REVIEWS
NEURAL SYSTEMS INVOLVED IN
‘THEORY OF MIND’
Michael Siegal* and Rosemary Varley‡
What is the nature of our ability to understand and reason about the beliefs of others — the
possession of a ‘theory of mind’, or ToM? Here, we review findings from imaging and lesion studies
indicating that ToM reasoning is supported by a widely distributed neural system. Some functional
components of this system, such as language-related regions of the left hemisphere, the frontal
lobes and the right temporal–parietal cortex, are not solely dedicated to the computation of mental
states. However, the system also includes a core, domain-specific component that is centred on the
amygdala circuitry. We provide a framework in which impairments of ToM can be viewed in terms of
abnormalities of the core system, the failure of a co-opted system that is necessary for performance
on a particular set of tasks, or the absence of an experiential trigger for the emergence of ToM.
*Department of Psychology,
University of Sheffield,
Western Bank, Sheffield
S10 2TP, UK.
‡
Department of Human
Communication Sciences,
University of Sheffield,
Sheffield S10 2TA, UK.
Correspondence to M.S.
e-mail:
[email protected]
doi:10.1038/nrn844
The human species is highly social — we constantly
build and maintain a variety of relationships with other
people. Crucial to this social competence is the possession of a theory of mind (ToM), which describes our
ability to understand the mental states — beliefs, desires
and intentions — of others, and to appreciate how these
differ from our own. The ability to recognize the nature
of beliefs is vital to family life and to the transmission of
culture. Understanding mental states, including the
false beliefs of, for example, William Shakespeare’s or
Jane Austen’s characters, underpins our appreciation of
literature, opera, drama and film. It animates our
humour and helps us to make sense of the complex pattern of social relationships that surround us, including
acts of deception.
Nearly 25 years ago, in an article that focused on the
cognitive capacities of non-human primates, Premack
and Woodruff 1 laid the foundation for modern research
on ToM, spanning psychology, animal behaviour, philosophy and neuroscience. Since then, considerable
attention has been directed towards determining the
linguistic and cognitive processes that underlie ToM reasoning and its corresponding neural structure. Studies of
ToM in children, and in people with profound deafness,
developmental and acquired language disorders, and
autism2–4, have guided our thinking on these problems.
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When tested on tasks that have been devised to
examine ToM reasoning (BOX 1), most 3-year-olds and
some 4-year-olds perform poorly, but most normal children succeed by 5 years of age. By contrast, people with
disorders such as autism often have a lingering impairment of ToM, and patients with brain lesions can
become impaired after their injury. A key issue concerns
the extent to which ToM reasoning is dependent on a
domain-specific, autonomous ‘core’ system that is
underpinned by a distinctive neuronal circuitry5–10. As
performance places demands on processing systems
such as language9,11, failure on a particular task might be
due to impairment of a core ToM system. Alternatively,
it might be due to a failure to recruit a component of a
widely distributed system that is not solely dedicated to
the computation of ToM states, but has been ‘co-opted’
to support performance in a particular cognitive modality. So far, research has not been definitive, as results
from functional imaging studies implicate large areas of
the cortex and subcortical structures (such as the cerebellum) in the attribution of mental states. However,
investigations of patients with cortical lesions indicate
that ToM reasoning can be sustained despite large areas
of damage in regions that are shown to be active in
imaging studies. From this research, several plausible
candidate systems for co-opting into reasoning on ToM
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Box 1 | ToM-reasoning tasks
Theory of mind (ToM) tasks often involve reasoning about the misleading contents of
containers and the unexpected locations of objects. These tasks can be presented in a
variety of verbal and pictorially illustrated formats. For example, in one type of
misleading-contents task — the Smarties task — subjects are shown a Smarties tube
(an M&Ms tube in the United States) that, when opened, is seen to contain pencils.
The test question concerns what another person, who has not been party to the
deception, will believe is in the tube97. In tasks that involve an unexpected location,
such as the ‘Sally–Anne task’, subjects are told about a character (Sally) who has a false
belief about the location of a marble. The character is described as having placed the
marble in a box; but while she is away, another character (Anne) moves it to a different
location. The test question addresses where Sally will look for the marble98. Other
tasks that relate to ToM have included interpreting a character’s mental state from his
or her facial expression63, interpreting intentions in response to biological motion49
and making inferences concerning mental states and intentions from verbal stories or
cartoons19,20,43.
Several forms of misleading-contents tasks have been developed with a view to
minimizing the verbal component of ToM performance. The fishing task shown in
the figure (adapted from Custer30) is one such example. In this test, children48 and
patients with aphasia45 are provided with pictures and asked to determine which of
the four alternatives is correct in indicating a boy’s false belief (that he has caught a
fish) and reality (that he has caught a boot). As shown in the top left panel, a flap
depicting reeds conceals the end of the line of the boy’s fishing rod. In the true-belief
or reality version of the picture (bottom left panel), removal of the flap reveals that
the protagonist has caught a fish. However, in the false belief (or thinking) version
(top right panel), removal of the flap reveals a boot. Once subjects view the picture
and lift and replace the flap, they are shown a separate picture of the boy with a blank
thought bubble above his head. Next to this picture are four small pictures. In the
false-belief tasks, two of these pictures are of distracter items, one shows the content
of the protagonist’s belief and the other shows the actual object. In the true-belief
condition, the true content is represented together with three distracters. In either
condition, the subjects are asked to indicate which of the four pictures shows what
the character is thinking and which shows the actual object concealed by the flap.
Other tasks involve pictures of a girl who thinks that she sees a tall boy over a fence
(true belief = a tall boy; false belief = a small boy standing on a box), a man who
thinks that he is reaching into a cupboard for a drink (true belief = a drink;
false belief = a mouse), and a man who thinks that he sees a fish in the sea
(true belief = a fish; false belief = a mermaid).
tasks have emerged. They include the neural mechanisms that are involved in processing language propositions, in EXECUTIVE FUNCTIONING (EF), and in tracking
objects and locations. Concerning the visuo-spatial
processing in object and location tracking, Frith and
Frith6–8 have proposed that the ability to ‘mentalize’ in
decoding the intentions of others has evolved from
the neural systems that are involved in perceiving the
motion of animate objects.
