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Theory of mind
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Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own.
Theory of mind is different from philosophy of mind, although there are philosophical approaches to issues raised in discussions of theory of mind.
Interpersonal understanding of mental states
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others.
Discussion
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Encyclopedia
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own.
Theory of mind is different from philosophy of mind, although there are philosophical approaches to issues raised in discussions of theory of mind.
General category usage
In developmental psychology, theory of mind is a basic understanding of how the mind works and how it influences behavior.
Interpersonal understanding of mental states
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others. As originally defined, it enables one to understand that mental states can be the cause of—and thus be used to explain and predict—others’ behavior. Being able to attribute mental states to others and understanding them as causes of behavior means, in part, that one must be able to conceive of the mind as a “generator of representations” and to understand that others’ mental representations of the world do not necessarily reflect reality and can be different from one’s own. It also means one must be able to maintain, simultaneously, different representations of the world. It is a ‘theory’ of mind in that such representations are not "directly observable". Many other human abilities—from skillful social interaction to language and most importantly executive functions use—are said to involve a theory of mind.
Beyond the basic definition of ToM, there is considerable debate as to precisely what other kinds of abilities and understandings constitute a theory of mind, when these abilities develop, and who can be said to have a theory of mind. How one defines the basic mental states that underlie ToM structures the possibilities and limits of the field. Inherent in ToM is the understanding that others are intentional agents, that is, individuals whose behavior is goal- or perception-driven—and so debate about ToM has also reignited previous arguments on the nature of intentionality. In addition, efforts at defining the "mind"—generally understood as the totality of one’s conscious thoughts and perceptions—are relevant to the discussion of ToM. Although these debates are important, they do not inhibit the ToM research and progress in the fields of philosophy, psychology, and neuroscience. In fact, empirical research often sheds light back on the nature of these concepts.
Research on theory of mind in a number of different populations (human and animal, adults and children, normally- and atypically-developing) has grown rapidly in the almost 30 years since Premack and Woodruff's paper "Does the chimpanzee have a theory of mind?", as have the theories of theory of mind. The emerging field of social neuroscience has also begun to address this debate, by imaging humans while performing tasks demanding the understanding of an intention, belief, or other mental state.
Theory of mind appears to be an innate potential ability in humans (and, some argue, in certain other species), but one requiring social and other experience over many years to bring successfully to adult fruition. It is probably a continuum, in the sense that different people may develop more, or less, effective theories of mind, varying from very complete and accurate ones, through to minimally functional. It is often implied or assumed (but not stated explicitly) that this does not merely signify conceptual understanding "other people have minds and think," but also some kind of understanding and working model that these thoughts and states and emotions are real and genuine for these people and not just ungrounded names for parroted concepts. Empathy is a related concept, meaning experientially recognizing and understanding the states of mind, including beliefs, desires and particularly emotions of others without injecting your own, often characterized as the ability to "put oneself into another's shoes."
Philosophical roots
Contemporary discussions of ToM have their roots in 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 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. The mental states attributed to others are unobservable—theoretical notions that explain and predict behavior in the same way that doctors interpret abnormal blotches on an x-ray as cancerous tumors—and yet knowable by intuition or insight.
On the other hand, simulation theory suggests ToM is not, at its core, theoretical. Two kinds of simulationism have been proposed. Both hold that people generally understand one another by simulating being in the other's shoes. One version (Alvin Goldman's) emphasizes extrapolating from each one's own mental experience to the other's. The second version of simulation theory proposes that each person comes to know her own and others' minds through what Robert Gordon names a logical "ascent routine" which answers questions about mental states by re-phrasing the question as a metaphysical one. For example, if Zoe asks Pam, "Do you think that dog wants to play with you?", Pam would ask herself, "Does that dog want to play with me?" to determine her own response. She could equally well ask that to answer the question of what Zoe might think.
