The standard test of self-awareness is being able to recognize ourselves in a mirror. Although chimpanzees pass this test with flying colors, gorillas have inconsistent results. Dogs flunk by treating the reflection as another animal.

Experimentally Self-Aware Animals

Gordon Gallup (1) devised the first credible test for self-awareness. He exposed chimps to a large mirror so that they could get familiar with their own image. A dye mark was surreptitiously placed on the brows of mirror-exposed chimpanzees. The chimps behaved very much as humans might under similar circumstances. They used the mirror to inspect the mark, touched it with a finger, and attempted to remove it.

Few animals pass the mirror test for self-awareness (appropriately modified for species differences in anatomy). They include chimpanzees, bonobos (pygmy chimpanzees), orangutans, at least one elephant (Happy, Plotnik, 2006), dolphins, humpback whales, and magpies (3). Apart from the magpies, all of these are large-brained animals. They are all highly social as well, with the exception of orangutans, which are mostly solitary as adults.

Magpies are the big surprise on this list, but they and their relatives (the corvids, or crows) are intelligent and pass problem-solving tests that only great apes can master. Results are mixed for gorillas and capuchin monkeys, with some studies reporting that they pass the mirror test but others reporting that they fail.

Surprisingly, dogs do not pass the self-awareness test. Dogs are highly intelligent, extremely social, and fit right in with human households, even to the extent of voluntarily learning to recognize the meaning of human words.

Anyone who saw the 60 Minutes segment on border collies knows that these clever dogs are extremely attentive to the needs of their masters. One collie had a large collection of about a thousand stuffed toys that he could retrieve on demand. “Fetch Kermit” always yielded the frog from Sesame Street, for instance, and whichever toy was requested, the dog retrieved it. It is hard to imagine that this is anything but intelligent behavior (as opposed to operant conditioning). If so, it suggests that the dog has a clear grasp of the owner's intentions, hinting that a capacity for self-awareness is not unthinkable.

Why Gorillas and Dogs Fail

Inconsistent results for gorillas in mirror self-recognition are sometimes attributed to their relatively small brain size relative to chimpanzees. Yet this is a shaky argument. They demonstrate interest in painting captive animals (4), and male gorillas sometimes care for orphans—something that is unknown in chimpanzees (5). This behavior could be motivated by empathy that suggests self-awareness, although other interpretations are possible.

Gorillas may do poorly at the mirror test because they avoid looking directly at strangers, as this constitutes a threat display. So it is hard for them to learn that the mirror reflection is themselves.

Dog lovers complain that the mirror test favors visual animals like primates but makes it difficult for dogs, which are more focused on auditory and olfactory cues.

Correlates of Self-Awareness in Dogs

In addition to their general intelligence, as reflected in the many useful tasks that dogs perform for humans (rescuing skiers, herding sheep, silently pointing to prey animals), dogs are socially astute. An ostensibly well-behaved animal might grab a piece of meat from a countertop as soon as its owner's back is turned. If caught in the act, the dog cringes in a way that suggests guilt, or at least fear of punishment. It is difficult to understand these actions without assuming the animal has some sort of mental representation of how it is expected to behave.

Animal cognition researcher Marc Bekoff (6) found his dog Jethro (a neutered Rottweiler mix) could recognize his own scent marks from urine in snow and avoided marking over them, but that is not exactly self-awareness. Indeed, it is likely that all scent-marking animals avoid marking over their own scent in a reflexive way. Better controlled tests replicated Bekoff's result that dogs spend less time sniffing their own scent.

Much as we might wish to believe that man's best friend is self-aware, there is no good supportive evidence as yet, although this may reflect problems with the tests. At this point, all we can claim is that domestic dogs are almost incredibly well attuned to the niche of serving humans. They may have accomplished this so well that we are fooled into thinking they have much the same inner life as we do.


1 Gallup, G. E. (1970). Self-awareness in the chimpanzee. Science, 167, 86-87.

2 Plotnik, J. M., de Waal, F. M. B., and Reise, D. (2006). Self-recognition in an Asian elephant. Proceedings of the National Academy of Sciences, 103, 45-52.

3 Prior, H., Schwarz, A., and Gunturkun, O. (2008). Mirror-induced behavior in the magpie (Pica pica). PLOS Biology 6 (8) e202. doi:10.1371/journals.pbio.0060202

4 Morris, D. (1962). The biology of art. New York: Knopf.

5 Buchanan, G. (2015). The gorilla family and me. BBC Film Documentary.

6 Bekoff, M. (2001). Observations of scent-marking and discriminating self from others by a domestic dog (Canis familiaris): tales of displaced yellow snow Behavioural Processes, 55(2), 75-79 DOI:10.1016/S0376-6357(01)00142-5

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