Mirror test

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Baboon looking in mirror

The mirror test, sometimes called the mark test or the mirror self-recognition test (MSR), is a behavioural technique developed in 1970 by psychologist Gordon Gallup Jr. to determine whether a non-human animal possesses the ability of self-recognition.[1] Similar observations are used as an indicator of entrance to the mirror stage by human children in developmental psychology.


In 1970, Gordon Gallup Jr. experimentally investigated the possibility of self-recognition with two male and two female wild pre-adolescent chimpanzees, none of which had presumably seen a mirror previously. Each chimpanzee was put into a room by itself for two days. Next, a full-length mirror was placed in the room for a total of 80 hours at periodically decreasing distances. A multitude of behaviors were recorded upon introducing the mirrors to the chimpanzees.

Initially, the chimpanzees made threatening gestures at their own images, ostensibly seeing their own reflections as threatening. Eventually, the chimps used their own reflections for self-directed responding behaviors, such as grooming parts of their body previously not observed without a mirror, picking their noses, making faces, and blowing bubbles at their own reflections. Gallup expanded the study by manipulating the chimpanzees' appearance and observing their reaction to the mirror.[2]

Gallup anaesthetised the chimpanzees and then painted a red alcohol-soluble dye on the eyebrow ridge and on the top half of the opposite ear. When the dye dried, it had virtually no olfactory or tactile cues. Gallup then returned the chimpanzees to the cage (with the mirror removed) and allowed them to regain full consciousness. He then recorded the frequency which the chimpanzees spontaneously touched the marked areas of skin. After 30 minutes, the mirror was re-introduced into the room and the frequency of touching the marked areas again determined. The frequency of touching increased to 4-10 with the mirror present compared to only 1 when the mirror had been removed. The chimpanzees sometimes inspected their fingers visually or olfactorily after touching the marks.

Gallup conducted a follow-up study in which two chimpanzees with no prior experience of a mirror were anaesthetised, marked and observed. After recovery, they made no mark-directed behaviours either before or after being provided with a mirror.

Such mark-directed behavior includes turning and adjusting of the body to better view the mark in the mirror, or tactile examination of the mark with an appendage while viewing the mirror.[1]


The inspiration for the mirror test comes from an anecdote about Charles Darwin and a captive orangutan. While visiting the London Zoo in 1838, Darwin had occasion to observe an orangutan named Jenny throwing a tantrum after being teased with an apple by her keeper. This started him thinking about what the subjective experience of an orangutan is like.[3] Among other observations about how intelligent and human-like Jenny was, he also watched the ape gaze into a mirror and noted the possibility that the animal recognized itself in the reflection.[4]

Animals that have passed the test[edit]

European magpies have passed the mirror test

A large number of studies have investigated the occurrence of mirror-induced, self-directed behavior in animals of a great range of species. Most animals given a mirror respond with social behavior, such as aggressive displays, and continue to do so during repeated testing. However, only a small number of species have passed the mirror test. It should also be noted that even in the chimpanzee, the non-human species most studied and with the most convincing findings, clear-cut evidence of self-recognition is not obtained in all individuals tested.[5] Prevalence is about 75% in young adults and considerably less in young and aging individuals.[6]


  • Asian elephant: In a study in 2006, three female Asian elephants (Elephas maximus) were exposed to a large mirror to investigate their responses. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the mirror test. One of the elephants showed mark-directed behaviour whereas the other two did not.[7]


  • Chimpanzee: [1][8][9] Mirror tests with a juvenile (11 months old) male chimpanzee failed to reveal self-recognition.[10]
  • Orangutan:[citation needed] Mirror tests with a juvenile (2 years and 5 months old), male orangutan failed to reveal self-recognition.[10]
  • Gorilla: In 1982, mirror tests on two, zoo-reared gorillas failed to demonstrate self-recognition. The authors wrote "[These studies]...suggest that the gorilla may be the only great ape which lacks the conceptual ability necessary for self-recognition."[11] In 1993, a report was published that although six gorillas had previously failed to exhibit self-recognition, one individual that had been used extensively in cognition studies, Koko, had passed the mirror test (although without anaesthetic).[12] Western gorilla silverbacks react aggressively when shown a mirror in Gabon.[citation needed]


  • Bottlenose dolphin: Researchers in a study on two male bottlenose dolphins (Tursiops truncatus) observed their reactions to having a mark placed on them when presented with a mirror. Reactions such as repetitious head circling and close viewing of the eye or genital region which had been marked were reported as evidence of self-recognition in these marine mammals.[15][16]
  • Killer whales: Killer whales (Ocinus orca) and false killer whales (Pseudorca crassidens) may be able to recognize themselves in mirrors.[17]