One of the differences between the two theories that have influenced psychological consideration of ToM is that theory-theory describes ToM as a detached theoretical process that is an innate feature, whereas simulation theory portrays ToM as a kind of knowledge that allows one to mimic the mental state of another person. These theories continue to inform the definitions of theory of mind at the heart of scientific ToM investigation.
Theory of mind development
Earlier in the twentieth century, Piaget articulated a view with similarities to ToM: that in early childhood egocentrism, a child does not understand that others’ views and thoughts differ from his or her own. There is now general agreement among researchers that human children pass tests of theory of mind much earlier than they leave Piaget's egocentric stage—by the age of 3 or 4 years. There is considerable disagreement regarding which behaviors necessarily indicate the presence of a developing theory of mind in young (1- to 3-year-old) humans. Much research focuses on investigating behaviors which may be precursors to the development of a fully functional theory of mind. These behaviors include joint attention, gaze following, proto-declarative pointing, comprehending objects' animacy, and awareness of others as intentional agents.
Gaze following—following another's gaze with one's own—is seen in infants by about the age of six months, while markers of joint attention, including shared mutual gaze, appear later, around the age of 9-12 months. Additionally, behaviors such as proto-declarative pointing—pointing in order to draw another's attention to an object in the environment—also emerge around the end of the first year. This ability to engage in shared attention is considered to be crucial for a child to learn about his or her social environment. A longitudinal study conducted by Charman et al. (2000) demonstrated that children who displayed the highest rates of joint attention at 20 months were generally the same children who scored highest on theory of mind tasks at 44 months. Some researchers believe that these behaviors and social referencing (using the emotional response of others to determine one's own response to a novel object or situation) suggest that children are beginning to have an awareness of adults' internal, mental functioning.
An ability to distinguish between animate and inanimate objects represents another step along the path toward development of a theory of mind. In studies conducted to answer the question of when people attribute animacy to objects, Tremoulet and Feldman (2000) demonstrated that objects that were perceived to be most animate were those whose motion appeared to violate laws of Newtonian physics or those moving objects that appeared to have a goal. (Most normally developing humans will acquire the ability to distinguish between animate and inanimate objects.)
After learning to define certain objects as animate, children can then begin to develop the concept of other beings as intentional "agents." An agent is an object that acts in a goal-directed manner, essentially planning actions and then carrying them out in the most efficient way possible in order to attain some end. Using a habituation procedure, Gergely et al. (1995) found that 12-month-old children were able to demonstrate an understanding that intentional agents act in rational ways. Meltzoff and Moore (1999) have shown that children as young as several hours or days old may mimic simple behaviors, which may be part of a developing ToM; other researchers have argued that 14- to 18-month-old infants are capable of understanding intention and so have a basic comprehension of others as intentional and mental agents. In a study of 18 month olds' ability to understand the intentions of others, Meltzoff found that children mimic intentional, but not unintentional, behaviors of (adult) humans in their environment, and that they imitate considerably less often when a machine is performing the behavior. This experiment suggests that infants younger than two years of age may be considering the intentions of others and interpret humans, and not machines, as intentional beings.
Empirical investigation
Whether children younger than 3 or 4 years old may have a theory of mind is a topic of debate among researchers. It is a challenging question, due to the difficulty of assessing what pre-linguistic children understand about others and the world. Tasks used in research into the development of ToM must take into account the umwelt—(the German word Umwelt means "environment" or "surrounding world")—of the pre-verbal child.
False-belief task
The canonical test of ToM ability is the false-belief task. One of the most important milestones in theory of mind development is gaining the ability to attribute false belief: that is, to recognize that others can have beliefs about the world that are wrong. To do this, it is suggested, one must understand how knowledge is formed, that people’s beliefs are based on their knowledge, that mental states can differ from reality, and that people’s behavior can be predicted by their mental states. Numerous versions of the false-belief task have been developed, based on the initial task done by Wimmer and Perner (1983).
