marked animals given a mirror initially respond with social behavior, such as aggressive displays, and continue to do so during repeated testing. Only a few species have touched or directed behavior toward the mark, thereby passing the classic MSR test.
Findings in MSR studies are not always conclusive. Even in chimpanzees, the species most studied and with the most convincing findings, clear-cut evidence of self-recognition is not obtained in all individuals tested. Prevalence is about 75% in young adults and considerably less in young and aging individuals.
Until the 2008 study on magpies, self-recognition was thought to reside in the neocortex area of the brain. However, this brain region is absent in nonmammals. Self-recognition may be a case of convergent evolution, where similar evolutionary pressures result in similar behaviors or traits, although species arrive at them by different routes, and the underlying mechanism may be different.
Cephalopods
Some animals that have reportedly failed the classic MSR test include:
Gibbon (g. Hylobates, Symphalangus and Nomascus) have failed to show self-recognition in at least two tests. However, modified mirror tests with three species of gibbons (Hylobates syndactylus, H. gabriellae, H. leucogenys) in 2000 showed convincing evidence of self-recognition even though the animals failed the standard version of the mirror test. Another study published in 2009 documents 12 cases of spontaneous self-recognition in front of the mirror by a pair of siamangs (Symphalangus syndactylus). Capuchin monkey (Cebus apella) did not pass in one test but recognized the reflection as special in another.
Rhesus macaque (Macaca mulatta) Though macaques failed the original mark test, they have been reported to exhibit other behaviours that indicate self-recognition. Rhesus macaques have been observed to use mirrors to study otherwise-hidden parts of their bodies, such as their genitals and implants in their heads. It has been suggested this demonstrates at least a partial self-awareness, although further study is needed.
Pigs can use visual information seen in a mirror to find food. In a 2009 experiment, seven of the eight pigs who spent 5 hours with a mirror were able to find a bowl of food hidden behind a wall and revealed using a mirror. Pigs that had no experience with mirrors, looked behind the mirror for the food. BBC Earth also showed the food bowl test, and the "matching shapes to holes" test, in the Extraordinary Animals series.
There is evidence of self-recognition when presented with their reflections. So far, pigs have not been observed to pass the mirror mark test, however.
Adelie penguins do not react as if they would react to a wild bird, and when presented with a mirror, gestured as if they recognized themselves. However, they were not bothered enough by marks on their face to notice.
Two captive giant manta rays showed frequent, unusual and repetitive movements in front of a mirror, suggesting contingency checking. They also showed unusual self-directed behaviors when exposed to the mirror. Manta rays have the largest brains of all fish. In 2016, Csilla Ari tested captive manta rays at the Atlantis Aquarium in the Bahamas by exposing them to a mirror. The manta rays appeared to be extremely interested in the mirror. They behaved strangely in front the mirror, including doing flips and moving their fins. They also blew bubbles. They did not interact with the reflection as if it were another manta ray; they did not try to socialize with it. However, only an actual mirror test can determine if they actually recognize their own reflections, or if they are just demonstrating exploratory behavior. A classic mirror test has yet to be done on manta rays.
Another fish that may pass the mirror test is the common archerfish, Toxotes chatareus. A study in 2016 showed that archerfish can discriminate between human faces. Researchers showed this by testing the archerfish, which spit a stream of water at an image of a face when they recognized it. The archerfish would be trained to expect food when it spat at a certain image. When the archerfish was shown images of other human faces, the fish did not spit. They only spit for the image that they recognized. Archerfish normally, in the wild, use their spitting streams to knock down prey from above into the water below. The study showed that archerfish could be trained to recognize a three-dimensional image of one face compared to an image of a different face and would spit at the face when they recognized it. The archerfish were even able to continue recognizing the image of the face even when it was rotated 30, 60 and 90°.
The rouge test is a version of the mirror test used with human children. Using rouge makeup, an experimenter surreptitiously places a dot on the face of the child. The children are then placed in front of a mirror and their reactions are monitored; depending on the child's development, distinct categories of responses are demonstrated. This test is widely cited as the primary measure for mirror self-recognition in human children.
There is criticism that passing a rouge test may be culturally motivated, and that what is commonly thought about mirror self-recognition actually applies only to children of Western countries. A study from 2010 tested children from rural communities in Kenya, Fiji, Saint Lucia, Grenada and Peru, as well as urban United States and rural Canada. The majority of children from the US and Canada passed the MSR test, but fewer children from the other regions passed the MSR test. In the Kenya test, only 3% of children aged 18–72 months touched the mark. In the Fiji test, none of the children aged 36–55 months touched the mark. The other non-Western rural children scored much better, but still markedly worse than their Western counterparts.
In a study in 1972, from the ages of 6 to 12 months, children typically saw a "sociable playmate" in the mirror's reflection. Self-admiring and embarrassment usually began at 12 months, and at 14 to 20 months, most children demonstrated avoidance behaviors. By 20 to 24 months, self-recognition climbed to 65%. Children did so by evincing mark-directed behavior; they touched their own noses or tried to wipe the marks off. In another study, in 1974, at 18 months, half of children recognized the reflection in the mirror as their own.
Self-recognition in mirrors apparently is independent of familiarity with reflecting surfaces. In some cases, the rouge test has been shown to have differing results, depending on sociocultural orientation. For example, a Cameroonian Nso sample of infants 18 to 20 months of age had an extremely low amount of self-recognition outcomes at 3.2%. The study also found two strong predictors of self-recognition: object stimulation (maternal effort of attracting the attention of the infant to an object either person touched) and mutual eye contact. A strong correlation between self-concept and object permanence have also been demonstrated using the rouge test.
The rouge test is a measure of self-concept; the child who touches the rouge on their own nose upon looking into a mirror demonstrates the basic ability to understand self-awareness. Animals, young children, and people who have gained sight after being blind from birth, sometimes react to their reflection in the mirror as though it were another individual.
Theorists have remarked on the significance of this period in a child's life. For example, psychoanalyst Jacques Lacan used a similar test in marking the mirror stage when growing up. Current views of the self in psychology position the self as playing an integral part in human motivation, cognition, affect, and social identity.
In 2012, early steps were taken to make a robot pass the mirror test.