The mirror test
is a measure of self-awareness
developed by Gordon Gallup Jr.
in 1970. 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 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
whether 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.
Animals which pass the mirror test
Animals that have passed the mirror test are all of the great apes (bonobos, chimpanzees, orangutans and gorillas), bottlenose dolphins, killer whales, elephants, and European Magpies. Initially, it was thought that gorillas do not pass the test, but there are now several well-documented reports (such as one gorilla, Koko ) of gorillas passing the test. In 1981, Epstein, Lanza and Skinner published a paper in the journal Science in which they argued that the pigeon also passes the mirror test. Humans tend to fail this test until they are about 18 months old, or the "mirror stage". Dogs, cats 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 to their reflection either with hostility or affection but there is no conclusive evidence that they recognize themselves in the mirror as opposed to believing their reflection is another capuchin monkey.
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 color 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
, which may be a factor in determining the value of the test.