Two criteria can be used to distinguish between these
alternatives — dissociation and amelioration. The criterion of dissociation refers to the autonomy of the core
ToM system from potential co-opted systems. For
example, if the language system is a component of the
functional system that mediates ToM, its status as a
co-opted system can be established by examining
whether people with severe language disorders can pass
tests of ToM. Successful performance despite language
impairment would indicate that the language system
serves as a co-opted system that supports ToM reasoning, rather than as part of the core system. Regarding the
criterion of amelioration, let us consider the following
example. Children younger than 4 years and adults with
brain lesions often fail ToM tasks when they are presented with test questions in a standard format (“Where
will Sally look for her marble?”; see BOX 1). However,
performance can improve if the tasks are accompanied
by aids that minimize visuo-spatial memory demands
or if the test questions are presented in a manner that
explicitly signals the purpose and relevance of the tasks.
For example, by asking the question “Where will Sally
look first for her marble?”, which clearly refers to how a
character with a false belief might initially be misled in
searching for an object. Successful performance with
task modification would indicate that visuo-spatial
memory, in the case of this example, serves as a co-opted
system in ToM, rather than as part of the core system.
Research on the biological basis of ToM has indicated that reasoning out task solutions might depend on
the language system (in particular, on left-hemispheremediated grammatical abilities), the frontal lobes,
temporal–parietal regions (particularly in the right
hemisphere) and amygdala circuits. We examine the evidence in support of these four components as core or
co-opted systems that enable ToM reasoning using the
criteria of dissociation and amelioration, and discuss
what this evidence implies about the mechanisms that
underlie the emergence of ToM during childhood.
Language
?
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According to the view that has often been expressed on
the link between language and ToM, language provides
a structure that ‘scaffolds’ propositional reasoning
about mental states12–16. One specific claim is that syntax
enables humans to entertain false beliefs and to reason
out solutions to ToM tasks. For example, de Villiers and
de Villiers17 have proposed that proficiency in syntax is
crucial in supporting ToM reasoning, as the grammar
of natural language provides a code through which a
(false) proposition can be embedded within another,
such as “John thought (falsely) that the cookies were in
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Figure 1 | Structural magnetic resonance image in a
transverse plane from patient SA. This patient showed
preserved theory-of-mind performance, despite a large lefthemisphere lesion (white areas) that extended across the
perisylvian area, with associated enlargement of the ventricular
system. Reproduced, with permission, from REF. 10 © 2000
Elsevier Science.
EXECUTIVE FUNCTIONING
A cluster of high-order
capacities, which include
selective attention, behavioural
planning and response
inhibition, and the manipulation
of information in problemsolving tasks.
MIRROR NEURONS
A particular class of neurons,
originally discovered in the
ventral premotor cortex, that
code goal-related motor acts
such as grasping. Specifically,
mirror neurons require
action observation for their
activation; they become active
both when the subject makes a
particular action and when it
observes another subject making
a similar action.
APHASIA
A language impairment that is
acquired as a result of stroke or
other brain injury.
SPECIFIC LANGUAGE
IMPAIRMENT
A term that is often assigned
to a developmental language
disorder that cannot be
explained by any other
apparent environmental,
perceptual, cognitive or
motor cause.
the cupboard”. In this regard, positron emission
tomography (PET) imaging studies that are carried
out while subjects perform various versions of ToM
tasks have shown extensive activation of temporal lobe
structures that is either bilateral18,19 or localized to language areas of the left hemisphere20–22. In a study using
functional magnetic resonance imaging (fMRI),
Rizzolatti and his colleagues23 (see also REF. 24) reported
that MIRROR NEURONS in Broca’s area that are dedicated to
language processing are activated in response to witnessing goal-directed behaviour. These neurons seem to
form a cortical system that matches the observation
and execution of goal-related motor actions. It has
been suggested that the mirror neuron system could
underlie cognitive functions that are as wide-ranging
as language understanding and ToM25,26.
Do these observations implicate the neural regions
that are dedicated to language as part of the ToM core
system, or are they components of co-opted systems
that assist the ToM core? In functional imaging, this
issue is addressed using a subtraction design in which
the control condition differs from the ToM task only in
the requirement for interpretation of the mental states
of others. However, subtraction designs are complex
and require that there be a well-formulated model of the
functional components that are involved in particular
cognitive processes. Moreover, whereas imaging studies
have indicated specific brain regions in which activation
is correlated with performance on ToM-reasoning tasks,
such studies do not shed light on the regions that are
necessary for performance. To address this issue, it is
necessary to carry out neuropsychological studies of
NATURE REVIEWS | NEUROSCIENCE
patients. These cases provide insight into the corresponding cognitive architecture of the ToM system insofar
as they establish the status of a particular functional
component as core or as co-opted.
Recent investigations of individuals with severe
APHASIA have shown that ToM reasoning is retained
despite damage to left-hemisphere language centres,
and has remained intact even in a rare case in which the
person suffered a profound, selective impairment of
syntax that could be shown in tests of explicit grammatical
knowledge (FIG. 1 and BOX 2). However, the relationship
between language and ToM might be such that language mechanisms serve to configure ToM ability early
in life. For example, linguistic experience might provide
input to the ToM system that is essential to trigger its
initial development and subsequent refinement. The
limited evidence from children with SPECIFIC LANGUAGE
IMPAIRMENT (SLI) indicates that they succeed as readily as
normal children on ToM tasks27,28, and generally perform at a similar level to normal children on a range of
abstract non-verbal tasks. In the rare cases of children
with a subtype of SLI that is specific to grammar29, some
ability to construct language propositions is attained
that might serve to support ToM reasoning. Nevertheless, proficiency in grammar does not guarantee success
on ToM tasks, as normal 3-year-olds spontaneously
produce sentences that involve the syntax of complementation before they succeed on standard tests of
ToM. Moreover, they solve ‘pretence’ tasks that require
understanding of sentence complementation — tasks
that have the same structure as ToM tasks, except that
the story character is said to pretend, rather than to
think, that an object is in a (false) location30. The dissociation between language and other cognitive systems is
also compatible with recent discoveries on the genetics
of grammatical disorders, which indicate that such disorders do not characteristically encompass non-verbal
cognitive deficits31. Moreover, studies of genetic influences on ToM in children have shown that these seem to
be, for the most part, independent of genetic influences
on verbal ability32,33. So, studies of children converge with
data from adults in pointing to language as a co-opted
system that supports performance on ToM tasks.
Frontal lobes and executive functioning
ToM reasoning has also been seen to involve frontal
lobe structures that are associated with EF34. In many
tests of ToM, success involves inhibiting the potent
choice of the real location of an object, and choosing
instead the false location that would be represented in
the mind of a person with a false belief 35–37.
To examine the role of EF in ToM, Stuss et al.38
tested patients with brain damage that were divided by
site of lesion into right frontal, left frontal, right nonfrontal and left non-frontal groups. The patients were
tested in perspective-taking and deception tasks (BOX 3).