Video of the responses of a European magpie in a mirror test: the magpie apppears to repeatedly attempt to remove the marks.
  • Eurasian magpie: The Eurasian magpie is the only bird to have passed the mirror test. Researchers applied a small red, yellow or black sticker to the throat of five Eurasian magpies where they could be seen by the bird only by using a mirror. The birds were then given a mirror. The feel of the sticker on their throats did not seem to alarm the magpies, however, when the birds with coloured stickers caught a glimpse of themselves in the mirror, they scratched at their throats - a clear indication that they recognised the image in the mirror as their own. Those that received a black sticker, invisible against the black neck feathers, did not react.[5]

Until the study on magpies, self-recognition was thought to reside in the neocortex area of the brain, however, this is absent in birds. Self-recognition in birds and mammals may be a case of convergent evolution, where similar evolutionary pressures result in similar behaviors or traits, although they arrive at them via different routes.

Species that have failed the test[edit]

In his original publication, Gallup reported that he also tested two male and two female adult stump-tailed macaques, and two adult rhesus monkeys, however, they failed to show any pattern of self-recognition behaviour.[1]

Rhesus monkeys (Macaca mulatta) do not pass the mirror test. However, it has been claimed they exhibit other behaviours in response to a mirror which indicate self-recognition.[18] Black-and-white colobus monkeys (Colobus guereza) fail to show direct or suggestive evidence of self-recognition.[19]

Criticisms of the test[edit]

Species with a non-visual primary sense[edit]

Dog looking in mirror

While the mirror test has been extensively conducted on primates, it may be of limited value when applied to animals who rely primarily on senses other than vision.[2][verification needed] The test has been accused of being overly anthropocentric, or at least unsuitable for many animals, due to its reliance on the visual sensory apparatus. Many animals rely on other senses in much greater amounts than humans do. For example, dogs' main senses are the olfactory sense and hearing, and vision comes only third. In fact, dogs mostly recognize individuals, both human and canine, by their smell and voice. It is speculated this is the reason dogs fail the mirror test. In light of this, the mirror test has been adapted to function through other sensory modalities, such as scent. Biologist Marc Bekoff developed a scent-based paradigm using dog urine in testing self-recognition in canines.[13][2] He tested his own dog, but his results were inconclusive.[20]

Lack of relevance of the mark[edit]

Animals may not recognize the mark as abnormal, or, may not be sufficiently motivated to react to it. However, this does not mean they are unable to recognise themselves. For example, in a mirror test conducted on three elephants by Diana Reiss and Joshua Plotnik in 2006, only one elephant passed, but the two elephants that failed still demonstrated behaviours that can be interpreted as self-recognition. Reiss and Plotnik say that the elephants might not have touched the mark because it was not important enough to them.[21]

Other reactions of animals to mirrors[edit]

Some researchers regard the mirror test as the "gold-standard" indication of self-awareness.[22][23] However only a small number of species have been recorded to pass it, and other levels of self-awareness in animals have been postulated from alternative experiments similar to the mirror test.

Primates, other than the great apes, have so far universally failed the mirror test. However, mirror tests with three species of Gibbon (Hylobates syndactylus, H.gabriellae, H. leucogenys) have shown convincing evidence of self-recognition despite the fact that the animals failed the standard version of the mirror test.[24]

Rhesus macaques have demonstrated a behavior indicative of at least a partial self-awareness.[25]

Capuchin monkeys react to their reflection either with hostility or affection. Mirror test studies have failed to show they are capable of spontaneous self-recognition.[26] Similar tests performed using video technology support these findings, but suggest that the monkeys do at least possess the raw input systems required for explicit self-recognition.[27]

Pigs can use visual information seen in a mirror to find food, and show evidence of self-recognition when presented with their reflection. In an experiment, 7 of the 8 pigs tested were able to find a bowl of food hidden behind a wall and revealed using a mirror. The eighth pig looked behind the mirror for the food.[28]

It is speculated that, in addition to the European magpie, some other Corvids have at least some degree of self-awareness, evidenced by behaviors such as re-caching food when initially watched by another bird, or hiding stolen shiny objects. These behaviors may also indicate that birds have a "theory of mind".[29]

