Running head: NEUROBIOLOGY OF THEORY OF MIND by 8P6Cqm4

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Running head: NEUROBIOLOGY OF THEORY OF MIND




   Understanding the Development of Theory of Mind: Contributions from Neurobiology

                                      HDP 3286
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     Understanding the Development of Theory of Mind: Contributions from Neurobiology

      When the term was first used by Premack and Woodruff (1978), theory of mind was meant

to refer to the ability of attributing mental states to others in order to make inferences about their

behaviour. Since that time, the definition of theory of mind has undergone considerable change

and the conceptualization of theory of mind development has been largely debated amongst

psychologists (Astington, 2006).      In one camp, researchers have argued for a modular, or

domain-specific, account of theory mind (Frith & Frith, 1999; Saxe & Powell, 2006). Within

this view, theory of mind is an innate psychological structure that develops independently and

has evolved specifically to deal with issues of human social functioning. Alternatively, other

researchers have argued that theory of mind is an integrated construct that incorporates domain

general abilities such as executive function and language (Milligan, Astington, & Dack, 2007;

Apperly, Samson, Chiavarino, Bickerton, & Humphreys, 2007). According to this constructivist

framework, the development of theory of mind is largely influenced by the concurrent

development of associated cognitive abilities and is, therefore, more variable in its expression

and underlying structure. Importantly, proponents of this latter approach do not believe that

theory of mind understanding necessitates the development of a domain-specific mechanism

(Stone & Gerrans, 2006).       Thanks to recent advancements in the field of developmental

neuroscience, a potential resolution to this debate might be found through neurological mappings

of social cognitive functions. The purpose of this paper will be to review current neurological

evidence in an effort to assess the validity of each account. Specifically, this paper will address

whether (a) theory of mind understanding arises from the development of neurological structures

that are specialized to respond to the processing of mental states, or (b) theory of mind
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understanding arises from the integration of multiple structures that are associated with the

domain-general ability of metarepresentation.                                                          Comment [c1]: Very nice writing: eloquent and
                                                                                                       precise.

Evidence in Support of a Modular Approach

      Proponents of a modular account for theory of mind believe that a domain-specific

mechanism is primarily responsible for the attribution and understanding of mental states.

Evidence in support of this account has traditionally come from research examining the false

belief understanding – i.e., understanding that the mental states of others can contradict a current

state of reality – of typical and atypical populations (Leslie & Thaiss, 1992; Saxe & Baron-

Cohen, 2006). Specifically, research has shown that individuals can have unique deficits in false

belief understanding while still demonstrating a normal range of functioning on similar tasks that

do not require the metarepresentation of mental states (Leslie & Thaiss, 1992). The existence of

selective deficits in mental state understanding has consequently led certain researchers to

hypothesize the existence of brain structures that are selectively engaged in the processing of

mental states. Importantly, proponents of this view maintain that structures associated with

theory of mind understanding should show unique patterns of activation during the processing of

mental state representations and should be less active during processing of non-mental state

representations (Saxe & Baron-Cohen, 2006).

      Through the use of brain imaging technology, researchers have recently begun to test the

modular account directly and identify brain regions that appear to be closely associated with

theory of mind understanding. These regions include the right and left temporo-parietal junction

and the posterior cingulate (Frith & Frith, 1999; Saxe & Powell, 2006; Sabbagh & Taylor, 2000).

The most consistent findings to date, however, have been for the selective activation of the right

temporo-parietal junction during the processing of false belief tasks (Perner, Aichhorn,
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Kronbichler, Staffen, & Laudurner, 2006; Saxe & Powell, 2006). In these studies, researchers

have shown that activation of the right temporo-parietal junction may be selectively associated

with the processing of mental-state perspectives but not with more domain-general types of

metarepresentation. For example, in a study conducted by Perner and colleagues (2006), fMRI

images were obtained for adult participants who read and answered questions related to three

similar metarepresentation scenarios: false beliefs, false signs, and false photographs.

