Evolutionary Developmental Psychopathology

How to Proceed with the Investigation and Classification of Disorders
If we accept that our current schemes of classification are not only an unreliable guide to the nature of psychopathology, but an impediment to investigation, how are we to extract anything of value from the vast literature in psychiatry, psychology and related fields? First of all, we should adopt the theory driven approach of evolutionary developmental psychopathology, which will help us to interpret and synthesize existing findings, if the assumptions outlined so far are broadly correct, and above all we should remember that adaptations were forged to function in past environments and not necessarily in our current environment. Secondly, we should include in our investigations brain-damaged patients (who are often excluded from current research) as an analysis of pathology will help us to map psychological functions on to brain systems (Frith, 1992, p. 8). Thirdly, we should investigate not only behavioural abnormalities but information-processing abnormalities, in a scheme that acknowledges both cognition and affect as components of information processing. Fourthly, we should concentrate our investigations on specific signs and symptoms, rather than syndromes, as symptoms such as delusions and hallucinations, for example, are observed in patients who currently fall into a number of categories, including schizophrenia and affective psychosis (Frith, 1992, p. 9). Fifthly, we should expect that complex psychological processes should be broken down into simpler tasks that can be performed by the mindless agents in our ‘society of mind’. Finally, we should be particularly attentive to any data showing sexual dimorphism and changes in psychological functioning and neural architecture across the lifespan, and to comparisons between adults, adolescents, and children. The remainder of this chapter will examine the applicability of this framework to existing findings in psychopathology. Although the evolutionary approach should inform the whole of psychopathology I will concentrate on those findings that illustrate most vividly the ideas discussed so far. I will also suggest a number of original hypotheses that enable us to integrate results from a range of research.
The Theory of Mind Module and Psychopathology
Perhaps our most distinctive attribute is the capacity to manage highly complex social interactions. As Sanjida O’Connell explains ‘we do not interact with other people by looking at how they behave, rather, we think about what they are thinking and respond to them on that basis’ (1997, p. 2). How do we establish reciprocal relationships, avoid (or initiate) confrontations, find mates, and establish our social roles? How does our capacity to engage in these activities develop and change over the lifespan? Does the development of social cognition relate to the changing balance between the need to allocate resources to survival, development, and reproduction? Using Tinbergen’s framework we should ask: what are the mechanisms of social intelligence? How do they develop? How do they function? How did they evolve? When we are equipped with a knowledge of the mechanisms of social intelligence we will be better placed to investigate the nature and causes of its dysfunction as this relates to psychopathology.

Working within the modular framework Simon Baron-Cohen (1995) has elaborated a model of the evolution and development of ‘mindreading’. Baron-Cohen argues that we automatically and often unconsciously interpret human behaviour in terms of beliefs, desires and intentions through the operation of the adaptive cognitive mechanisms comprising the theory of mind module, and that children with autism (Kanner, 1943) suffer from ‘mindblindness’ as a result of an impairment of this module. The theory of mind module, or mindreading mechanism, is also referred to as a component of ‘Machiavellian intelligence’ (Byrne & Whiten, 1997; 1988) or social cognition (Adolphs, 1999). Baron-Cohen identifies four different mechanisms comprising the human mindreading system, the Intentionality Detector (ID), the Eye Direction Detector (EDD), the Shared Attention Mechanism (SAM) and the Theory of Mind Module (ToMM). These components roughly reflect four properties of the natural environment: volition, perception, shared attention and epistemic states.

