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Comparative theory of mind

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Comparative theory of mind is a field of comparative social cognition an involves the question of whether animals behave in a way which suggests they take into account hte intentions, desires, beliefs and goals of their conspecifics. The lion's share of research in this field has been conducted on chimpanzees, however research in other primates and non-primates is steadily accumulating. 

Research into nonhuman theory of mind has studied animals abilties in various domains, including: understanding goals and intentions, deception, knowledge attribution and self-recognition. All of these abilities require animals to understand the minds of others, however they may reliable on different infomation-processing structures.

Animals which perform well on one theory of mind task do not necessarily perform well on others. Chimpanzees, for example, can understand other's intentions, goals and recognise themselves in a mirror, however no study has yet shown that chimpanzees can understand false beliefs, which is a commonly-used test of theory of mind in humans.[1] Another example, is that crows will re-hide items of hidden food when a conspecific is observing them, suggesting a theory of mind (by understanding the intention of another to steal their food), however, when a mirror is placed in the cage, crows will re-hide food (because they think another bird is there), showing that they lack self-recognition. [2]

Theory of Mind in ChimpanzeesEdit


Povinelli (1993) pictures

Self-exploratory behaviour exhibited in the first 4 pictures, and the bottom picture shows a juvenile touching a spot of dye on the eyebrow during the mark test.

Self-recognition in a mirror is a well-known test of theory of mind in both humans and nonhuman animals. Self-recognition can be exhibited several ways: (1) the gradual decline of social and aggressive responses to a mirror can be seen as evidence that the animal acknowledges that it is not someone else in the mirror, (2) "self-exploratory" behavior in front of a mirror such as exploring hard-to-see places (see picture), and (3) the most convicing evidence comes from "mark tests". In mark tests, dye is put on a subjects face and sometimes arm (for a control) and observers measure the amount of time subjects spend touching these areas. Touching the arm but not the face suggests that the individual does not recognise the individual in the mirror. Gallup (1970) first argued that the capacity to recognise one's self in the mirror "implies a concept of self... [and] the ability to project, as it were, proprioceptive infomation and kinesthetic feedback onto the reflected visual image"[3]. Gallup (1975) has gone further to argue that passing the mirror test requires the organism to become the object of its own attention, what he called "self-awarenes". [4] Other have similarly argued that in children, passing the mirror test reflects self-awareness [5], however others have disagreed over what exactly is measured in this test. Intruigingly, only great apes, humans, dolphins and elephants have been shown to pass tests of self-recognition, whereas other animals tested (monkeys, fish, dogs, cats and parrots) have not reliably shown evidence of self-recognition. [6]

At the first sighting of their reflection in a mirror, most apes react as if they are confronted by a conspecific and direct a variety of behaviors towards the apparition. [7] However, after experience with a mirror, most great apes (chimpanzees, orang-utans and gorillas) conduct seemingly self-exploratory behaviors in a mirror, such as looking at previously not-visible areas of the body. [8][9] The time it takes for apes to recognise themselves in a mirror was initally reported to be 2-3 days of 8 hour exposures, [10] however other reports have shown that self-exploratory behavior often emerges within the first 30 minutes of exposure to a mirror, similarly to humans.[11] However, unlike in humans, around 25% of chimpanzees aged between 8-15 showed no evidence of self-recognition, and only half of those that did passed the mark test within 30 minutes. 

Understanding goals and intentionsEdit

In social situations, prediction of other's behavior in novel situations which one cannot learn "behavioral rules" may be useful. In the terminology of Piaget, egocentric animals cannot predict others behavior.  A spate of research in the 1990s casted doubt on the abilties of animals in this domain, but experimenters using different methods have recently provided a lot of evidence that, in fact, at least some primates can understand goals and intentions. 

