Theory of mind is the ability to attribute mental states — beliefs, intents, desires, emotions, knowledge, etc. — to oneself, and to others, and to understand that others have beliefs, desires, intentions, and perspectives that are different from one’s own.

Theory of mind is crucial for everyday human social interactions and is used when analyzing, judging, and inferring others’ behaviors.

Deficits can occur in people with autism spectrum disorders, schizophrenia, attention deficit hyperactivity disorder, cocaine addiction, and brain damage suffered from alcohol’s neurotoxicity.

Although philosophical approaches to this exist, the theory of mind as such is distinct from the philosophy of mind.

Philosophical and psychological roots

Contemporary discussions of Theory of Mind have their roots in the philosophical debate—most broadly, from the time of Descartes’ Second Meditation, which set the groundwork for considering the science of the mind.

Most prominent recently are two contrasting approaches in the philosophical literature, to the theory of mind: theory-theory and simulation theory. The theory-theorist imagines a veritable theory—” folk psychology“—used to reason about others’ minds.

The theory is developed automatically and innately, though instantiated through social interactions. It is also closely related to person perception and attribution theory from social psychology.

The intuitive assumption that others are minded is an apparent tendency we all share. We anthropomorphize non-human animals, inanimate objects, and even natural phenomena.

Daniel Dennett referred to this tendency as taking an “intentional stance” toward things: we assume they have intentions, to help predict future behavior.

However, there is an important distinction between taking an “intentional stance” toward something and entering a “shared world” with it.

The intentional stance is a detached and functional theory we resort to during interpersonal interactions. A shared world is directly perceived and its existing structures reality itself for the perceiver. It is not just automatically applied to perception; it in many ways constitutes perception.

The philosophical roots of the relational frame theory (RFT) account of Theory of Mind arise from contextual psychology and refer to the study of organisms (both human and non-human) interacting in and with a historical and current situational context.

It is an approach based on contextualism, a philosophy in which an event is interpreted as an ongoing act inseparable from its current and historical context and in which a radically functional approach to truth and meaning is adopted.

As a variant of contextualism, RFT focuses on the construction of practical, scientific knowledge. This scientific form of contextual psychology is virtually synonymous with the philosophy of operant psychology.

Theory of mind in adults

Neurotypical adults have the theory of mind concepts that they developed as children (concepts such as belief, desire, knowledge, and intention).

A focal question is how they use these concepts to meet the diverse demands of social life, ranging from snap decisions about how to trick an opponent in a competitive game, to keep up with who knows what in a fast-moving conversation, to judge the guilt or innocence of the accused in a court of law.

Boaz Keysar, Dale Barr and colleagues found that adults often failed to use their theory of mind abilities to interpret a speaker’s message, even though they were perfectly well aware that the speaker lacked critical knowledge.

Other studies converge in showing that adults are prone to “egocentric biases”, whereby they are influenced by their own beliefs, knowledge or preferences when judging those of other people, or else neglect other people’s perspectives entirely.

There is also evidence that adults with greater memory and inhibitory capacity and greater motivation are more likely to use their theory of mind abilities.

In contrast, evidence from tasks looking for indirect effects of thinking about other people’s mental states suggests that adults may sometimes use their theory of mind automatically.

Agnes Kovacs and colleagues measured the time it took adults to detect the presence of a ball as it was revealed from behind an occluder. They found that adults’ speed of response was influenced by whether or not an avatar in the scene thought there was a ball behind the occluder, even though adults were not asked to pay attention to what the avatar thought.

Dana Samson and colleagues measured the time it took adults to judge the number of dots on the wall of a room. They found that adults responded more slowly when an avatar standing in the room happened to see fewer dots than they did, even when they had never been asked to pay attention to what the avatar could see.

It has been questioned whether these “altercentric biases” truly reflect automatic processing of what another person is thinking or seeing, or whether they instead reflect attention and memory effects cued by the avatar, but not involving any representation of what they think or see.

Different theories have sought to explain these patterns of results. The idea that the (TOM) is automatic is attractive because it would help explain how people keep up with the theory of mind demands of competitive games and fast-moving conversations.

It might also explain evidence that human infants and some non-human species sometimes appear capable of the theory of mind, despite their limited resources for memory and cognitive control.

The idea that (TOM) is effortful and not automatic is attractive because it feels effortful to decide whether a defendant is guilty or innocent, or whether a negotiator is bluffing, and economy of effort would help explain why people sometimes neglect to use their theory of mind.

Ian Apperly and Stephen Butterfill have suggested that people do in fact have “two systems” for the theory of mind,[46] in common with “two systems” accounts in many other areas of psychology.

On this account, “system 1” is cognitively efficient and enables the theory of mind for a limited but useful set of circumstances. “System 2” is cognitively effortful, but enables a much more flexible theory of mind abilities.

This account has been criticized by Peter Carruthers who suggests that the same core theory of mind abilities can be used in both simple and complex ways.

The account has been criticized by Celia Heyes who suggests that “system 1” theory of mind abilities do not require the representation of mental states of other people, and so are better thought of as “sub-mentalizing”.

Aging

In older age, the theory of mind capacities declines, irrespective of how exactly they are tested (e.g. stories, eyes, videos, false belief-video, false belief-other, faux pas).

However, the decline in other cognitive functions is even stronger, suggesting that social cognition is somewhat preserved. In contrast to the (TOM), empathy shows no impairments in aging.