Frontal lobe patients, particularly those with rightsided lesions, had considerable difficulties with these
tasks. Other neuropsychological investigations have
shown an association between frontal lobe damage that
affects orbitofrontal circuitry and failure on ToM
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Box 2 | “If not in language centres, where is it?” asks patient SA
There has been a long tradition of examining the effects of aphasia on thinking and reasoning,
both to determine the fundamental characteristics of the disorder and to address the broader
question of the role of language in human cognition99–102. However, earlier research was often
imprecise in specifying the forms of thinking that might be mediated by language, and in the
nature and extent of language impairment that is seen in cases of aphasia.
In a recent series of experiments, the role of language propositions in mediating
performances on theory of mind (ToM) tasks was investigated in two men (SA and MR)
with severe aphasia; causal association and reasoning, and hypothesis generation and
testing, were also examined10,45,103. Both men had profound impairments of grammatical
ability, to the extent that neither was able to comprehend simple spoken or written
sentences, and both were unable to construct language propositions in either speech or
writing. Whereas MR retained some ability to make grammaticality judgements,
SA performed at chance levels on such tasks and showed a complete absence of syntactic
constructional ability. Despite these profound impairments of grammar, both patients
performed well on ToM tasks and on tests of causal association and reasoning. SA was also
able to generate hypotheses and to test them against evidence.
The evidence of sophisticated cognition extended beyond performances on experimental
tasks. SA was adept in using the communicative resources available to him, including written
single words, pantomime gesture, facial expression, and drawing to express complex ideas
and to seek information. The figure illustrates this capacity. The drawing was completed
during an interaction in which an investigator was seeking informed consent from SA for his
participation in an experiment. The first drawing (blue) was produced by the investigator,
explaining that the study addressed the issue of thinking in people with aphasia-causing
lesions. SA interrupted this explanation to ask a series of questions. Each of his drawings
represents a question as to whether an individual with a brain lesion at a particular site, or on
a particular scale, would have impaired thinking. In the sequence of drawings, SA has an
accurate knowledge of his own lesion size and location, of brain images in a horizontal plane,
and of how patient identifiers are generated in neuropsychological investigations.
WISCONSIN CARD SORTING TEST
A test that is used to measure
behavioural flexibility in which
subjects receive cards with
different symbols and are asked
to sort them by a certain feature
(such as their colour). After the
rule is learned, the subjects,
without warning, are required to
‘shift set’ and sort them by a
different feature (such as the
shape of the symbols). People
with prefrontal cortex lesions
show impaired performance on
this task and ‘perseverate’ —
they carry on sorting the cards
by a particular feature despite
being told that it is incorrect.
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tasks39,40. In a PET imaging study, Brunet et al.19 found
that the right medial prefrontal cortex is activated as
part of a complex pattern of cerebral activity on nonverbal ToM tasks that require subjects to choose an
appropriate ending to represent attribution of intention as represented in comic frames. Evidence of bilateral activation of medial prefrontal structures during
ToM reasoning comes from a series of imaging studies20,21,41–43. However, Rowe et al.44 found no significant
relationship between the performance of patients with
frontal lesions on ToM-reasoning tasks and a range of
EF measures that investigate the ability to select, inhibit,
monitor actions and make use of mental flexibility.
Dissociation between ToM performance and EF was
also reported in a recent case study45. In this case, ToM
reasoning was intact despite a severe impairment of EF
as measured by the WISCONSIN CARD SORTING TEST46.
Further evidence of dissociation between ToM and
EF comes from studies of people with autism. Many
patients with autism have great difficulty with ToM
reasoning, but are proficient in tests that have a similar
problem structure to ToM tasks but do not involve the
consideration of mental states. For example, they often
succeed on false photograph tasks in which an experimenter photographs an object in one location and then
moves it to a new location. On such tasks, individuals
with autism show the executive capacity to inhibit
knowledge of the current state of affairs in predicting
the location of the object in the photograph9. A similar
pattern of findings comes from studies of deaf children
of hearing parents, who, although proficient in a sign
language, also have ToM difficulties47,48. Therefore,
although EF and frontal lobe function is likely to be
essential for success on certain tasks, it is not sufficient to
underlie ToM reasoning and can be regarded as a
co-opted system that serves to sustain performance.
Right-hemisphere non-frontal areas
Frith and Frith6 have proposed that the ability to mentalize on ToM tasks might have evolved from the capacity
to detect the motion of animate agents and, subsequently,
to infer intentions from actions. A region of the superior temporal sulcus, particularly in the right hemisphere, responds to biological motion and receives
inputs from both the DORSAL AND VENTRAL VISUAL STREAMS49.
In this respect, imaging studies have shown that, in
addition to medial prefrontal activation that is associated with reasoning tasks related to ToM, there is extensive recruitment of right temporal–parietal areas. Ruby
and Decety50 (see also REFS 22,51) have reported that
the right inferior parietal cortex, the PRECUNEUS and the
somatosensory cortex are recruited in distinguishing
the perspectives of the self from those of others — an
ability that is relevant to knowing that the contents of
other people’s minds can be different from our own.
These results are in line with data from PET imaging
studies of spatial working memory that have found
increased activation in several overlapping righthemisphere sites, including the prefrontal, occipital,
parietal and premotor cortices52. There are several candidate hypotheses to account for the link between right
posterior areas and ToM performance. These include
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Box 3 | Design of a deception task
Stuss et al.38 designed a task to assess a
person’s ability to infer that someone is
attempting to enact a deception. In this task,
the examiner and subject were seated at
opposite sides of a table. There was a curtain
on the table held by a frame so that the area
behind the curtain was blocked from the
subject’s view. Behind the curtain, situated on
the examiner’s side of the frame, were two
white Styrofoam cups.When the curtain was
closed, the examiner hid a coin underneath
one of the two cups, the location of which was
viewed by an assistant on the examiner’s side
of the table (a). The curtain was then opened
and the assistant pointed to the wrong cup
(without the coin). The subject’s task was to
point to the cup where he or she thought the
coin had been hidden (b). For correct choices,
the subject kept the coin. For incorrect
choices, the assistant kept the coin.
On an analogous perspective-taking task,
there were two assistants — one sitting next to
the experimenter who could see under which
cup a coin was hidden with the curtain closed,
and one sitting beside the subject who did not
have this knowledge.After the object was
hidden, both assistants were positioned
behind the curtain.When the examiner
opened the curtain, the assistants pointed to
different cups — the assistant who had been
sitting next to the examiner pointed to the
correct one and the assistant who had been
sitting next to the subject pointed to the
incorrect one. The subject’s task was to locate
the hidden object.
