Theory of Mind: Comparing Bird Brain, Monkey Brain and Human Brain

Skye Harmony's picture

Imagine that you have been working extra hours and one night you come home late to find that your dog has chewed up your favorite pair of shoes. You might tell yourself that he is upset at you for not being there and thus took revenge by purposely ruining your things. It is not uncommon for people to ascribe emotions and motivations to their pets; we are so used to being aware and self-conscious that it seems natural to assume pets think the same way we do (6). However, this is probably a gross misestimation of your dog’s mental processes.

Theory of mind, “one of the cornerstones of human cognition” (1), is the ability to attribute thoughts and mental states (including desires and intentions) to other individuals. Animals who have theory of mind have “mental state concepts such as ‘believe’, ‘know’, ‘want’ and ‘see’, and… use them to predict and explain behavior” (5). The fields of sociobiology and evolutionary psychology are deeply invested in investigating theory of mind (1), and currently many researchers believe that this capacity is what separates humans from other animals. Humans acquire theory of mind by about age 4 (2) and it is central to most human behavior. We have yet to determine whether any other animal shares this cognitive ability.

It has already been established that a great variety of animals have high cognitive skills in many areas. Baboons live in complex, hierarchical societies and show evidence of hierarchically-structured, rule-governed representations of social relations. They understand complex social relationships not only involving themselves, but among all members of their troop, and they understand some causal relations. (8) Some fish and birds show evidence of similar social relationships and mental representations (3). Chimpanzees and crows can make and use tools- abilities that until a few decades ago were thought to be unique to humans.

Experiments testing imitation, self-recognition, social relationships, deception, role-taking (or empathy), and perspective-taking can lead us closer to an answer about whether nonhuman animals have theory of mind (5). Results have been mixed; only sometimes are results consistent with the possibility that animals demonstrate awareness of the mental states of others.

The list of apparent successes in finding evidence of theory of mind in animals is long. Chimpanzees demonstrate insightful problem solving (7), are spontaneously altruistic towards humans and other chimpanzees, and retaliate against other chimpanzees who have stolen from them (4). Elephants may be capable of recognizing that others can and cannot see things they themselves can see. Both chimpanzees and dolphins seem to recognize themselves in a mirror. Marmosets seem capable of imitation. (7) African cichlids (a type of fish) and birds of the corvidae family (including crows, jays, and ravens) appear to use simple logic to compute their chances of winning a fight against an individual they have not previously fought (3). And the use of deception has been well-documented in animals such as chimpanzees, capuchins (who bite into apples and try to “sell” them back to experimenters by hiding the bitten part), and western scrub jays (who re-hide food if they know another bird has seen them hide it). All of these observations imply that animals are capable of using causal reasoning and inferring the mental states of others.

On the other hand, there are instances in which animals seem to lack the necessary qualifications for theory of mind. Baboons sometimes fail to help their children cross a stream because they do not understand that the children do not have the same abilities as they do (9), and they do not call out to members of their troop who get lost. This suggests they do not understand that they can influence the mental states and behaviors of others. (2) Rhesus macaques do not seem to have the concept of false belief, or understanding that another individual is incorrect; they do not realize people with their backs turned do not have the same knowledge when the location of food is changed (1). Chimpanzees do not seem to understand that others see things- they are just as likely to beg from caregivers who are facing away and cannot see them than caregivers who are facing them and can see them (7).

However, no experiment to date conclusively proves that other animals do or do not possess theory of mind. Perhaps we just can’t help but think that other animals think and see the world the same way we do. It’s hard not to attribute theory of mind to them, but this may be misguided. It is hard to build reliable experiments testing theory of mind; unnatural testing conditions could alter results, and the observed behaviors could also be explained by genetic programming or trial and error learning. It is possible that other animals do not have theory of mind, but “brain systems dedicated to processing information about the regularities of the behaviors of others.” (7)

The study of theory of mind sparks many questions. First of all, what sets humans apart from other animals? Did theory of mind evolve uniquely in humans, or did it happen before humans branched off the tree of common ancestry we share with other species? Most researchers think language and theory of mind, which might be inextricably linked, make humans unique. Human children do better than chimpanzees on tests of social learning (imitation, nonverbal communication, gauging others’ intentions); these social cognition skills are probably what help humans maintain culture and society (4). Nonhuman animals seem to have highly developed cognitive abilities, but only in domains that are evolutionarily helpful to them, such as obtaining food and establishing dominance (1). Traits such as altruism and vengeance do occur in animals, but having conscious motivations behind them seems uniquely human (4).

