Research on the ability of animals to recognize themselves in mirrors began in the 1970s, and to date, only a few have passed the test.
Humans are the only species that gaze at their reflection in the mirror every day, but they are not the only ones that can recognize themselves on reflective surfaces. Scientists have studied self-recognition in many species, starting with the research on chimpanzees (Pan troglodytes) published in 1970.
A monkey looking in the mirror at a temple in Jaipur, India. (Photo: Ayse Topbas).
Animals ranging from ants, stingrays to African gray parrots (Psittacus erithacus) have been thoroughly studied for signs indicating they may have self-awareness when looking in the mirror. A few have shown they recognize they are observing themselves, many species do not recognize their reflection at all, while some exhibit ambiguous behaviors.
“Many animals do not pass the test. They need to spontaneously check a visual mark on their bodies in front of the mirror without any training or rewards. This action has to be spontaneous,” explained Frans de Waal, a primatologist at Emory University.
In the 1970 experiment, four chimpanzees were anesthetized, and red dye was marked on their faces. When they woke up, the chimpanzees examined the marked areas in the mirror, proving they understood they were looking at themselves. The mark test is considered the most convincing evidence of self-awareness in front of a mirror.
Many other great ape species also passed the test. Orangutans recognized themselves, even identifying the marks on their bodies, in a study conducted in 1973. A 1994 study showed that bonobos checked body areas that they would not be able to see without the mirror. However, experiments with gorillas did not yield clear results.
Monkeys often regard their reflection as another animal, although a series of controversial studies suggest that some monkey species can recognize themselves after undergoing training. Critics argue that such learned behavior is not reliable evidence of self-awareness.
An Asian elephant (Elephas maximus) passed the mirror test according to a 2006 study. (Photo: Chuchart Duangdaw).
Beyond great apes, until last year, the only land mammal that convincingly passed the test was an Asian elephant (Elephas maximus) at the Bronx Zoo in the United States. However, a study published in the journal Neuron in January 2024 suggests that mice may also recognize changes on their bodies in the mirror.
Dolphins may also be aware of their own reflections. A 1995 study using video instead of a mirror and a 2001 study using mirrors both indicated that dolphins rely on their images to check for marks on their bodies.
In 2008, a team of scientists studying Eurasian magpies (Pica pica) found the first evidence that a non-mammal species can recognize itself in a mirror. In 2022, wild Adélie penguins (Pygoscelis adeliae) also exhibited signs of self-awareness in front of a mirror, although they did not respond to colorful bibs placed around their necks for marking.
Testing on lower animals has sparked much debate. According to a 2015 study, ants may possess some degree of self-awareness because they attempt to remove a blue paint layer on their heads when looking at their reflection. Two studies in 2016 and 2019 showed that cleaner wrasses and Labroides dimidiatus could also recognize themselves in the mirror. In a 2024 study, a team of experts found that mice also sought to remove marks on their bodies.
Thus, organisms considered more primitive have passed the mirror test, while some of the most intelligent animals, excluding humans, including African gray parrots, have failed. This raises questions about the usefulness of the mirror test. Scientists are uncertain whether this test truly reflects animals’ self-awareness akin to humans or merely a form of bodily recognition.