There are two kinds of theory of mind representations: cognitive (concerning the mental states, beliefs, thoughts, and intentions of others) and affective (concerning the emotions of others).

Cognitive theory of mind is further separated into first order (e.g., I think she thinks that…) and second-order (e.g., he thinks that she thinks that…). There is evidence that cognitive and affective theory of mind processes are functionally independent of one another.

In studies of Alzheimer’s disease, which typically occurs in older adults, the patients display impairment with the second-order cognitive theory of mind, but usually not with the first-order cognitive or affective theory of mind.

However, it is difficult to discern a clear pattern of the theory of mind variation due to age. There have been many discrepancies in the data collected thus far, likely due to small sample sizes and the use of different tasks that only explore one aspect of the theory of mind.

Many researchers suggest that the (TOM) impairment is simply due to the normal decline in cognitive function.

Cultural variations

Researchers have proposed that five key aspects of the theory of mind develop sequentially for all children between the ages of three to five.

This five-step theory of mind scale consists of the development of diverse desires (DD), diverse beliefs (DB), knowledge access (KA), false beliefs (FB), and hidden emotions (HE).

Australian, American and European children acquire a theory of mind in this exact order, and studies with children in Canada, India, Peru, Samoa, and Thailand indicate that they all pass the false belief task at around the same time, suggesting that the children develop a theory of mind consistently around the world.

However, children from Iran and China develop theory of mind in a slightly different order. Although they begin the development of the theory of mind around the same time, toddlers from these countries understand knowledge access (KA) before Western children but take longer to understand false beliefs (FB).

Researchers believe this swap in the developmental order is related to the culture of collectivism in Iran and China, which emphasizes interdependence and shared knowledge as opposed to the culture of individualism in Western countries, which promotes individuality and accepts differing opinions.

Because of these different cultural values, Iranian and Chinese children might take longer to understand that other people have different, sometimes false, beliefs.

This suggests that the development of the theory of mind is not universal and solely determined by innate brain processes but also influenced by social and cultural factors.

Evolution

The evolutionary origin remains obscure. While many theories make claims about its role in the development of human language and social cognition few of them specify in detail any evolutionary neurophysiological precursors.

A recent theory claims that Theory of Mind has its roots in two defensive reactions, namely immobilization stress and tonic immobility, which are implicated in the handling of stressful encounters and also figure prominently in mammalian childrearing practices.

Their combined effect seems capable of producing many of the hallmarks of the theory of mind, e.g., eye-contact, gaze-following, inhibitory control, and intentional attributions.

Non-human

An open question is whether other animals besides humans have a genetic endowment and social environment that allows them to acquire a theory of mind in the same way that human children do.

This is a contentious issue because of the problem of inferring from animal behavior the existence of thinking or of particular thoughts, or the existence of a concept of self or self-awareness, consciousness, and qualia.

One difficulty with non-human studies of theory of mind is the lack of sufficient numbers of naturalistic observations, giving insight into what the evolutionary pressures might be on a species’ development of the theory of mind.

Non-human research still has a major place in this field, however, and is especially useful in illuminating which nonverbal behaviors signify components of theory of mind, and in pointing to possible stepping points in the evolution of what many claims to be a uniquely human aspect of social cognition.

While it is difficult to study the human-like theory of mind and mental states in species whose potential mental states we have an incomplete understanding, researchers can focus on simpler components of more complex capabilities.

For example, many researchers focus on animals’ understanding of intention, gaze, perspective, or knowledge (or rather, what another being has seen).

A study that looked at an understanding of intention in orangutans, chimpanzees, and children showed that all three species understood the difference between accidental and intentional acts.

Part of the difficulty in this line of research is that observed phenomena can often be explained as simple stimulus-response learning, as it is in the nature of any theorizers of mind to have to extrapolate internal mental states from observable behavior.

Recently, the most non-human theory of mind research has focused on monkeys and great apes, who are of most interest in the study of the evolution of human social cognition.

Other studies relevant to attributions theory of mind have been conducted using plovers and dogs, and have shown preliminary evidence of understanding attention—one precursor of the theory of mind—in others.

There has been some controversy over the interpretation of evidence purporting to show the theory of mind ability—or inability—in animals.

Two examples serve as demonstration: first, Povinelli et al. (1990) presented chimpanzees with the choice of two experimenters from whom to request food: one who had seen where food was hidden, and one who, by virtue of one of a variety of mechanisms (having a bucket or bag over his head; a blindfold over his eyes; or being turned away from the baiting) does not know, and can only guess. They found that the animals failed in most cases to differentially request food from the “knower“.

By contrast, Hare, Call, and Tomasello (2001) found that subordinate chimpanzees were able to use the knowledge state of dominant rival chimpanzees to determine which container of hidden food they approached.

William Field and Sue Savage-Rumbaugh believe that bonobos have developed the theory of mind, and cite their communications with a captive bonobo, Kanzi, as evidence.

In a 2016 experiment, ravens Corvus corax were shown to take into account visual access of unseen conspecifics. The researchers argued that “ravens can generalize from their own perceptual experience to infer the possibility of being seen”.

A 2016 study published by evolutionary anthropologist Christopher Krupenye brings new light to the existence of Theory of Mind, and particularly false beliefs, in non-human primates.