DORSAL AND VENTRAL VISUAL
STREAMS
Visual information from V1 is
processed in two interconnected
but partly dissociable visual
pathways: a ‘ventral’ pathway
that extends into the temporal
lobe and is thought to be
primarily involved in visual
object recognition, and a ‘dorsal’
pathway that extends into the
parietal lobes and is thought to
be more involved in extracting
information about ‘where’ an
object is or ‘how’ to execute a
visually guided action towards it.
PRECUNEUS
An area of the inner surface of
the cerebral hemisphere, above
and in front of the corpus
callosum.
a
b
the involvement of right-hemisphere-dependent mechanisms in understanding the implications of conversations (independently of competence in syntax and
vocabulary), and in various sub-domains of visual processing, including tracking actions, the location of
objects and visuo-spatial working memory.
Findings from patients with brain lesions corroborate
the results from imaging research. People with lesions of
the right hemisphere consistently have difficulties on
tasks that involve an appreciation of the mental states of
others. In many cases, the frontal lobes are unimpaired
but lesions are present in more posterior cortical zones.
The capacity to understand the mental states of others
in people with lesions of the right hemisphere has been
examined with standard ToM tasks, but also with other
tasks that require judgements of intentions — for
example, whether an utterance was intended to be sincere or ironic. It has been known for some time that people with right-hemisphere damage in non-frontal areas
have considerable difficulty in interpreting indirect
requests and commands. They rely on the literal meanings of conversations and neglect pragmatic cues that
are relevant to deriving meaning from context, and
their understanding of the themes of narratives is
NATURE REVIEWS | NEUROSCIENCE
impaired53–55. For example, Siegal, Carrington and
Radel56 (see also REF. 57) presented patients with rightand left-hemisphere damage short vignettes, such as
“Sam thinks that his puppy is in the garage, but his
puppy instead is really in the kitchen”. The patients were
then asked to predict where the character that held a false
belief would search for his puppy. On such tasks, subjects
are required to recognize that the purpose of the
questioning is to determine whether they can detect how
others’ beliefs can initially be false. Therefore, they are
required to follow the implication that the standard test
question, “Where will a person (with the false belief)
look for the object?” means actually “Where will the person look first?” Yet patients with lesions of the right
hemisphere might assume that the purpose of the questioning is more straightforward — to test whether they
can predict the behaviour of others in achieving a goal. If
so, the question,“Where will Sam look for his puppy?”
might simply be interpreted as “Where does Sam have to
look for his puppy in order to find it?”Although patients
with right-hemisphere damage failed when asked the
test question in the standard, implicit form (“Where will
Sam look for his puppy?”), they succeeded on a more
explicit version of the question (“Where will Sam look
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first for his puppy?”). This question avoids the need to
make the inference in conversation that the question
refers to the character’s first attempt to retrieve an object.
Apart from the need to follow conversational inferences, ToM reasoning often involves the tracking of
objects and locations. Consequently, a crucial source
of errors in ToM tests of patients with right-hemisphere
lesions might be impairments of visuo-spatial processing.
In recent work58, providing patients with visual aids that
illustrated the relevant premises reduced the requirement
for object and location memory in ToM tasks. Patients
with either right or left lesions performed well when the
tasks were presented with visual aids, confirming earlier
findings that, with low memory demands, patients are
more likely to succeed40. But compared with patients with
left-hemisphere damage, those with right damage had
difficulty when the same tasks were presented only verbally. They also showed a significant impairment in their
ability to follow inferences in conversation on a test of
pragmatic awareness in language. Such findings indicate
again that, in an established cognitive architecture, various visuo-spatial mechanisms are co-opted elements
in ToM performance. Further research is needed to bolster this conclusion and, in particular, to seek evidence of
dissociation between the conversational difficulties
and visuo-spatial disturbances that can follow after
right lesions, and success on ToM tasks that have been
modified using visual aids to improve performance.
Medial temporal lobe–amygdala system
Current studies indicate that ToM reasoning is not
dependent on the possession of grammar, and that it is
not wholly reducible to EF capacity. Lowering the
demands for visuo-spatial representation improves performance. However, there is converging evidence that
amygdala structures and their connecting complex of
neural systems are at the core of the capacity to interpret
the mental states of others. One line of evidence comes
from investigations of people with autism. This disorder
is apparent early in a child’s development (it can be
identified before 30 months), and is diagnosed on the
basis of the presence of a triad of impairments — a failure to develop normal social relationships and interactions, impaired communication, and rigidity in
behaviour that is characterized by a lack of imagination
and repetitive behaviours59,60.
Research on the neuropathology of autism has been
influenced by Brothers61, who suggested the involvement
of three regions in social cognition — the medial temporal lobe–amygdala structures, the orbitofrontal cortex
and the superior temporal gyrus. The amygdala has an
important role in deriving the emotional significance of
objects and faces62. Stimulation of the amygdala in
humans results in fearful responses63. Structural and
functional imaging studies of people with autism, as well
as post-mortem investigations, have revealed abnormalities in both cortical and subcortical structures, including
the cerebellum. However, there have also been reports of
abnormalities in medial temporal lobe structures and,
specifically, in the amygdala complex18,64–66. Similarly,
abnormalities in the orbitofrontal cortex, medial frontal
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regions and regions of the temporal lobe have been identified67,68. These findings are consistent with evidence
from imaging studies of normal subjects, who show activation in these prefrontal and temporal regions when
performing ToM tasks. The importance of the amygdala
structures is supported by the work of Bachevalier69,70,
which has revealed socio-emotional disturbances in
monkeys after bilateral amygdala lesions. The behaviours
observed in lesioned monkeys have similarities with the
human autism syndrome, and include reduced initiation
of social contact, avoidance of contact with others,
stereotyped behaviours and abnormalities of communicative behaviours, such as facial expression, eye contact
and body postures. The manifestation of the behavioural
abnormalities might depend on several factors, such as
how and at what age the lesion took place71.
This converging evidence indicates that the amygdala system and its complex interconnections with prefrontal and temporal lobe structures could provide the
basis for a range of socio-cognitive behaviours. These
would include lower-level behaviours, such as determining the emotional significance of stimuli that are
present across a wide range of species. However, when
the core system is combined with the resources of coopted systems, the more complex social-reasoning
capacities that are characteristic of humans emerge. As
a core system, impairments of ToM cannot be ameliorated by modifications to the structure of tasks, a finding
that arises from studies of children with autism. Autism
is a heterogeneous disorder72, and not all the people
who are diagnosed with autism fail ToM tasks.