In 1981, Epstein, Lanza and Skinner published an article in the journal Science, in which they argued that the pigeon is also capable of passing the mirror test, but only after extensive behavioral conditioning.[30][31] In the experiment, a pigeon was trained to look in a mirror to find a response key behind it, which the pigeon then turned to peck—food was the consequence of a correct choice (i.e., the pigeon learned to use a mirror to find critical elements of its environment). Next, the pigeon was trained to peck at dots placed on its feathers; food was, again, the consequence of touching the dot. The latter training was accomplished in the absence of the mirror. The final test was placing a small bib on the pigeon—enough to cover a dot placed on its lower belly. A control period without the mirror present yielded no pecking at the dot. When the mirror was revealed, the pigeon became active, looked in the mirror and then tried to peck on the dot under the bib. However, untrained pigeons have never passed the mirror test.[23]

Rouge test[edit]

A human child exploring his reflection

The rouge test is a specific version of the mirror test used with children.[32] Using rouge makeup, an experimenter surreptitiously places a dot on the nose and/or face of the child. The child is then placed in front of a mirror and their reactions are monitored; depending on the child's development, distinct categories of responses are demonstrated. This test is widely cited as the primary measure for mirror self-recognition in human children.[33][34][35]

Developmental reactions[edit]

From the age of 6 to 12 months, the child typically sees a "sociable playmate" in the mirror's reflection. Self-admiring and embarrassment usually begin at 12 months, and at 14 to 20 months most children demonstrate avoidance behaviors.[32] Finally, at 18 months half of children recognize the reflection in the mirror as their own[33] and by 20 to 24 months self-recognition climbs to 65%. Children do so by evincing mark-directed behavior; they touch their own nose and/or try to wipe the mark off.[32]

It appears that self-recognition in mirrors is independent of familiarity with reflecting surfaces.[34] In some cases the rouge test has been shown to have differing results, depending on sociocultural orientation. For example, a Cameroonian Nso sample of infants 18 to 20 months of age had an extremely low amount of self-recognition outcomes at 3.2%. The study also found two strong predictors of self-recognition: object stimulation (maternal effort of attracting the attention of the infant to an object either person touched) and mutual eye contact.[36] A strong correlation between self-concept and object permanence have also been demonstrated using the rouge test. [37]


The rouge test is a measure of self-concept; the child who touches the rouge on his or her own nose upon looking into a mirror demonstrates the basic ability to understand global awareness[citation needed]. Current views of the self in psychology position the self as playing an integral part in human motivation, cognition, affect, and social identity.[35] Other theorists have expounded on the significance of this time period in a child's life, such as psychoanalyst Jacques Lacan's use of a similar test in marking the mirror stage when growing up.[1][38]

Children gain the ability to pass the mirror test around 18 months of age[citation needed]. A specific version of the mirror test called the rouge test involves the use of rouge makeup as a test spot and asseses the degree of self-awareness based on the child's response to his or her mirror image.[13] It has also been noted that some animals,[2] young children,[14] and people who have their sight restored after being blind from birth,[13] often (at least initially) react to their reflection in the mirror as though it were another individual[citation needed].

Methodological flaws[edit]

There is some debate as to the interpretation of the results of the mirror test,[2] and researchers in one study have identified some potential problems with the test as a means of gauging self-awareness in young children.[39]

Proposing that a self-recognizing child may not demonstrate mark-directed behavior because they are not motivated to clean up their faces, thus providing incorrect results, the study compared results of the standard rouge test methodology against a modified version of the test.[39]

In the classic test, the experimenter first played with the children, making sure that they looked in the mirror at least three times. Then, the rouge test was performed using a dot of rouge below the child's right eye. For their modified testing, the experimenter introduced a doll with a rouge spot under its eye and asked the child to help clean the doll. The experimenter would ask up to three times before cleaning the doll themselves. The doll was then put away, and the mirror test performed using a rouge dot on the child's face. These modifications were shown to increase the number of self-recognizers.[39]

The results uncovered by this study at least suggest some issues with the classic mirror test; primarily, that it assumes that children will recognize the dot of rouge as abnormal and attempt to examine or remove it. The classic test may have produced false negatives, because the child's recognition of the dot did not lead to them cleaning it. In their modified test, in which the doll was cleaned first, they found a stronger relationship between cleaning the doll's face and the child cleaning its own face. The demonstration with the doll, postulated to demonstrate to the children what to do, may lead to more reliable confirmation of self-recognition.[39]

Self-recognition compared to self-awareness[edit]

On a more general level, it remains debatable whether recognition of one's mirror image implies self-awareness.[39]