In the most common version of the false-belief task (often called the ‘Sally-Anne’ task), children are told or shown a story involving two characters. For example, in one version, the child is shown two dolls, Sally and Anne, playing with a marble. The dolls put away the marble in a box, and then Sally leaves. Anne takes the marble out and plays with it again, and after she is done, puts it away in a different box. Sally returns and the child is then asked where Sally will look for the marble. The child passes the task if she answers that Sally will look in the first box where she put the marble; the child fails the task if she answers that Sally will look in the second box, where the child knows the marble is hidden, even though Sally cannot know, since she did not see it hidden there. In order to pass the task, the child must be able to understand that another’s mental representation of the situation is different from their own, and the child must be able to predict behavior based on that understanding.
The false-belief task has, in a number of studies, been modified so as to make certain that children who fail the tasks do so because they lack the ToM ability required, and not because the tasks are too cognitively demanding for them. Low-verbal false-belief tasks have tried to eliminate the possibility that the language of the task is too complicated for young or language-delayed children to understand. Such tasks often employ thought bubbles rather than explicit words to show a character thinking. The results of research using false-belief tasks have been fairly consistent: most normally-developing children are unable to pass the tasks until around the age of three or four. The conclusion from this research has thus been that most children do not begin to have any mature theory of mind abilities until this time. Passing these tasks does not necessarily mean that a child has a theory of mind like that of an adult—in fact, studies with mental verb acquisition show that at the age when children can pass the false-belief task, they still have difficulty in understanding differences between mental states—but being able to pass them is an indication that a child has developed the kinds of understanding, like false-belief, necessary for gaining adult ToM abilities, and that they are on their way to an adult ToM. Inability to pass the false-belief task–and thus the apparent inability to understand false belief–at an age when one is expected to be able to do so is usually taken as an indication of a developmental delay or other disruption that has affected ToM development.
Appearance-reality task
Other tasks have been developed to try to solve the problems inherent in the false-belief task. In the "appearance-reality", or "Smarties" task, experimenters ask children what they believe to be the contents of a box that looks as though it holds a candy called "Smarties." After the child guesses (usually) "Smarties," each is shown that the box in fact contained pencils. The experimenter then re-closes the box and asks the child what she thinks another person, who has not been shown the true contents of the box, will think is inside. The child passes the task if she responds that another person will think that there are "Smarties" in the box, but fails the task if she responds that another person will think that the box contains pencils. Gopnik & Astington (1988) found that children pass this test at age four or five years.
Other tasks
The "false-photograph" task is another task that serves as a measure of theory of mind development. In this task, children must reason about what is represented in a photograph that differs from the current state of affairs. Within the false-photograph task, there is either a location or identity change. In the location-change task, the child is told a story about a character that puts an object in one location (e.g., chocolate in a green cupboard) and takes a Polaroid photograph of the scene. While the photograph is developing, the object is moved to a different location (e.g., to a blue cupboard). The child is then asked two control questions, “When we first took the picture, where was the object? Where is the object now?” The subject is also asked a false-photograph question, “Where is the object in the picture?” The child passes the task if she correctly identifies the location of the object in the picture and the actual location of the object at the time of the question.
In order to make tasks more accessible for young children, non-human animals, and autistic individuals, theory of mind research has begun employing non-verbal paradigms. One category of tasks uses a preferential looking paradigm, with looking time as the dependent variable. For instance, Woodward found that 9-month-old infants preferred to look at behaviors performed by a human hand than those made by an inanimate hand-like object.
Autism
The theory of mind (ToM) impairment describes a difficulty someone would have with perspective taking. This is also sometimes referred to as mind-blindness. This means that individuals with a ToM impairment would have a hard time seeing things from any other perspective than their own. Individuals who experience a theory of mind deficit have difficulty determining the intentions of others, lack understanding of how their behavior affects others, and have a difficult time with social reciprocity. In 1985 Simon Baron-Cohen, Alan M. Leslie and Uta Frith published research which suggested that children with autism do not employ a theory of mind, and suggested that children with autism have particular difficulties with tasks requiring the child to understand another person's beliefs. These difficulties persist when children are matched for verbal skills (Happe, 1995, Child Development) and have been taken as a key feature of autism.