However, for the many children with autism who do
fail, improvement in ToM performance does not occur
even with modifications of task structure, such as
explicit forms of test questioning73,74 (TABLE 1).
Implications for the emergence of ToM
The integrity of the circuitry of the amygdala system is a
necessary, but not a sufficient, condition for ToM, which
requires support from co-opted systems for its emergence. As with other innate abilities that are dependent
on early experience for their development, such as face
processing75, the environment must provide an adequate
set of data to trigger the capacity for ToM reasoning.
A probably vital element of this data set is early conversational experience that allows the child to gain access to
knowledge about the mental states of others at a time
when the neural substrates of co-opted systems such as
EF are maturing. Possible neural changes that accompany EF maturation include rapid growth in the right
frontal cortex38,76.
Exposure to conversational opportunities that allow
insight into mental states is central to socio-emotional
development77. With regard to ToM, such opportunities provide a powerful window on an accelerated maturational timetable, as ToM tasks can be solved by
most normal 4–5-year-old children in all cultures
studied so far78,79. Given the wide variation in conversational experience, these findings are consistent with the
idea that some minimal early access to knowledge of
mental states triggers ToM reasoning.
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Table 1 | Performance on ToM tasks
Study
Sample
Task performance*
Pass (%)
Fail (%)
Reference
n = 39
n = 26
n = 32
n = 58
83.0
65.4
75.9
65.5
17.0
34.6
24.1
34.5
84
85
83
74
83.3
87.5
16.7
12.5
56
58
28.6
71.4
74
3-year-olds
Joseph
Lewis & Osborne
Siegal & Beattie
Surian & Leslie
Patients with right-hemisphere damage
Siegal, Carrington & Radel
Surian & Siegal
n=6
n=8
People with autism (aged 7–18 years)
Surian & Leslie
n = 21
*Comparison of performance on theory of mind (ToM) tasks that use explicit forms of test questioning
— for example, “Where will the person with a false belief look first?” — in which 3-year-olds and
patients with right-hemisphere damage largely succeed, in contrast to people with autism.
Scholl and Leslie80,81 propose that developing performance on standard ToM tasks in children between the
ages of 3 and 4 years does not reflect a developing ToM,
but a developing selection processor (SP) mechanism
that is necessary for children to choose the correct
answer. At first, children have a very simple ToM that is
built on the premise that others’ beliefs correspond to
reality82. They need to inhibit this simple ToM and
shift attention to how beliefs can be false and do not
correspond to reality. Before the SP is in place, 3-year-old
children who respond incorrectly on standard tasks can
benefit, as do patients with right-hemisphere lesions, if
the test questions are designed to be temporally explicit,
such that subjects are unlikely to misinterpret the
purpose and relevance of the test questions58,83–85.
The SP might be particularly important as a mechanism in ToM reasoning. ToM tasks require the representation of invisible mental states, in contrast to the physical
representations that are required in analogous falsephotograph tasks, in which comparative ease of performance has been reported86. With the SP, children can
inhibit the canonical choice of reality that corresponds
to belief, and indicate that there will be a mismatch
between the two. They recognize that a story character
will initially be unable to find a desired object because
the believed location differs from reality.
Immersion in conversation is a spur for much of
this development. Conversational experience serves as a
gateway to others’ beliefs. It alerts children to the fact
that speakers are epistemic subjects who store and seek
to provide information about the world and, in doing
so, allow access to a world of referents and propositions
about intangible objects, creating the potential for
imagining past and future87.
Conclusion
The evidence that we have reviewed indicates that,
although performance on particular ToM tasks is supported by a widely distributed neural system, the functional components of which are co-opted for the
computation of mental states, at the core of ToM lies a
dedicated, domain-specific system. The impairment of
ToM reasoning can be traced to abnormalities in the
core system, which is centred on the amygdala circuitry,
NATURE REVIEWS | NEUROSCIENCE
as reflected by ToM disorders in many people with
autism. Similarly, impairments of ToM might result
from the failure of a co-opted system that is necessary
for performance on a particular set of tasks, as shown in
people with right-hemisphere lesions, or from the
absence of a trigger for the emergence of ToM, such as
conversational experience. For example, this experience
can be absent in deaf children, who respond to ToM
tasks in a similar manner to people with autism, but for
different reasons.
Deaf children of hearing parents who acquire a sign
language mainly outside the family and are therefore
‘late signers’ have the ability to attribute mental states
correctly in generating stories about others with whom
they have hypothetically interacted88. But even in
adolescence, such children, although competent in the
syntax of a sign language, have persistent difficulties on
ToM-reasoning tasks89, and the performance of late
signers is resistant to amelioration through changes to
the task structure48. In contrast to late signers, normal
children and ‘native signers’ — deaf children that are
born into families with a deaf parent who uses a sign
language — enjoy early conversational input that triggers the acquisition of our ability to interpret the
behavioural outcome of mental states on measures of
ToM reasoning (that is, our ability to recognize that
behaviour is determined by false beliefs rather than by
reality). These findings point to a critical period in
ToM. Just as children seem to be irreparably impaired
in their later language learning when not exposed at all
to an early language environment90–92, children require
at least some minimal access to conversation about
mental states to show ToM reasoning. Without such
access, they can be persistently impaired in appreciating that the minds of others contain a store of beliefs
that might differ from their own, and can be used to
predict and guide behaviour.
This perspective provides a framework for further
research on the emergence of ToM. Questions that arise
are amazingly rich and varied. For example, as shown
in a recent study of sequential cohorts of Nicaraguan
deaf children that were initially exposed to a highly
degraded language environment, children spontaneously create structures for language when acting
largely independently of adults93. Are deaf children who
are involved at an early stage in creating a language
more likely to succeed on ToM tasks than children who
have encountered a more rudimentary version of a sign
language when they are older? A second example concerns non-vocal children with cerebral palsy who, like
late signers, are liable to be isolated from conversation
about mental states that can trigger ToM reasoning94.
To what extent do such children have lingering ToM
impairments? A third example comes from deaf aphasia.
It is well established that deaf people with damage to
the left hemisphere are impaired in their use of sign
language, whereas deaf people with right damage are
impaired on visuo-spatial processing tasks95. A further
test of the independence of ToM reasoning from
language would involve comparisons of deaf patients
with right and left damage who were identified as
VOLUME 3 | JUNE 2002 | 4 6 9
REVIEWS
native or late signers before their injuries. To what
extent would ToM remain dissociated from language
impairments under these conditions?