See also[edit]


  1. ^ a b c d e Gallup, GG Jr. (1970). "Chimpanzees: Self recognition". Science 167 (3914): 86–87. doi:10.1126/science.167.3914.86. PMID 4982211. 
  2. ^ a b c d e f Stanley Coren. How Dogs Think. ISBN 0-7432-2232-6. 
  3. ^ Jonathan Weiner. Darwin at the Zoo. available at http://www.scientificamerican.com/article.cfm?id=darwin-at-the-zoo.
  4. ^ Carl Zimmer. The Descent of Man: The Concise Edition. excerpt available at http://carlzimmer.com/books/descentofman/excerpt.html.
  5. ^ a b Prior, Helmut; Schwarz, Ariane; Güntürkün, Onur (2008). "Mirror-induced behavior in the magpie (Pica pica): Evidence of self-recognition". PLoS Biology (Public Library of Science) 6 (8): e202. doi:10.1371/journal.pbio.0060202. PMC 2517622. PMID 18715117. Retrieved 21 August 2008. 
  6. ^ Povinelli, D.J., Rulf, A.B., Landau, K.R. and Bierschwale, D.T. (1993). "Self-recognition in chimpanzees (Pan troglodytes): distribution, ontogeny, and patterns of emergence". J. Comp. Psychol. 107: 347–372. doi:10.1037/0735-7036.107.4.347. 
  7. ^ Plotnik, J.M., de Waal, F.B.M. and Reiss, D. (2006). "Self-recognition in an Asian elephant". Proceedings of the National Academy of Sciences (abstract) 103 (45): 17053–17057. doi:10.1073/pnas.0608062103. 
  8. ^ Miller, Jason (2009). "Minding the Animals: Ethology and the Obsolescence of Left Humanism". American Chronicle. Retrieved 21 May 2009. 
  9. ^ Povinelli, Daniel; de Veer, Monique; Gallup Jr., Gordon; Theall, Laura; van den Bos, Ruud (2003). "An 8-year longitudinal study of mirror self-recognition in chimpanzees (Pan troglodytes)". Neuropsychologia 41 (2): 229–334. doi:10.1016/S0028-3932(02)00153-7. ISSN 0028-3932. 
  10. ^ a b Robert, S. (1986). "Ontogeny of mirror behavior in two species of great apes". American Journal of Primatology 10 (2): 109–117. doi:10.1002/ajp.1350100202. 
  11. ^ Ledbetter, D.H. and Basen, J.A. (1982). "Failure to demonstrate self-recognition in gorillas". American Journal of Primatology 2 (3): 307–310. doi:10.1002/ajp.1350020309. Retrieved 16 July 2014. 
  12. ^ Patterson, F. and Gordon, W. (1993). "The case for personhood of gorillas". In Cavalieri, P. and Singer, P. The Great Ape Project. St. Martin's Griffin. pp. 58–77. 
  13. ^ a b c d Archer, John (1992). Ethology and Human Development. Rowman & Littlefield. ISBN 0-389-20996-1. 
  14. ^ a b "Consciousness and the Symbolic Universe"
  15. ^ Marten, K. & Psarakos, S. (1995). "Evidence of self-awareness in the bottlenose dolphin (Tursiops truncatus)". In Parker, S.T., Mitchell, R. & Boccia, M. Self-awareness in Animals and Humans: Developmental Perspectives. Cambridge University Press. pp. 361–379. Retrieved 4 October 2008. 
  16. ^ Reiss, D. and Marino, L. "Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence". Proceedings of the National Academy of Sciences 98 (10): 5937–5942. doi:10.1073/pas.101086398. 
  17. ^ Delfour, F; Marten, K (2001). "Mirror image processing in three marine mammal species: Killer whales (Orcinus orca), false killer whales (Pseudorca crassidens) and California sea lions (Zalophus californianus)". Behavioural Processes 53 (3): 181–190. doi:10.1016/s0376-6357(01)00134-6. PMID 11334706. 
  18. ^ Lauwereyns, J., Rajala, A.Z., Reininger, K.R., Lancaster, K.M. and Populin, L.C. (2010). "Rhesus monkeys (Macaca mulatta) do recognize themselves in the mirror: Implications for the evolution of self-recognition". PLoS ONE e12865 5 (9). doi:10.1371/journal.pone.0012865. 
  19. ^ Shaffer, V. A., & Renner, M. J. (2002). "Black and white colobus monkeys (Colobus guereza) do not show mirror self-recognition". International Journal of Comparative Psychology 13: 154–159. 