Method
Three groups of children – 20 children with autism, 14 children with Down's syndrome and 27 typically developing children – were used as participants for the experiment. The mean verbal mental age (vMA) of the children with autism (5 years, 5 months) was higher than the mean vMA of the children with Down's syndrome (2 years, 11 months) and the typically developing children (assumed 4 years, 5 months). The autistic group had an advantage in terms of age (experience) and verbal ability. If success on the task depended on these factors, then this group should have performed as well as or better than the other groups.
The 61 children were tested individually with the Sally-Anne test, a psychological test, used in developmental psychology to measure a person's social cognitive ability to attribute false beliefs to others.
Results
'Naming', 'reality', and 'memory' questions were answered correctly by all the children. However, the results were different for the questions about 'belief'. The results for children with Down’s Syndrome and typically developing subjects were quite similar. Of the 27 typically developing children, 23 passed the 'belief' question, and 12 out of 14 children with Down’s Syndrome passed the belief question on both trials (85% and 86% respectively). By contrast, only 4 of the 20 children classified as having autism (20%) passed the belief question on both trials. The 16 children with autism who gave the wrong response on both trials pointed to where the marble really was rather than to where Sally must believe it to be. The results seem to support the notion that children with autism may have underdeveloped theory of mind.
Discussion
The belief question was answered correctly by only 20% of the children with autism. This suggests that children with autism may be impaired in or lack a theory of mind. A characteristic of children with autism is a lack of engaging in pretend play. The use of dolls rather than real people could have confounded the findings. In 1988, the study was replicated by Alan M. Leslie and Uta Frith using people rather than dolls, and the results followed the same pattern as the original experiment.
Many individuals classified as having autism have severe difficulty assigning mental states to others, and they seem to lack theory of mind capabilities. Researchers who study the relationship between autism and theory of mind attempt to explain the connection in a variety of ways. One account assumes that theory of mind plays a role in the attribution of mental states to others and in childhood pretend play. According to Leslie, theory of mind is the capacity to mentally represent thoughts, beliefs, and desires, regardless of whether or not the circumstances involved are real. This might explain why individuals with autism show extreme deficits in both theory of mind and pretend play. However, Hobson proposes a social-affective justification, which suggests that a person with autism deficits in theory of mind result from a distortion in understanding and responding to emotions. He suggests that typically developing human beings, unlike individuals with autism, are born with a set of skills (such as social referencing ability) which will later enable them to comprehend and react to other people’s feelings. Other scholars emphasize that autism involves a specific developmental delay, so that children with the impairment vary in their deficiencies, because they experience difficulty in different stages of growth. Very early setbacks can alter proper advancement of joint-attention behaviors, which may lead to a failure to form a full theory of mind.
Brain mechanisms
In normally developing humans
Research on theory of mind in autism led to the view that mentalizing abilities are subserved by dedicated mechanisms that can (in some cases) be impaired while general cognitive function remains largely intact. Neuroimaging research has supported this view, demonstrating specific brain regions consistently engaged during theory of mind tasks. Early PET research on theory of mind, using verbal and pictorial story comprehension tasks, identified a set of regions including the medial prefrontal cortex (mPFC), and area around posterior superior temporal sulcus (pSTS), and sometimes precuneus and amygdala/temporopolar cortex (reviewed in ). Subsequently, research on the neural basis of theory of mind has diversified, with separate lines of research focused on the understanding of beliefs, intentions, and more complex properties of minds such as psychological traits.