ToM in the form of the person’s ability to interpret
mental states contributes substantially to building and
sustaining relationships with others. But the advantages
of ToM extend beyond social cognition. The ToM ability
to understand and predict the intentions of others is
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
470
Premack, D. & Woodruff, G. Does the chimpanzee have a
theory of mind? Behav. Brain Sci. 4, 515–526 (1978).
A classic article that shows the wide-ranging
significance of ToM, providing the impetus for crossspecies and human developmental research.
Suddendorf, T. & Whiten, A. Mental evolution and
development: evidence for secondary representation in
children, great apes, and other animals. Psychol. Bull. 127,
629–650 (2001).
Yurimiya, N., Erel, O., Sheked, M. & Solomonica-Levi, D.
Meta-analyses comparing theory of mind abilities of
individuals with autism, individuals with mental retardation,
and normally developing individuals. Psychol. Bull. 124,
283–307 (1998).
Wellman, H. M., Cross, D. & Watson, J. Meta-analyses of
theory-of-mind development. Child Dev. 72, 655–684
(2001).
Bloom, P. Language and thought: does grammar make us
smart? Curr. Biol. 10, R516–R517 (2000).
Frith, C. D. & Frith, U. Interacting minds — a biological basis.
Science 286, 1692–1695 (1999).
Frith, U. Mind blindness and the brain in autism. Neuron 32,
969–979 (2001).
Frith, U. & Frith, C. D. The biological basis of social
interaction. Curr. Dir. Psychol. Sci. 10, 151–155 (2001).
References 6–8 elegantly review the role of neural
systems that are involved in mentalizing, with
particular emphasis on the systems that underlie the
detection and interpretation of biological motion.
Leslie, A. M. in The New Cognitive Neurosciences 2nd edn
(ed. Gazzaniga, M. S.) 1235–1247 (MIT Press, Cambridge,
Massachusetts, 2000).
Varley, R. & Siegal, M. Evidence for cognition without
grammar from causal reasoning and ‘theory of mind’ in an
agrammatic aphasic patient. Curr. Biol. 10, 723–726 (2000).
Bloom, P. & German, T. Two reasons to abandon the false
belief task as a test of theory of mind. Cognition 77,
B25–B31 (2000).
A provocative and incisive examination of the
resources that are required to pass tests of ToM.
Astington, J. W. & Jenkins, J. M. A longitudinal study of the
relation between language and theory-of-mind
development. Dev. Psychol. 35, 1311–1320 (1999).
Carruthers, P. Language, Thought and Consciousness:
an Essay in Philosophical Psychology (Cambridge Univ.
Press, New York, 1996).
Plaut, D. C. & Karmiloff-Smith, A. Representational
development and theory-of-mind computations. Behav.
Brain Sci. 16, 70–71 (1993).
Smith, P. K. in Theories of Theory of Mind (eds Carruthers, P.
& Smith, P. K.) 344–354 (Cambridge Univ. Press, New York,
1996).
Tager-Flusberg, H. in Understanding Other Minds:
Perspectives from Developmental Cognitive Neuroscience
2nd edn (eds Baron-Cohen, S., Tager-Flusberg, H. &
Cohen, D. J.) 124–149 (Oxford Univ. Press, Oxford, UK,
2000).
de Villiers, J. G. & de Villiers, P. A. in Children’s Reasoning
and the Mind (eds Mitchell, P. & Riggs, K.) 191–228
(Psychology Press, Hove, UK, 2000).
Baron-Cohen, S. et al. Social intelligence in the normal and
autistic brain: an fMRI study. Eur. J. Neurosci. 11,
1891–1898 (1999).
Brunet, E., Sarfati, Y., Hardy-Bayle, M. C. & Decety, J. A PET
investigation of the attribution of intentions with a nonverbal
task. Neuroimage 11, 157–166 (2000).
Fletcher, P. C. et al. Other minds in the brain: a functional
imaging study of ‘theory of mind’ in story comprehension.
Cognition 57, 109–128 (1995).
Goel, V. et al. Modelling other minds. Neuroreport 6,
1741–1746 (1995).
Vogeley, K. et al. Mind reading: neural mechanisms of theory
of mind and self-perspective. Neuroimage 62, 89–106
(2001).
| JUNE 2002 | VOLUME 3
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
essential to learning in other domains, such as recognizing the meaning of words and adopting beliefs that are
specific to a culture96. Clearly, from the architecture of
core and co-opted systems, the human mind has the
capacity to marshal a series of mechanisms to develop
abilities such as ToM understanding and, to create from
this, more extended processing systems in which the
whole is greater than the sum of its parts.
References 18–22 present a series of state-of-the-art
functional imaging studies that have aimed to
elucidate the biological basis of ToM.
Iacoboni, M. et al. Cortical mechanisms of human imitation.
Science 286, 2526–2528 (1999).
Chaminade, T., Meltzoff, A. N. & Decety, J. Does the end
justify the means? A PET exploration of the mechanisms
involved in human imitation. Neuroimage 15, 318–328 (2002).
Gallese, V. & Goldman, A. Mirror neurons and the simulation
theory of mind-reading. Trends Cogn. Sci. 2, 493–501 (1998).
Rizzolatti, G., Fogassi, L. & Gallese, V. Neurophysiological
mechanisms underlying the understanding and imitation of
action. Nature Rev. Neurosci. 2, 661–670 (2001).
Leslie, A. M. & Frith, U. Autistic children’s understanding of
seeing, knowing and believing. Br. J. Dev. Psychol. 6,
315–324 (1988).
Perner, J., Frith, U., Leslie, A. M. & Leekam, S. R.
Exploration of the autistic child’s theory of mind: knowledge,
belief, and communication. Child Dev. 60, 689–700 (1989).
Van der Lely, H. K. J., Rosen, S. & McClelland, A. Evidence
for a grammar-specific deficit in children. Curr. Biol. 8,
1253–1258 (1998).
Custer, W. L. A comparison of young children’s
understanding of contradictory representations in pretense,
memory, and belief. Child Dev. 67, 678–688 (1996).
Lai, C. S. L. et al. A folkhead-domain gene is mutated in a
severe speech and language disorder. Nature 413, 519–523
(2001).
Hughes, C. & Cutting, A. L. Nature, nurture, and individual
differences in early understanding of mind. Psychol. Sci. 10,
429–432 (1999).
Hughes, C. & Plomin, R. in Evolution and the Human Mind:
Modularity, Language and Meta-Cognition (eds Carruthers,
P. & Chamberlain, A.) 47–61 (Cambridge Univ. Press, New
York, 2000).