The Intentionality Detector
The first component of the mindreading system is ID, the Intentionality Detector. This is ‘a perceptual device that interprets motion stimuli in terms of goal and desire’ (Baron-Cohen, 1995, p. 32) and which preferentially attends to stimuli exhibiting self-propulsion and direction. This most basic component of mindreading can take input from any modality (vision, touch, audition etc.) and from stimuli with hugely differing morphology and structure. It is, therefore, as easy for us to attribute intentionality to an insect, or a cow, as it is to a human being, and for us to mistakenly attribute intentionality, albeit briefly, to such things as pieces of paper blowing in the wind, or to collections of pixels making up computer sprites. The amodal property of ID is apparent in our capacity to attribute intentionality to tactile, auditory and other stimuli. Even young infants are sensitive to changes in an adult’s goal, for example, they respond to the distinction between a give and a tease (Reddy, 1991). In a classic study adults were found to explain the movement of geometrical shapes in a short film in terms of goals (Heider & Simmel, 1944), and this result has been repeated with children (Dasser, Ulbaek & Premack, 1989).
The Eye Direction Detector
This perceptual device has three basic functions: ‘it detects the presence of eyes or eye-like stimuli, it computes whether eyes are directed toward it or toward something else, and it infers from its own case that if another organism’s eyes are directed at something then that organism sees that thing’ (Baron-Cohen, 1995, pp. 38-39). Both ID and EDD form dyadic representations, in the case of ID representations involving goal and desire (‘Her goal is to go over there’, ‘It wants to get the cheese’), in the case of EDD those representations involving visual perception (‘It sees me’, ‘Mummy sees the door’). These representations are termed dyadic because they describe intentional, or mentalistic, relations between two objects, either Agent and Object, or Agent and Self, and the mechanisms underlying them form the basis of an autistic universe, one in which agents and objects and the relations between them can be observed, but in which these observations do not form the basis of shared attention, which is the domain of a third component of the mindreading system. Both ID and EDD provide input for this third mechanism, the Shared Attention Mechanism.
The Shared Attention Mechanism
The function of the Shared Attention Mechanism is to form triadic representations, which is the representation of a triadic relation. Triadic representations specify the relations among an Agent, the Self and an Object (or another Agent) and can be expressed in the following form:
[Agent/Self-Relation-(Self/Agent-Relation-Proposition)]
For example,
[Mummy-sees-(I-see-the bus)]
These examples are taken from Baron-Cohen who notes that ‘this attempt at formalism is useful because it brings out that a triadic representation contains an embedded dyadic representation’ (Baron-Cohen, 1995, p. 45). SAM is like a comparator in that it can fuse ‘dyadic representations about another’s current perceptual state and dyadic representations about the self’s current perceptual state into a triadic representation’ (Baron-Cohen, 1995, p. 46). SAM has a privileged relationship with EDD in that triadic representations are generally formed through the perception of eye direction, but SAM also makes the input from ID available to EDD so that eye direction can be read in terms of an agent’s goals or desires.
The Theory-of-Mind Mechanism or Module (ToMM) was first proposed by Alan Leslie (1994) as a system for inferring the full range of mental states from behaviour and has been adopted by Baron-Cohen, who notes that
…the other three mechanisms have got us to the point of being able to read behaviour in terms of volitional mental states (desire and goal) and to read eye direction in terms of perceptual mental states (e.g., see). They have also got us to the point of being able to verify that different people can be experiencing these particular mental states about the same object or event (shared attention). But a theory of mind, of course, includes much more. (Baron-Cohen, 1995, p. 51).
In particular we need two additional things: the capacity to represent the complete range of epistemic mental states, and ‘a way of tying together all of the mental-state concepts (the perceptual, the volitional and the epistemic) into a coherent understanding of how mental states and actions are related’ (Baron-Cohen, 1995, p. 51). One of these requirements, that of representing epistemic mental states, is achieved through ToMM’s capacity to form M-Representations. These are representations of propositional attitudes that take the form:
[Agent-Attitude-‘Proposition’]
For example,
[Ian-believes-‘it is raining’]
ToMM may begin to emerge between 18 and 24 months as this period generally marks the onset of pretend play and

…infants become able to construe the behaviour of other Agents as relating to fictional states of affairs, specifically, as issuing from the attitude of pretending the truth of a proposition that describes a fictional state of affairs. For example, a mother’s actual behaviour of talking to a banana can be understood by constructing the M-representation, mother pretends (of) the banana (that it is true that) ‘it is a telephone’. This links her behaviour, via an attitude, to a fiction (Leslie, 1994, p. 141, emphasis in the original).

It is important to note that through M-representations ToMM can confer a key property of epistemic states, that of referential opacity (or non-substitutability) thus suspending the normal truth relations of propositions. Leslie explains:
…the reference of terms in such embedded propositions becomes opaque (Quine, 1961). For example, “the prime minister of Britain” and “Mrs. Thatcher” refer at this time of writing to the same person. Therefore, anything asserted about the prime minister of Britain, if true, must be true of Mrs. Thatcher as well (and, likewise, false for one, false for the other). If it is true that the prime minister of Britain lives at No. 10 Downing Street, then it must be true that Mrs. Thatcher lives at No. 10 Downing Street. But put this proposition in the context of a mental state term and this no longer holds. Thus, “Sarah-Jane believes that the prime minister of Britain lives at No. 10 Downing Street” in no way entails the truth (or falsehood) of “Sarah-Jane believes Mrs. Thatcher lives at No. 10 Downing Street”. In a mental state context one can no longer “look through” terms to see what they refer to in deciding such issues. The mental state term suspends normal reference relations. Quine (1961) called this referential opacity (Leslie, 1987, p. 416).
Hence the statement ‘Snow White thought the woman selling apples was a kind person’ can be true, while ‘Snow White thought her wicked stepmother was a kind person’ may be false (Baron-Cohen, 1995, p. 53).
Tying the Four Mindreading Mechanisms Together
Baron-Cohen suggests that ToMM receives inputs from ID and EDD via SAM because SAM’s triadic representations have a relation slot that can take attitude terms and thereby be converted into M-representations.
Triadic representation: [Agent/Self-Relation-(Self/Agent-Relation-Proposition)]

M-representation: [Agent-Attitude-“Proposition”]

Therefore ToMM cannot develop without a functioning shared attention mechanism. The ontogeny of these mechanisms can be summarised as follows (Baron-Cohen, 1995):

Phase	Mechanism	Age	Representations
I ‘Primary Intersubjectivity’	ID Basic functions of EDD	Birth to 9 months	Dyadic
II ‘Secondary Intersubjectivity’	SAM	9 to 18 months	Triadic
III	ToMM	18 to 48 months	M-representations