Importantly, the scenarios were designed so that participants would only have to consider the

mental state of others when answering a question related to a false belief (e.g., a tourist who

incorrectly believes the location of a landmark after being given false directions) but not when

interpreting a false sign (e.g., a road sign indicating the wrong direction) or a false photograph

(e.g. a dated photograph of a scene that has since changed). Thus, the researchers were able to

distinguish neural activation patterns that were uniquely associated with the metarepresentation

of mental vs. non-mental states.      In their results, Perner and colleagues found that while

activation in the left temporo-parietal junction (TPJ-L) did not distinguish between processing of

false beliefs and false signs, activation in the right temporo-parietal junction (TPJ-R) was

significantly greater during the processing of false beliefs than during the processing of the other

two scenerios. The authors consequently concluded that the TPJ-R may be uniquely associated

with the metarepresentation of mental states and may therefore be a good candidate for a theory

of mind “module”. Similar findings were also obtained by Saxe and Powell (2006), who found

that the TPJ-R was selectively activated when participants were asked to read descriptions of a

protagonist’s thoughts or beliefs but not when they read about a protagonist’s appearance or

subjective physical feelings (e.g., hunger).
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     Taken together, the above studies lend strong support for to the modular account of theory

of mind. By demonstrating that the right temporo-parietal junction is selectively activated when

an individual processes the thoughts or beliefs of another person, the current evidence suggests

that certain regions of the human brain do develop to specialize in theory of mind understanding.

Importantly, the fact that the TPJ-R does not show a similar pattern of activation during the

processing of non-mental state representations further supports the unique specialization of this

region.                                                                                               Comment [c2]: Very carefully worded. Clear and
                                                                                                      concise.

Evidence in Support of a Constructivist Approach

     From a constructivist framework, theory of mind understanding is a specialized cognitive

construct that arises from the integration of various domain-general processes. As a result,

proponents of this account do not believe that the development of theory of mind requires the

functional specialization of brain regions (Stone & Gerrans, 2006). Instead, theorists in this

camp believe that neurological structures associated with theory of mind understanding may also

be recruited for the processing of non-mental states. As proposed by Stone and Gerrans (2006),

theory of mind understanding does not necessitate a domain-specific mechanism because it can

more parsimoniously be accounted for by the integration of related social functioning abilities.

     To date, much of the evidence in support of this account has demonstrated that that theory

of mind abilities are in fact associated with highly integrated networks of neural activation (Abu-

Akel, 2003). Specifically, studies have shown that theory of mind understanding often requires

the activation of structures that are not uniquely associated with false belief understanding (Abu-

Akel, 2003; Apperly et al., 2007; Stone & Gerrans, 2006).          For example, damage to the

amygdala has been shown to be associated with impairments in social understanding (Abu-Akel,

2003).    Activation of the orbitofrontal cortex and medial prefrontal cortex has also been           Comment [c3]: ….and damage to my tires slows
                                                                                                      down my car, but I would not say that my tires are
                                                                                                      part of a network that makes my car go fast….this
                                                                                                      kind of logic makes me shudder…
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associated with the processing of mental states (Baron-Cohen, Ring, Moriarty, Schmitz, Costa &

Ell, 1994; Stuss, Gallup, & Alexander, 2001). Thus, regions of the brain that are typically

associated with more general processing of social input also appear to be important for the

understanding of theory of mind.                                                                        Comment [c4]: But your review is nice and clear.


      Recently, research with brain damaged patients has also brought into question the domain-

specificity of certain neurological structures associated with theory of mind understanding.

Specifically, a study conducted by Apperly and colleagues (2004) demonstrated that patients

with damage to the left temporo-parietal junction (TPJ-L) were selectively impaired on false

belief tasks. This evidence contradicts Perner and colleagues’ (2006) research which shows that

activation of the right temporo-parietal junction, as opposed to the left, selectively differentiated

between the processing of mental state and non-mental state representations. Moreover, in a

follow-up study conducted by Apperly and colleagues (2007), results indicated that patients who

had previously shown selectively selective deficits in false belief understanding also showed

deficits in reasoning about non-mental state representations (i.e., false photographs).         This

research, therefore, suggests that similar neural pathways are recruited for the metarepresentation

of mental and non-mental states. Importantly, it also suggests that the TPJ-R may not be as

uniquely associated with theory of mind understanding as others have argued.