Shallice, T. ‘Theory of mind’ and the prefrontal cortex. Brain
124, 247–248 (2001).
Carlson, S. M. & Moses, L. Individual differences in inhibitory
control and theory of mind. Cogn. Dev. 10, 483–527 (2001).
Frye, D., Zelazo, P. D. & Palfai, T. Theory of mind and rulebased reasoning. Cogn. Dev. 10, 483–527 (1995).
Perner, J. & Lang, B. Development of theory of mind and
executive control. Trends Cogn. Sci. 3, 337–344 (1999).
Stuss, D. T., Gallup, G. G. & Alexander, M. P. The frontal
lobes are necessary for ‘theory of mind’. Brain 124,
279–286 (2001).
An outstanding investigation of the performance of
patients with brain lesions on ToM tasks, which was
designed to compare the effects of frontal and
posterior damage in the left and right hemispheres.
Channon, S. & Crawford, S. The effects of anterior lesions
on performance on a story comprehension test: left anterior
impairment on a theory of mind-type task.
Neuropsychologica 38, 1006–1017 (2000).
Stone, V. E., Baron-Cohen, S. & Knight, R. T. Frontal lobe
contributions to theory of mind. J. Cogn. Neurosci. 10,
640–656 (1998).
Baron-Cohen, S. et al. Recognition of mental state terms:
clinical findings in children with autism and a functional
neuroimaging study of normal adults. Br. J. Psychiatry 165,
640–649 (1994).
Castelli, F., Frith, U., Happé, F. & Frith, C. Movement and
mind: a functional imaging study of perception and
interpretation of complex intentional movement patterns.
Neuroimage 12, 314–325 (2000).
Gallagher, H. et al. Reading the mind in cartoons and
stories: an fMRI study of ‘theory of mind’ in verbal and
nonverbal tasks. Neuropsychologia 38, 11–21 (2000).
Rowe, A. D. et al. ‘Theory of mind’ impairments and their
relationship to executive functioning following frontal lobe
excisions. Brain 124, 600–616 (2001).
Varley, R., Siegal, M. & Want, S. C. Severe grammatical
impairment does not preclude ‘theory of mind’. Neurocase
7, 489–493 (2001).
46. Heaton, R. K, Chelune, G. J., Talley, J. L., Kay, G. G. &
Curtiss, G. Wisconsin Card Sorting Test (Psychological
Assessment Resources, Odessa, Texas, 1993).
47. Peterson, C. C. & Siegal, M. Representing inner worlds:
theory of mind in autistic, deaf, and normal hearing children.
Psychol. Sci. 10, 126–129 (1999).
48. Woolfe, T., Want, S. C. & Siegal, M. Signposts to
development: theory of mind in deaf children. Child Dev. 73,
768–778 (2002).
49. Blakemore, S.-J. & Decety, J. From the perception of action
to the understanding of intention. Nature Rev. Neurosci. 2,
561–567 (2001).
50. Ruby, P. & Decety, J. Effect of subjective perspective taking
during simulation of action: a PET investigation of agency.
Nature Neurosci. 4, 546–550 (2001).
51. Fink, G. R. et al. The neural consequences of conflict between
intention and the senses. Brain 122, 497–512 (1999).
52. Jonides, J. et al. Spatial working memory in humans as
revealed by PET. Nature 363, 623–625 (1993).
53. Brownell, H., Happé, F., Blum, A. & Pincus, D. Distinguishing
lies from jokes: theory of mind deficits and discourse
interpretation in right hemisphere brain-damaged patients.
Brain Lang. 62, 310–321 (1998).
54. Weylman, S. T., Brownell, H. H., Roman, M. & Gardner, H.
Appreciation of indirect requests by left- and right-braindamaged patients: the effects of verbal context and
conventionality of wording. Brain Lang. 36, 580–591 (1989).
55. Moya, K. L., Benowitz, L. I., Levine, D. L. & Finklestein, S.
Covariant defects in visuospatial abilities and recall of verbal
narrative after right hemisphere stroke. Cortex 22, 381–397
(1986).
56. Siegal, M., Carrington, J. & Radel, M. Theory of mind and
pragmatic understanding following right hemisphere
damage. Brain Lang. 53, 40–50 (1996).
57. Happé, F., Brownell, H. & Winner, E. Acquired theory of mind
following stroke. Cognition 70, 211–240 (1999).
58. Surian, L. & Siegal, M. Sources of performance on theory of
mind tasks in right hemisphere damaged patients.
Brain Lang. 78, 224–232 (2001).
References 53–58 provide cumulative evidence
for the cognitive and communicative impairments that
are associated with damage to the right hemisphere.
59. Rutter, M. Diagnosis and definition of childhood autism.
J. Autism Child. Schizophr. 8, 139–161 (1978).
60. Wing, L. in Diagnosis and Treatment of Autism (ed.
Gillberg, C.) 5–22 (Plenum, New York, 1989).
61. Brothers, L. The social brain: a project for integrating primate
behaviour and neurophysiology in a new domain. Concepts
Neurosci. 1, 27–51 (1990).
62. Adolphs, R. Social cognition and the human brain.
Trends Cogn. Sci. 3, 469–479 (1999).
63. Baron-Cohen, S. et al. The amygdala theory of autism.
Neurosci. Biobehav. Rev. 24, 355–364 (2000).
64. Abell, F. et al. The neuroanatomy of autism: a voxel-based
whole brain analysis of structural scans. Neuroreport 10,
1647–1651 (1999).
65. Kemper, T. L. & Bauman, M. L. The contribution of
neuropathologic studies to the understanding of autism.
Neurol. Clin. 11, 175–187 (1993).
66. Happé, F. et al. ‘Theory of mind’ in the brain: evidence from
a PET scan study of Asperger syndrome. Neuroreport 8,
197–201 (1996).
67. Howard, M. A. et al. Convergent neuroanatomical and
behavioral evidence of an amygdala hypothesis of autism.
Neuroreport 11, 2931–2935 (2000).
68. Carper, R. A. & Courchesne, E. Inverse correlation between
frontal lobe and cerebellum sizes in children with autism.
Brain 123, 836–844 (2000).
69. Bachevalier, J. Medial temporal lobe structures and autism:
a review of clinical and experimental findings.
Neuropsychologia 32, 627–648 (1994).
An influential review of the biological basis of autism.