However, we are constantly changing our definitions of cognition. It was previously thought that a neocortex was necessary in order for higher intelligence. But scientists are finding that birds are not so different from mammals in their cognitive abilities, and they lack a neocortex (instead having a nidopallidum caudolaterale). (3) If we do end up concluding that other animals have theory of mind, this discovery has enormous implications. If we found out that many animals are even more cognitively similar to us than we previously thought, we would probably think twice about testing on them and killing them for food.

Laurie Santos is not exaggerating when she says that primate behavior is “a window into the evolutionary past of human beings” (1). Figuring out the cognitive capacities of our close relatives (and not-so-close ones, too) can help answer questions about our own evolution, such as how and when different cognitive skills emerged. Social complexity may be related to theory of mind; birds that live in larger groups are better at using transitive inference to predict their position in the dominance hierarchy. (3) This suggests that the development of theory of mind may have been influenced by societal organization. Understanding theory of mind can also lead to clues about the development of language in humans or human ancestors; the cognitive abilities necessary for theory of mind are probably the same ones necessary for language. Tool use and theory of mind could both have influenced the development of language by providing the desire to communicate- tool use by supplying a need to explain to others how to use various tools, and theory of mind by endowing humans with the capacity to understand each other’s mental states. (9)

Exploring theory of mind also provides clues as to which animals have an I-function. I would expect that an I-function is necessary for theory of mind; in order to understand that others have mental states, one needs to acknowledge one’s own. But are the two abilities one and the same, or can an animal have an I-function and still lack the specific cognitive ability to attribute mental states to other individuals? Further experiments will help us disentangle the notions of the I-function and theory of mind. As we continue to create new experiments with the aim of figuring out which animals possess theory of mind, we will also be able to answer more general questions about awareness.





1. Adler, Jerry. "Thinking Like a Monkey." Smithsonian Jan. 2008. <>

2. American Psychological Association (2000, February 29). Baboons Have Voice And Communication But Not The "Theory Of Mind" To Understand How Their Communications Will Affect Others. ScienceDaily. <>

3. "Call Me "Bird Brain": a Bird's Eye View of Cognition." Neurophilosophy. 5 Feb. 2007. <>

4. Casselman, Anne. "Animal Insight." Smithsonian 11 Oct. 2007. <>

5. Heyes, C.M. "Theory of Mind in Nonhuman Primates." Behavioral and Brain Sciences 21 (1998): 101-134. <>

6. Katz, Jon. "Do Dogs Think?" Slate 6 Oct. 2005. <>

7. Nissani, Moti. "Theory of Mind and Insight in Chimpanzees, Elephants, and Other Animals?" Comparative Vertebrate Cognition: are Primates Superior to Non-Primates? Ed. Lesley Rogers and Gisela Kaplan. New York: Kluwer Academic/Plenum Publishers, January 2004. <>

8. Seyfarth, R.M., D.L. Cheney, and T.J. Bergman. "Primate Social Cognition and the Origins of Language." Trends in Cognitive Science 9 (2005): 264-266. <>

9. Wade, Nicholas. "How Baboons Think (Yes, Think)." The New York Times 9 Oct. 2007. <>


Carlos A.'s picture

Crossing the stream?

Reading the article, which is a nice one, made me wonder about certain humans and their inability to help their children or incur in infanticide. Is it a physical problem or education? Do we learn to care for our children (as the subject belongs to a responsible family) or as we have the resources to care for them (tangible and intangible).
Sorry for my bad English.

Goldy's picture

Theory of Mind - Dogs and Humans

If my dog sits and cocks her head when she wants something, this does not imply that she is thinking, "Goldy thinks this is cute. When she sees me acting cute, it makes her happy. When she is happy, she gives me something." Rather, she has learned that a certain type of behavior often results in what she wants. On the other hand, dogs sometimes interact with humans as if we were dogs, for example trying to get us to play when we shows signs of distress, which does seem to work with other dogs. .so, are they ascribing "dog mind" to us?

Marcia Malory's picture

Definition of TOM

If you expect a dog (or a very small child) to possess theory of mind, doesn't that mean that you, effectively, have a deficit in your own theory of mind? That is, you are expecting someone else to have the same mental capacities that you have. I think some people take theory of mind to mean assuming that others think the way you do and would act the same way that you would do in a situation, rather than understanding that others can have thoughts different from yours and might behave differently from you in the same situation.

Neha's picture


i think that people will not bother reading much on this website unless they are really desperate. You can inprove this by making a ven diagram instead. Make sure to make the dot points short and simple!

Paul Grobstein's picture

Theory of mind and I-function

An interesting question indeed .... "can an animal have an I-function and still lack the specific cognitive ability to attribute mental states to other individuals?" or vice versa? Perhaps humans also "fail to help their children cross a stream"? What is the difference between "theory of mind" and “brain systems dedicated to processing information about the regularities of the behaviors of others"?

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