      In the end, although regions have been identified that are uniquely associated with mental

state reasoning, most theory of mind tasks appear to require the integrative activation of several

brain regions.

                                            Discussion

Summary of Evidence: Modular vs. Constructivist Accounts
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     In the current paper, neurological evidence in support of both modular and constructivist

accounts of theory of mind were reviewed in an effort to resolve the structural nature of theory of

mind development. Specifically, this paper sought to address whether the ability to reason about

mental states is dependent on: (a) the development of highly specialized neural structures, or (b)

the formation of pathways between structures that are associated with domain-general functions.

Based on the current evidence, it appears as if there is strong support for the existence of

structures that are specialized to deal with theory of mind understanding (Saxe & Powell, 2006;

Perner et al., 2006). Although several studies have also shown that mental state reasoning is

associated with an integrated set of domain-general structures (e.g., medial prefrontal cortex),

evidence supporting the specialized role of the right temporo-parietal junction cannot be readily

dismissed. As such, the current evidence seems to suggest that theory of mind understanding is

dependent on both specialized and domain-general structures in the brain. What is currently less

clear, however, is whether the specialization of neural structures in the adult brain provides

unequivocally support for the modular development of theory of mind in young children. As

will be discussed in the following section, there are many problems inherent in making this

assumption. Based on recent models of neural development (Johnson, 2000; Karmiloff-Smith,

2007), it may also be possible to account for the development of domain-specific structures using

a constructivist perspective. In the final section of this discussion, an alternate model of theory

of mind development will be proposed based on the principles of probabilistic epigenesis – i.e., a

developmental framework that emphasizes the dynamic interactions between function and

structure (Johnson, 2000; Karmiloff-Smith, 2007).

Critique of the Modular Account
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     While the evidence in support of a modular account of theory of mind is compelling, it is

problematic to assume that the development of highly specialized neural structures is equally

specialized, or predetermined.    In her framework of atypical neural development, Annette           Comment [c5]: …otherwise, tautological


Karmiloff-Smith (2007) argues that by focussing on adult imaging data, researchers often fall

into the trap of assuming the specialized neural functions arise from innate and localized neural

development. Similarly, researchers may ignore the important functional changes that can occur

in neural structures over time because most of these changes would have occurred by the time

images are captured in adulthood. As such, structures that can appear domain-specific, or

“modular”, in adulthood may in fact originate from less localized patterns of activation during

childhood (Johnson, 2000; Karmiloff-Smith, 2007). This argument would certainly apply to the

imaging studies reviewed in the current paper as all this research was conducted with adult

populations. Although largely due to the limitations of current imaging technology, no study to

date has examined the neural structures associated with children’s theory of mind understanding.

Given that children begin to show sign of mental state awareness by 18-months (Frith and Frith,

1999) but do not typically acquire false belief understanding until the age of four-years

(Astington, 2006; Saxe & Baron-Cohen, 2006), it is unlikely that the neural activation patterns of

young children would appear as highly localized as those in adults.                                  Comment [c6]: ….well, that’s a strange
                                                                                                     argument. Even though my boys didn’t walk very
                                                                                                     well at 1 year, their feet were already highly
     As an alternative to the modular account of neural development, Annette Karmiloff-Smith         specialized. In other words, a delay in the onset of a
                                                                                                     function doesn’t, in itself, imply distributed or
                                                                                                     emergent structure. But I do see your larger point,
(2007) and Mark Johnson (2000) offer an alternate account of neural specialization that is based     and I think it’s great that you’ve utilized the
                                                                                                     Johnson/ K-S approach here.
on the framework of probabilistic epigensis. Specifically, these researchers propose that the

localization of psychological functions is determined by the dynamic interaction between

genetics, neural maturation, and functional input. Early in development, few brain regions are

specialized to process specific types of information. Instead, different regions or pathways,
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“compete” for the processing of different inputs and genetic biases ensure that certain neural

pathways are better suited to process certain types of information (e.g., neurons in the occipital

lobe may be biased to process visual stimuli). Through a process of natural selection, certain

pathways eventually become more effective at processing specific types of input and less

effective pathways are pruned, or cease to respond to the same input (Johnson, 2000; Karmiloff-

Smith, 2007). Thus, neural patterns of activation become more selective and psychological

functions become more efficient. What is unique about this approach is that it allows for the

“partial operation” of psychological functions that have yet to develop more specialized patterns

of activation (Johnson, 2000). Importantly, it also allows for highly specialized functions, such

as theory of mind, to be temporarily processed by less specialized pathways in the brain

(Karmiloff-Smith, 2007).                                                                             Comment [c7]: Beautiful! You understand and
                                                                                                     express this approach very well!