70. Bachevalier, J., Malkova, L. & Mishkin, M. Effects of selective
neonatal temporal lobes on socioemotional behavior in
www.nature.com/reviews/neuro
REVIEWS
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
infant rhesus monkeys (Macaca mulatta). Behav. Neurosci.
115, 545–559 (2001).
Prather, M. D. et al. Increased social fear and decreased fear
of objects in monkeys with neonatal amygdala lesions.
Neuroscience 106, 653–658 (2001).
Lord, C., Cook, E. H., Leventhal, B. L. & Amaral, D. G.
Autism spectrum disorders. Neuron 28, 355–363 (2000).
Roth, D. & Leslie, A. M. Solving belief problems: toward a
task analysis. Cognition 66, 1–31 (1998).
Surian, L. & Leslie, A. M. Competence and performance in
false belief understanding: a comparison of autistic and
normal 3-year-old children. Br. J. Dev. Psychol. 17, 141–155
(1999).
Le Grand, R., Mondloch, C. J., Maurer, D. & Brent, H. P.
Neuroperception: early visual experience and face
processing. Nature 410, 890 (2001).
Reports that infants with cataracts that are removed
at 2–6 months of age remain impaired in their
recognition of faces even after 9 years or more of
visual experience — a convincing demonstration of
the importance of critical periods in early human
development.
Thatcher, R. W. Cyclic cortical organization during early
childhood. Brain Cogn. 20, 24–50 (1992).
Peterson, C. C. Kindred spirits: influences of siblings’
perspectives on theory of mind. Cogn. Dev. 15, 435–455
(2001).
Avis, J. & Harris, P. L. Belief–desire reasoning among Baka
children: evidence for a universal conception of mind. Child
Dev. 62, 460–467 (1991).
Lee, K., Olson, D. R. & Torrance, N. Chinese children’s
understanding of false beliefs: the role of language. J. Child
Lang. 26, 1–21 (1999).
Scholl, B. & Leslie, A. M. Modularity, development and
theory of mind. Mind Lang. 14, 131–153 (1999).
Scholl, B. & Leslie, A. M. Minds, modules, and metaanalysis. Child Dev. 72, 131–153 (2001).
Fodor, J. A. A theory of the child’s theory of mind. Cognition
44, 283–296 (1992).
Siegal, M. & Beattie, K. Where to look first for children’s
knowledge of false beliefs. Cognition 38, 1–12 (1991).
NATURE REVIEWS | NEUROSCIENCE
84. Joseph, R. M. Intention and knowledge in preschoolers’
conception of pretend. Child Dev. 69, 966–980 (1998).
85. Lewis, C. & Osborne, A. Three-year-olds’ problems with
false belief: conceptual deficit or linguistic artifact? Child Dev.
61, 1514–1519 (1990).
86. Slaughter, V. Children’s understanding of pictorial and
mental representations. Child Dev. 69, 321–332 (1998).
87. Harris, P. L. in Theories of Theory of Mind (eds Carruthers, P.
& Smith, P. K.) 200–220 (Cambridge Univ. Press, New York,
1996).
A powerful statement on the role of language and
access to conversational experience in ToM
understanding.
88. Marschark, M., Green, V., Hindmarsh, G. & Walker, S.
Understanding theory of mind in children who are deaf.
J. Child Psychol. Psychiatry 41, 1067–1073 (2000).
89. Russell, P. A. et al. The development of theory of mind in
deaf children. J. Child Psychol. Psychiatry 39, 903–910
(1998).
90. Curtis, S. Genie: a Psycholinguistic Study of a Modern-Day
‘Wild Child’ (Academic, New York, 1977).
91. Grimshaw, G. M., Adelstein, A., Bryden, M. P. & MacKinnon,
G. E. First-language acquisition in adolescence: evidence for
a critical period for verbal language development. Brain Lang.
63, 237–255 (1998).
92. Lenneberg, E. H. Biological Foundations of Language
(Wiley, New York, 1967).
93. Senghas, A. & Coppola, M. Children creating language: how
Nicaraguan sign language acquired a spatial grammar.
Psychol. Sci. 12, 323–328 (2001).
94. Dahlgren, S., Dahlgren Sandberg, A. & Hjelmquist, E. The
nonspecificity of theory of mind deficits: evidence from
children with communicative disabilities. Eur. J. Cogn.
Psychol. (in the press).
A recent pioneering exploration of the extent of ToM
deficits in children with various communicative
impairments, focusing on the performance of nonvocal children with cerebral palsy.
95. Hickok, G., Belugi, U. & Klima, E. S. The neural organization
of language: evidence from sign language aphasia. Trends
Cogn. Sci. 2, 129–136 (1998).
96. Bloom, P. How Children Learn the Meaning of Words
(MIT Press, Cambridge, Massachusetts, 2000).
97. Wimmer, H. & Perner, J. Beliefs about beliefs: representation
and constraining function of wrong beliefs in young children’s
understanding of deception. Cognition 13, 103–128 (1983).
98. Baron-Cohen, S., Leslie, A. M. & Frith, U. Does the autistic
child have theory of mind? Cognition 21, 37–46 (1985).
99. Head, H. Aphasia and Kindred Disorders of Speech
(Cambridge Univ. Press, London, 1926).
100. Hughlings Jackson, J. in Selected Writings of John Hughlings
Vol. 2 (Staples, London, 1958; originally published 1866)
101. Marie, P. in Pierre Marie’s Papers on Speech Disorders
(eds Cole, M. F. & Cole, M.) (Hafner, New York, 1906).
102. Kertesz, A. in Thought without Language (ed. Weiskrantz,
L.) 451–463 (Oxford Univ. Press, Oxford, UK, 1988).
103. Varley, R. in The Cognitive Basis of Science (eds Carruthers,
P., Stich, S. & Siegal, M.) 99–116 (Cambridge Univ. Press,
New York, 2002).
Acknowledgements
We are grateful to S. Laurence, O. Pascalis and L. Surian for their
comments on an earlier version of this article. For their valuable
input, we also thank members of the Innateness and the Structure
of the Mind project, which is sponsored by the Arts and Humanities
Research Board (UK). The Leverhulme Trust and the Nuffield
Foundation provided generous support that is reflected in the
research reviewed here.
Online links
FURTHER INFORMATION
Encyclopedia of Life Sciences: http://www.els.net/
autism | brain imaging: localization of brain functions | brain
imaging: observing ongoing neural activity | language | magnetic
resonance imaging
MIT Encyclopedia of Cognitive Sciences:
http://cognet.mit.edu/MITECS/
autism | cognitive development | magnetic resonance imaging |
positron emission tomography | theory of mind
Access to this interactive links box is free online.
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