The
mirror test is a measure of
self-awarenessSelf-awareness is literally consciousness of one's self. It is related to but not identical with self-consciousness-A philosophical view:I think, therefore I am...
developed by
Gordon Gallup Jr.Gordon G. Gallup, Jr. is a psychologist currently working at the University at Albany's Psychology department in the biopsychology program area. He received his Ph.D. from Washington State University in 1968, after which he joined the faculty of the Psychology Department at Tulane University...
in 1970, that was based in part on observations made by
Charles DarwinCharles Robert Darwin FRS was an English naturalist who realised and presented compelling evidence that all species of life have evolved over time from common ancestors, through the process he called natural selection...
. While visiting a zoo, Darwin held a mirror up to an orangutan and recorded the animal's reaction, which included making a series of facial expressions. Darwin noted that the significance of these expressions was ambiguous, and could either signify that the primate was making expressions at what it perceived to be another animal, or it could be playing a sort of game with a new toy.
The
mirror test is a measure of
self-awarenessSelf-awareness is literally consciousness of one's self. It is related to but not identical with self-consciousness-A philosophical view:I think, therefore I am...
developed by
Gordon Gallup Jr.Gordon G. Gallup, Jr. is a psychologist currently working at the University at Albany's Psychology department in the biopsychology program area. He received his Ph.D. from Washington State University in 1968, after which he joined the faculty of the Psychology Department at Tulane University...
in 1970, that was based in part on observations made by
Charles DarwinCharles Robert Darwin FRS was an English naturalist who realised and presented compelling evidence that all species of life have evolved over time from common ancestors, through the process he called natural selection...
. While visiting a zoo, Darwin held a mirror up to an orangutan and recorded the animal's reaction, which included making a series of facial expressions. Darwin noted that the significance of these expressions was ambiguous, and could either signify that the primate was making expressions at what it perceived to be another animal, or it could be playing a sort of game with a new toy. There are nine species that pass the mirror test, including
magpieMagpies are passerine birds of the crow family, Corvidae. The names 'jay' and 'magpie' are to an extent interchangeable, although this does not accurately reflect the evolutionary relationship between these birds...
s and
elephantElephants are large land mammals in two genera of the family Elephantidae: Elephas and Loxodonta. Three species of elephant are living today: the African Bush Elephant, the African Forest Elephant and the Asian Elephant...
s but mostly primates. Most human babies do not pass the mirror test until several months of age.
Gordon Gallup built on these observations by devising a test that attempts to gauge self-awareness by determining whether an animal can recognize its own reflection in a mirror as an image of itself. This is accomplished by surreptitiously marking the animal with two odourless dye spots. The test spot is on a part of the animal that would be visible in front of a mirror, while the control spot is in an accessible but hidden part of the animal's body. Scientists observe if the animal reacts in a manner consistent with it being aware that the test dye is located on its own body while ignoring the control dye. Such behaviour might include turning and adjusting of the body in order to better view the marking in the mirror, or poking at the marking on its own body with a limb while viewing the mirror.
At first, even animals that are capable of passing the mirror test respond as the orangutan described by Darwin. In fact, young children and people who have been blind from birth but have their sight restored initially react as if their reflection in the mirror was another person.
Animals that pass the mirror test
Animals that have passed the mirror test are all of the great apes (
bonoboThe Bonobo , Pan paniscus, until recently called the Pygmy Chimpanzee and less often, the Dwarf or Gracile Chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the Common Chimpanzee...
s,
chimpanzeeChimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s,
orangutanThe orangutans are two endangered species of great apes. Known for their intelligence, they live in trees and are the largest living arboreal animal. They have longer arms than other great apes, and their hair is typically reddish-brown, instead of the brown or black hair typical of other great apes...
s,
gorillaGorillas are the largest of the living primates. They are ground-dwelling and predominantly herbivorous. They inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
s and humans),
bottlenose dolphinBottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the Common Bottlenose Dolphin and the Indo-Pacific Bottlenose Dolphin , where previous...
s,
OrcaThe Killer Whale or Orca , or less commonly, Blackfish, is the largest species of the dolphin family. Most people think that they are whales, but they are actually dolphins. They are called killer whales often because they sometimes hunt whales for food...
s, elephants, and
European MagpieThe European Magpie or Common Magpie is a resident breeding bird throughout Europe, much of Asia, and northwest Africa. It is one of several birds in the crow family named as magpies, and belongs to the Holarctic radiation of "monochrome" magpies.In Europe, "Magpie" is used by English speakers as...
s. Initially, it was thought that gorillas did not pass the test, but there are now several well-documented reports (such as one gorilla,
KokoKoko is a lowland gorilla who, according to Francine 'Penny' Patterson, is able to understand more than 1,000 signs based on American Sign Language, and understand approximately 2,000 words of spoken English...
) of gorillas passing the test. In 1981, Epstein, Lanza and
SkinnerBurrhus Frederic Skinner was an American psychologist, author, inventor, advocate for social reform, and poet. He was the Edgar Pierce Professor of Psychology at Harvard University from 1958 until his retirement in 1974...
published a paper in the journal
Science in which they argued that the pigeon also passes the mirror test. Pigeons though could only detect the spots on their own body after they had been trained to and untrained pigeons have never been able to pass the mirror test. However, magpies have been shown to pass the test by trying to remove a coloured sticker from underneath their beaks when shown it in a mirror. Humans tend to fail the mirror test until they are about 18 months old, or the "
mirror stageThe mirror stage was the subject of Jacques Lacan's first official contribution to psychoanalytic theory He described it in "The Mirror Stage as formative of the function of the I as revealed in psychoanalytic experience", the first of his Écrits. In the early 1950s, he no longer considered it as...
". Dogs, cats, and young human children all fail the mirror test.
Capuchin monkeyThe capuchins are the group of New World monkeys classified as genus Cebus. The range of the capuchin monkeys includes Central America and South America as far south as northern Argentina...
s react to their reflection either with hostility or affection, although mark test experiments have shown that they are incapable of spontaneous mirror self-recognition. Similar tests performed using video technology support these findings, but suggest that the monkeys possess the raw input systems required for explicit self-recognition.
Criticism of the mirror test
There is some debate as to the value and interpretation of results of the mirror test. While this test has been extensively conducted on primates, there is debate as to the value of the test as applied to animals who rely primarily on senses other than vision. Adaptations of the mirror test have been made in other modalities, such as scent. For instance, biologist Marc Bekoff developed a paradigm using dog urine for testing self-awareness in canines.
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