Studies from Rebecca Saxe's lab at MIT, using a false belief versus false photograph task contrast aimed to isolate the mentalizing component of the false belief task, have very consistently found activation in mPFC, precuneus, and temporo-parietal junction (TPJ), right-lateralized. In particular, it has been proposed that the right TPJ (rTPJ) is selectively involved in representing the beliefs of others. However, this hypothesis remains controversial, because the same rTPJ region has been consistently activated during spatial reorienting of visual attention; Jean Decety from the University of Chicago and Jason Mitchell from Harvard have thus proposed that the rTPJ subserves a more general function involved in both false belief understanding and attentional reorienting, rather than a mechanism specialized for social cognition.
Functional imaging has also been used to study the detection of mental state information in Heider-Simmel-esque animations of moving geometric shapes, which typical humans automatically perceive as social interactions laden with intention and emotion. Three studies found remarkably similar patterns of activation during the perception of such animations versus a random or deterministic motion control: mPFC, pSTS, fusiform face area (FFA), and amygdala were selectively engaged during the ToM condition. Another study presented subjects with an animation of two dots moving with a parameterized degree of intentionality (quantifying the extent to which the dots chased each other), and found that pSTS activation correlated with this parameter.
A separate body of research has implicated the posterior superior temporal sulcus in the perception of intentionality in human action; this area is also involved in perceiving biological motion, including body, eye, mouth, and point-light display motion (reviewed in ). One study found increased pSTS activation while watching a human lift his hand versus having his hand pushed up by a piston (intentional versus unintentional action). Several studies have found increased pSTS activation when subjects perceive a human action that is incongruent with the action expected from the actor’s context and inferred intention: for instance, a human performing a reach-to-grasp motion on empty space next to an object, versus grasping the object; a human shifting eye gaze toward empty space next to a checkerboard target versus shifting gaze toward the target; a human turning on a light with his knee, versus turning on a light with his knee while carrying a pile of books; and a walking human pausing as he passes behind a bookshelf, versus walking at a constant speed. In these studies, actions in the "congruent" case have a straightforward goal, and are easy to explain in terms of the actor’s intention; the incongruent actions, on the other hand, require further explanation (why would someone twist empty space next to a gear?), and apparently demand more processing in the STS. Note that this region is distinct from the temporo-parietal area activated during false belief tasks. Also note that pSTS activation in most of the above studies was largely right-lateralized, following the general trend in neuroimaging studies of social cognition and perception: also right-lateralized are the TPJ activation during false belief tasks, the STS response to biological motion, and the FFA response to faces.
Neuropsychological evidence has provided support for neuroimaging results on the neural basis of theory of mind. A study with patients suffering from a lesion of the temporoparietal junction of the brain (between the temporal lobe and parietal lobe) reported that they have difficulty with some theory of mind tasks. This shows that theory of mind abilities are associated with specific parts of the human brain. However, the fact that the medial prefrontal cortex and temporoparietal junction are necessary for theory of mind tasks does not imply that these regions are specific to that function. TPJ and mPFC may subserve more general functions necessary for ToM.
Research by Vittorio Gallese, Luciano Fadiga and Giacomo Rizzolatti (reviewed in ) has shown that some sensorimotor neurons, which are referred to as mirror neurons, first discovered in the premotor cortex of rhesus monkeys, may be involved in action understanding. Single-electrode recording revealed that these neurons fired when a monkey performed an action and when the monkey viewed another agent carrying out the same task. Similarly, fMRI studies with human participants have shown brain regions (assumed to contain mirror neurons) are active when one person sees another person's goal directed action. These data have lead some authors to suggest that mirror neurons may provide the basis for theory of mind in the brain, and to support simulation theory of mind reading (see above)
However, there is also evidence against the link between mirror neurons and theory of mind. First, macaque monkeys have mirror neurons but do not seem to have a 'human-like' capacity to understand theory of mind and belief. Second, fMRI studies of theory of mind typically report activation in the mPFC, temporal poles and TPJ or STS, but these brain areas are not part of the mirror neuron system. Some investigators, like developmental psychologist Andrew Meltzoff and neuroscientist Jean Decety, believe that mirror neurons merely facilitate learning through imitation and may provide a precursor to the development of ToM.