  20. ^ http://www.psychologytoday.com/blog/canine-corner/201107/does-my-dog-recognize-himself-in-mirror
  21. ^ "Kids (and Animals) Who Fail Classic Mirror Tests May Still Have Sense of Self". 29 November 2010. Retrieved 30 May 2013. 
  22. ^ Bekoff M, Sherman PW (2004). "Reflections on animal selves". Trends in Ecology & Evolution 9 (4): 176–180. doi:10.1016/j.tree.2003.12.010. 
  23. ^ a b De Waal FB (2008). "The thief in the mirror". PLOS Biology 6 (8): e201. doi:10.1371/journal.pbio.0060201. 
  24. ^ http://www.uni-graz.at/zoowww/staff/Heschl/pdfs/Siamangs%20recognize%20their%20mirror%20image.pdf
  25. ^ Keim, Brandon (29 September 2010). "Monkeys See Selves in Mirror, Open a Barrel of Questions". Wired. Retrieved 1 October 2010. 
  26. ^ Roma, Peter; Silberberg, Alan; Huntsberry, Mary; Christensen, Chesley; Ruggiero, Angela; Suomi, Stephen (25 January 2007). "Mark tests for mirror self-recognition in Capuchin monkeys (Cebus Apella) trained to touch marks". American Journal of Primatology 69 (9): 989–1000. doi:10.1002/ajp.20404. ISSN 0275-2565. PMID 17253635. The results are consistent with the finding that no monkey species is capable of spontaneous mirror self-recognition. 
  27. ^ Anderson, James; Kuroshima, Hika; Paukner, Annika; Fujita, Kazuo (24 June 2008). "Capuchin monkeys (Cebus apella) respond to video images of themselves". Animal Cognition 12 (1): 55–62. doi:10.1007/s10071-008-0170-3. ISSN 1435-9448. PMID 18574604. Although they showed no signs of explicit self-recognition, the monkeys' behavior strongly suggests recognition of the correspondence between kinaesthetic information and external visual effects. 
  28. ^ Broom, D. M.; Sena, H.; Moynihan, K. L. (2009). "Pigs learn what a mirror image represents and use it to obtain information". Animal Behaviour 78 (5): 1037. doi:10.1016/j.anbehav.2009.07.027.  edit
  29. ^ Motluk, A. (2008). "Mirror test shows magpies aren't so bird-brained". New Scientist. Retrieved 14 July 2014. 
  30. ^ Epstein, Lanza; Skinner, RP; Skinner, BF (1981). ""Self-awareness" in the pigeon". Science 212 (4495): 695–696. doi:10.1126/science.212.4495.695. PMID 17739404. 
  31. ^ This is video of one such test
  32. ^ a b c Beulah Amsterdam (1972). "Mirror self-image reactions before age two". Developmental Psychobiology 5 (4): 297–305. doi:10.1002/dev.420050403. PMID 4679817. 
  33. ^ a b Lewis, M.; Brooks-Gunn, J. (1979). Social cognition and the acquisition of self. New York: Plenum Press. p. 296. ISBN 978-0-306-40232-6. 
  34. ^ a b Priel, Beatrice; de Schonen, Scania (1986). "Self-Recognition: A Study of a Population without Mirrors". Journal of Experimental Child Psychology 41 (2): 237–250. doi:10.1016/0022-0965(86)90038-X. PMID 3701250. 
  35. ^ a b Sedikides, C. & Spencer, S.J. (Eds.) (2007). The Self. New York: Psychology Press
  36. ^ Heidi Keller; Relindis Yovsi; Joern Borke; Joscha Kärtner; Henning Jensen; Zaira Papaligoura (2004). "Developmental Consequences of Early Parenting Experiences: Self-Recognition and Self-Regulation in Three Cultural Communities". Child Development 45: 1745–1760. 
  37. ^ BENNETT I. BERTENTHAL; KURT W. FISCHER (1978). "Development of Self-Recognition in the Infant". Developmental Psychology 4: 44–50. 
  38. ^ Lacan, J., Some reflections on the Ego in Écrits, org. published 1949.
  39. ^ a b c d e Jens B. Asendorpf; Veronique Warkentin and Pierre-Marie Baudonniere (1996). "Self-Awareness and Other-Awareness II: Mirror Self-Recognition, Social Contingency Awareness, and Synchronic Imitation". Developmental Psychology 32 (2): 313–321. doi:10.1037/0012-1649.32.2.313. 

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