Mirror test

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The mirror test is a measure of self-awareness developed by Gordon Gallup Jr in 1970. ^[1]

The test gauges 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 an odourless dye, and observing whether the animal reacts in a manner consistent with it being aware that the dye is located on its own body. 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 finger while viewing the mirror.

Animals which have passed the mirror test are common chimpanzees, bonobos, orangutans, dolphins, elephants, humans and possibly pigeons. Surprisingly, gorillas have not passed the test, although at least one specific gorilla, Koko, has passed the test; this is probably because gorillas consider eye contact an aggressive gesture and normally try to avoid looking each other in the face. Human children tend to fail this test until they are at least 1.5 to 2 years old [1]. Dogs and 1 year old children, for example, usually react to a mirror in fear or curiosity, or simply ignore it, while birds often attack their own reflections.

Capuchin monkeys react in a way that indicates an intermediate state between seeing the mirror as another individual and recognizing the image as self.

There is some debate in the scientific community as to the value and interpretation of results of the mirror test. While this test has been extensively conducted on primates, there is also debate as to the value of the test as applied to animals who rely primarily on senses other than vision, such as dogs. As dogs have very poor visual resolution and acuity with red/green blindness, they have little chance of recognizing themselves or a dot (commonly red) in a mirror. However, dogs do recognize their own scent invariably with 40x more neurons than humans dedicated to processing smell. The key point being that the mirror test is only a measure of ability closely matching humans, not a statement of Consciousness, as is popularly believed. Additionally, as mentioned with gorillas, many animals may regard eye contact as a threatening gesture, so the application of the mirror test is unclear. Some mammalian species do not have stereoscopic vision, including rabbits and deer, which may be a factor in determining the value of the test.

In 1981, Epstein, Lanza and Skinner published a Science paper in which they argued that the pigeon also passes the mirror test, making it the only non-mammal to do so. However, the methodology of the experiment has been criticised for explicitly training the pigeons to perform the criterion response (i.e. pecking at the mark.) See pigeon intelligence.