In autism
Several neuroimaging studies have looked at the neural basis theory of mind impairment in subjects with Asperger's syndrome and high-functioning autism (HFA). The first PET study of theory of mind in autism (also the first neuroimaging study using a task-induced activation paradigm in autism) employed a story comprehension task,, replicating a prior study in normal individuals. This study found displaced and diminished mPFC activation in subjects with autism. However, because the study used only six subjects with autism, and because the spatial resolution of PET imaging is relatively poor, these results should be considered preliminary.
A subsequent fMRI study scanned normally developing adults and adults with HFA while performing a "reading the mind in the eyes" task—viewing a photo of a human’s eyes and choosing which of two adjectives better describes the person’s mental state, versus a gender discrimination control. The authors found activity in orbitofrontal cortex, STS, and amygdala in normal subjects, and found no amygdala activation and abnormal STS activation in subjects with autism.
A more recent PET study looked brain activity in individuals with HFA and Asperger’s while viewing Heider-Simmel animations (see above) versus a random motion control. In contrast to normally developing subjects, those with autism showed no STS or FFA activation, and significantly less mPFC and amygdala activation. Activity in extrastriate regions V3 and LO was identical across the two groups, suggesting intact lower-level visual processing in the subjects with autism. The study also reported reduced significantly less functional connectivity between STS and V3 in the autism group. Note, however, that decreased temporal correlation between activity in STS and V3 would be expected simply from the lack of an evoked response in STS to intent-laden animations in subjects with autism; a more informative analysis would be to compute functional connectivity after regressing out evoked responses from all time series.
A subsequent study, using the incongruent/congruent gaze shift paradigm described above, found that in high-functioning adults with autism, STS activation was undifferentiated while watching a human shift gaze toward a target and toward adjacent empty space. The lack of additional STS processing in the incongruent state may suggest that these subjects fail to form an expectation of what the actor should do given contextual information, or that information about the violation of this expectation doesn’t reach STS; both explanations involve an impairment in the ability to link eye gaze shifts with intentional explanations. This study also found a significant anticorrelation between STS activation in the incongruent-congruent contrast and social subscale score on the Autism Diagnostic Interview—Revised, but not scores on the other subscales.
Non-human theory of mind
As the title of Premack and Woodruff's 1978 article "Does the chimpanzee have a theory of mind?" indicates, it is also important to ask if 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, of the existence of a concept of self or self-awareness, or of particular thoughts.
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 claim to be a uniquely human aspect of social cognition. While it is difficult to study human-like theory of mind and mental states in species which we do not yet describe as "minded" at all, and about 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). 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, 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.
There has been some controversy over the interpretation of evidence purporting to show 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 which 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.
Tomasello and like-minded colleagues who originally argued that great apes did not have theory of mind have since reversed their position. Povinelli and his colleagues, however, maintain that Tomasello's group has misinterpreted the results of their experiments. They point out that most evidence in support of great ape theory of mind involves naturalistic settings to which the apes may have already adapted through past learning. Their "reinterpretation hypothesis" explains away all current evidence supporting attribution of mental states to others in chimpanzees as merely evidence of risk-based learning; that is, the chimpanzees learn through experience that certain behaviors in other chimpanzees have a probability of leading to certain responses, without necessarily attributing knowledge or other intentional states to those other chimpanzees. They therefore propose testing theory of mind abilities in great apes in novel, and not naturalistic settings. Kristin Andrews takes the reinterpretation hypothesis one step further, arguing that it implies that even the well-known false-belief test used to test children's theory of mind is susceptible to being interpreted as a result of learning.
See also
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