One experiment which intially casted doubt on the theory of mind abilties of apes was conducted by Povinelli & Eddy. [12] Chimpanzees where taught to beg for food from an experimenter. After satisfactory performance, they were tested to see if they preferentially begged towards an experimenter whose eyes were visible to them, or to another experimenter whose eyes were occluded. Various conditions were used such as one individual had a bucket on their head and another did not, or one was lying facing the subject and the other lying facing the other way. The results suggested that the chimpanzees were equally likely to beg to either subject across all but one condition[13], which did not provide solid evidence of theory of mind. A null result does not necessarily disprove that chimpanzees have a theory of mind, since there are many other reasons why chimpanzees may fail this task. [14] However, the 6 chimpanzees used by Povinelli & Eddy were aged between 4-5, however even at this age nearly no chimpanzees show self-recognition behaviour in a mirror (see below for more infomation), which is present in around 20% of 6-7 year olds and 75% of 8-15 year olds. Human children aged 2 can understand that another person cannot see an object from a perspective different to theirs, however they struggle until the age of 4 to understand that other's experience of seeing is different until age 4. [15]

Since Povinelli and Eddy's research, there has been a spate of new studies which unambigiously show that chimpanzees can understand other's goals and intentions. For example, chimpaznees will imitate a human operating an apparatus with a novel body part such as a foot, but they won't do this when the human using a foot when their hands are occupied carrying a bucket. This suggests thgat they can understand that the human's intentions to use their hands, but that they cannot use their hands at that given time. [16] When in a task where a human and a chimpanzee compete for food from an apparatus, chimpanzees will prefer to use methods which conceal their approach from the very first trials (ruling out trial-and-error learning). [17] Chimpanzees are also more likely to use gestural communication when conspecifics or humans are oriented towards them, and position themselves in front of others before gesturing. [18]

False Belief UnderstandingEdit

If chimpanzees can understand the intentions and goals of others in many different contexts,[19] then it it would seem to follow that they can also understand that the knowledge of others can be false. However, no experiment has shown to date that chimpanzees or any other animal are able to do this. False-belief understanding develops quite late in humans, which suggests that it requires more complex cognition, which might be beyond nonhuman animals. Human infants understand that others have goals and intentions before their second birthday, however some children only begin to pass the Sally-Anne task at around 4 years of age. [20]

The development of false belief understanding in children can be measured with the classic "Sally-Anne task". The child is asked to name the two puppets (Sally and Anne) to test for name recall, and then Sally hides a marble in one box, leaves, then Anne arrives and puts the marble into her own box. When Sally arrives, the child is asked which box will Sally look for her marble. No children under 4 can complete this task, but most (86%) children aged 6-9 can complete the task. [21] Nonverbal versions of this task have been developed for use in infants and nonhuman animals, however this research has shown to date that apes are not capable of false-belief understanding.

A version of the Sally-Anne task was presented to chimpanzees and orang-utans by Josep Call & Michael Tomasello. [22] Here, the hider (the equivalent of Sally in the Sally-Anne task) hides food in a box in front of the communicator (Anne from the Sally-Anne task), and switches the locations of the two boces when the communicator's back is turned in the corner of the room. When the communicator comes back, they mark the box in the location the food used to be in, and the two boxes are pushed towards the chimpanzee who is watching the spectacle through a caged area. As many have pointed out [23], animals may not understand the gestures of the human demonstrators, and they may be more likely to show evidence of false belief understanding in studies with fellow conspecifics. 

Hare (2001) Pictures jpg

Experimental set up of Hare (2001).

Brian Hare and colleagues also failed to find evidence of false belief understanding using chimpanzees understanding of of conspecifics mental states rather than those of human experimenters. In their experiment, food was placed in a room which was connected to two seperate cages, whilst the chimpanzees were observing. In one experiment, the dominant chimpanzee either did or did not witness the food being placed behind a occluder (the dominant chimpanzee was replaced in the second condition). In another experiment, the food was witnessed by the dominant chimpanzee to be placed behind the occluder, however there was also food behind the other occluder which the dominant did not see. If chimpanzees understood that other chimpanzees were ignorant/informed, they would collect the food before the dominant saw (which they did). However, if chimpanzees also understood that the knowledge of others knowledge could be incorrect, they would also quickly retrieve food in the second experiment, however this did not occur. The researchers, however, argue that other factors other than theory of mind may explain the negative finding- for example with two pieces of food in the set up the competitive nature of the task may have diminished. 

