The mirror test is a practice in psychology that has been used since the early 1970s to determine if an animal or young human child possesses a level of innate self-awareness when he or she sees his or her reflection in a mirror. The idea of using mirrors to gauge self-awareness is founded upon experiments conducted by Charles Darwin, when he used them to observe reactions in orangutans at zoos. For many decades, the mirror test was believed to reveal the fact that only higher primates had the ability to be self-aware on a fundamental level. Increasing use of the test over time, however, has revealed the presence of self-awareness in other species such as ocean-going mammals like dolphins and orcas, elephants, and the crow family of Corvidae birds including magpies.
The first conclusive evidence that magpies could pass the mirror test occurred in 2008 and put the practice of cognitive tests using mirrors in question as a reliable science. Previous assumptions about self-awareness being only present in certain primates was based on the fact that these species possessed a well-developed neocortex region of the brain. The neocortex is the largest region of the cerebral cortex of the brain in higher animals, and it is believed to be the region that most recently developed from an evolutionary viewpoint. The neocortex, which is the center of all higher brain functions, does not exist at all in the magpie.
The way in which the mirror test is conducted is open to some subjective interpretation, but it is generally considered to be reliable as statistical evidence over time has backed up its results. With animals, the subject is given a small, recognizable dot of dye on its body and, when a mirror is presented to the animal, if it detects the spot of dye and therefore recognizes the reflection in the mirror as being one of its own body, it will try to interact with the spot. The animal may demonstrate recognition of itself by trying to remove the dot of dye or searching for it on its body, where it was not able to see it otherwise without the aid of the mirror. An animal that fails the mirror test will react to its own reflection as if it is another animal with aggressive or fear-based responses.
In human children, the evidence in the past has suggested that infants were not able to recognize their reflection as being an image of themselves until at least the age of 18 months. It was believed up to the year 2010 that almost all human children were able to pass the mirror test as of age 24 months, but this has been proven to be a false bias based on the predominant testing of children in western nations. Children in some non-western nations such as Kenya and Fiji may fail to pass the test up to the age of 6 years, which has resulted in doubt as to the bias-free nature of the science itself. Only four primate species outside of humans consistently pass the mirror test as well, and species like Capuchin monkeys or other intelligent mammals like pigs universally fail it.
The mirror test tends to work in animals that have an inordinate amount of concern for their appearance such as magpies, and works less well in others. For example, though elephants pass the mirror test and are commonly accepted as self-aware creatures, research in 2006 revealed that only one out of three elephants passed the test. This is believed to be because the elephants have little motivation or concern for investigating odd marks that are placed on their skin and which can only be examined and manipulated by looking at their image in a mirror. The same flaw may exist in the temperament of most dogs, who seem to recognize themselves in mirrors but have little desire to examine spots placed upon their bodies. Gorillas are one of the most successful primates that pass the mirror test, and part of the reason for this is believed to be the gorilla's highly social behavior, ranking among groups by eye contact and physical appearance which makes them overly concerned with noticeable changes.