Animals May Fail Self-Awareness Tests Only Because They Don’t Understand Mirrors

Scientists from the Shanghai Institutes for Biological Sciences have found that if monkeys learn how mirrors work, they can pass self-awareness tests. This provides evidence for the increasingly popular theory that most animals fail these tests only because they don’t understand mirrors. The results of the study are in a paper that was just published in the journal Proceedings of the National Academy of Sciences.

Self-awareness is generally considered to be an ability that is unique to humans and a few of our closest relatives, the great apes. The most popular test for studying self-awareness in animals is called mirror self-recognition (MSR). In MSR tests, the animal is placed in front of a mirror after the researchers have secretly painted a mark on the animal’s face with colored dye. If the animal touches or tries to remove the mark, the research team will declare that the individual is capable of self-awareness. However, many researchers are now arguing that species that fail the test may simply be confused by the mirror itself. If an animal doesn’t understand how a mirror works, they’re unlikely to pass.

Rhesus monkeys (Macaca mulatta) tend to pass intelligence tests but not the MSR, prompting researchers to test the theory that they may not know how mirrors work. The team first taught the monkeys by rewarding them for touching the correct spots on a board when the dots were only visible on a nearby mirror. After a few weeks, the researchers began placing the laser dots on the monkeys so that the animals would fully understand how the mirrors worked. After this training, all of the monkeys passed the MSR test. In fact, the animals began to look at body parts they couldn’t normally see, a major indicator of self-awareness.

The team’s findings show that current MSR methods may not be a good test of self-awareness without first training the animals to use mirrors. The researchers emphasize the need to retest intelligent animals that had previously failed MSR.


Chang et al. Spontaneous expression of mirror self-recognition in monkeys after learning precise visual-proprioceptive association for mirror images. Proceedings of the National Academy of Sciences (2017).

You Might Like –



Plant Science