Applying Probabilistic Epigenesis to Theory of Mind Development

     Using the frameworks proposed by Mark Johnson (2000) and Annette Karmiloff-Smith

(2007), it is possible to propose an alternate account of theory of mind development that

incorporates the evidence for both modular and constructivist approaches. First, this model

would have to explain the discrepancies found the localization of mental state reasoning

functions (Apperly, Samson, Chaivarino, & Humphreys, 2004; Perner et al., 2006). Second, this

model would have to explain why theory of mind understanding would require both the

specialization of neural structures and the recruitment of domain-general neural pathways.

     With regards to the first point, this framework would predict that the localization of theory

of mind functions would be open to a certain degree of variance due to the variability of

individual social experiences. Thus, individuals who receive atypical social input, either because

of atypical development or brain damage, may consequently develop distinct patterns of
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localization for the processing of theory of mind. Similarly, this framework would predict that

individuals raised in an environment that demands increased amounts of mental-state reasoning

(e.g., a daycare where children are engaged in vast amounts of social interaction) might show

earlier patterns of localization as a result of their environmental input.

      With regards to the second point, this model would predict that before psychological

functions become fully localized in the brain, they can be temporarily executed by less

specialized neural pathways. In the case of theory of mind, these less specialized structures may

include regions of the limbic and paralimbic pathways that are associated with the processing of

social input (Abu-Akel, 2003). As certain regions gain specialization in the processing of mental

states, less specialized regions may still be recruited during the processing of mental states

because they assist with the domain-general demands of a given task.                                Comment [c8]: Yes, but the main point is that
                                                                                                    these less specialized regions should become less
                                                                                                    active with development, as a small number of
      In the end, the application of probabilistic epigenesis to theory of mind understanding       structures “out-bid” the rest. Or, to put it differently,
                                                                                                    for most children, there would be a normative
                                                                                                    progression of increasing specialization. But you’re
makes it possible to account for the development of domain-specific structures without having to    right: the less specialized regions would still be part
                                                                                                    of the larger network, and that would explain the
                                                                                                    findings which appear to support the constructivist
make assumptions about the modularity of brain structures.                                          account.
                                                                                                    Comment [c9]: Absolutely right.
Conclusions

      Recent findings from adult imaging studies has have provided strong evidence for the

localization of mental state reasoning in the brain. Although the existence of highly specialized

structures may provide some support for modular accounts of theory of mind development,

recent models of neural development raise some doubts to this conclusion. Alternatively, a

model of theory of mind development based on the principles of probabilistic epigenesis may

offer a more comprehensive description explanation, not description of the current neurological

evidence. Specifically, this model can account for potential discrepancies in the functional

localization of mental state reasoning. In addition, this model can account for the simultaneous
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recruitment of highly specialized and domain-general pathways during the processing of mental

state representations.




Comments:


This was a very fine piece of work. I’m impressed! Your review of the evidence was clear

and articulate and you framed the debate with insight as well as precision. You captured

the gist of the argument with exquisite balance, as well as economy of writing, and you

spelled out each side’s contentions precisely as well as concisely. But then you actually

introduced a fresh vantage point which was capable of resolving the discrepancies in the

data, by applying an intrinsically developmental formula to the problem. You showed how

specialization might emerge, rather than being programmed in, through selectionist

processes, so that specialized structures might show up against a background of more

domain-general structures. This argument could have used further refinement and

development, but the point of it was completely valid and justified. And your use of the

Johnson model to tackle this particular problem was absolutely original, as far as I know.

In fact, this degree of original problem solving in a domain which is not your home turf is

really something to be proud of. It is probably the only approach that could actually

resolve the debate without undermining either side. This was a rare treat in a term paper.

Excellent job!


Paper: A+
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