See alsoEdit


  1. Call, J. & Tomasello, M. (2008) Does the chimpanzee have a theory of mind? 30 years later. Trends in Cognitive Sciences, 12, 5, 187-192.
  2. Pearce, J.M. (2008) Animal Learning and Cognition. New York: Psychology Press.
  3. Gallup, G.G., Jr. (1970) Chimpanzees: Self-Recognition. Science, 167, 86-87.
  4. cited in, Povinelli, et al. (1993) Self-recognition in Chimpanzees (Pan troglodytes): Distribution, Ontogeny, and Patterns of Emergence. Journal of Comparative Psychology, 107, 4, p.347.
  5. e.g. Lewis, M. & Brooks-Gunn, J. (1979) Social Cognition and the acquisiton on the self. New York: Plenum Press.
  6. One report of self-recognition in tamarins has not been replicated, see Pearce, J.M. (2008) Animal Learning and Cognition. New York: Psychology Press.
  7. Gallup, G.G., Jr. (1970) Chimpanzees: Self-Recognition. Science, 167, 86-87.
  8. Povinelli, et al. (1993) Self-recognition in Chimpanzees (Pan troglodytes): Distribution, Ontogeny, and Patterns of Emergence. Journal of Comparative Psychology, 107, 4, 347-372.
  9. Pearce, J.M. (2008) Animal Learning and Cognition. New York: Psychology Press.
  10. Gallup, G.G., Jr. (1970) Chimpanzees: Self-Recognition. Science, 167, 86-87.
  11. Povinelli, et al. (1993) Self-recognition in Chimpanzees (Pan troglodytes): Distribution, Ontogeny, and Patterns of Emergence. Journal of Comparative Psychology, 107, 4, 347-372.
  12. Povinelli, D.J. & Eddy, T.J. (1996) What young chimpanzees know about seeing. Monographs of the Society for Research in Child Development. 61, 1-152.
  13. After enough practise, chimpanzees learnt to beg to the correct experimenter when the face of the other experimenter is covered (i.e. with a bucket or screen) but when retested a year later, they begged randomly to either experimenter. This suggests that the chimpanzees used learning rules to infer which experimenter to beg to.
  14. see summary in Nissani, M. (2004) Theory of Mind and Insight in Chimpanzees, Elephants, and Other Animals? IN: Rogers, L.J. & Kaplan, G. (eds.) Comparative Vertebrate Cognition: Are Primates Superior to Non-Primates, New York: Kluwer Academic, pp. 227-258.
  15. Reaux, J.E., Theall, L.A. & Povinelli, D.J. (1999) A Longitudinal Investigation of Chimpanzees' Understanding of Visual Perception. Child Perception, 70, 2, 275-290.
  16. Buttelman, D. et al, (2007) Encultured chimpanzees imitate rationally. Developmental Science. 10, F31-F38.
  17. Melis, A.P. et al. (2006) Chimpanzees conceal visual and auditory information from others. Journal of Comparative Psychology. 120, 142-162.
  18. Call, J. & Tomasello, M. (2008) Does the chimpanzee have a theory of mind? 30 years later. Trends in Cognitive Sciences, 12, 5, 187-192.
  19. Call, J. & Tomasello, M. (2008) Does the chimpanzee have a theory of mind? 30 years later. Trends in Cognitive Sciences, 12, 5, 187-192.
  20. Kaminski, K., Call, J. & Tomasello, M. (2008) Chimpanzees know what others know, but not what they believe. Cognition, 109, 224-234
  21. however around 20% of children's failures between 6-9 because they failed to remember the initial location correctly; Wimmer, H. & Perner, J. (1983) Beliefs about beliefs: Representation and constraining function of wrong beliefs in young children's understanding of deception. Cognition, 13, 103-128.
  22. Call, J. & Tomasello, M. (1999) A Nonverbal False Belief Task: The Performance of Children and Great Apes. Child Development, 70, 381-395.
  23. see introduction; Kaminski, K., Call, J. & Tomasello, M. (2008) Chimpanzees know what others know, but not what they believe. Cognition, 109, 224-234.

Further readingEdit


  • Pearce, J.M. (2008) Animal Learning & Cognition. Psychology Press. [Chapter 12 contains short introduction to the experiments used to assess theory of mind]


    • Call, J. & Tomasello, M. (2008) Does the chimpanzee have a theory of mind? 30 years later. Trends in Cognitive Sciences, 187-192. 
  • Emery, N.J. & Clayton, N.S. (2009). Comparative Social Cognition. Annual Review of Psychology, Vol. 60: 87-113 DOI: 10.1146/annurev.psych.60.110707.163526

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