STUDIES OF THEORY OF MIND: Are Intuitive Physics and Intuitive Psychology Independent?

According to the framework of evolutionary psychology, the human mind should be considered in terms of its evolved adaptedness to the environment (KarmiloffSmith, Grant, Bellugi & Baron-Cohen, 1995). Two postulated neurocognitive adaptations are intuitive (or folk) psychology, for inferring social causality; and intuitive (or folk) physics, for inferring physical causality. In this paper we test these two aspects of our causal cognition in children with Asperger Syndrome (AS). To do this, we employ new tests of intuitive physics and intuitive psychology. Results show that children with AS are impaired in folk psychology whilst being superior in folk physics. Future work needs to test if intuitive psychology and physics are truly independent of one another (implying separate underlying mechanisms) or are inversely related to one another (implying a single underlying mechanism for both). The Evolutionary Framework The model guiding this study holds that there are specialized neurocognitive mechanisms that have evolved to enable rapid discrimination of two classes of entity: agents vs. non-agents (Baron-Cohen, 1994; Leslie, 1995; Premack, 1990). This follows from the classical view that in this universe there are only two 47 Acknowledgments: SBC and SW were supported by the MRC and the McDonnell-Pew Foundation during the period of this work. VS was supported by the Anglia and Oxford NHS. JL was supported by the Isaac Newton Trust. Steve Cooter, Rachel Treadaway, Becky Hannon, and Nic Alexander carried out invaluable pilot studies for this study, as part of their final year undergraduate project, for which we are grateful. We are also indebted to Southlands School, Hampshire, and Wolverhampton Grammar School for their co-operation. Special thanks to Maggi Rigg, Ann Wakeling, and Tony Bennett for opening their schools to us. kinds of entity: those that have intentionality, and those that do not (Brentano, 1874/1970)1. The animate-inanimate distinction doesn’t quite cover the intentional/non-intentional distinction in that plants are of course alive, so the distinction is better covered by the concept of agency (Premack, 1990). Agents have intentionality, whereas non-agents do not. This also means that when agents and non-agents move, their motion has different causes (Csibra, Gergely, Biro, Koos & Brockbanck, 1999; Gelman & Hirschfield, 1994). Agents can move by self-propulsion, which we naturally interpret as driven by their goals and desires, whilst nonagents can reliably be expected not to move unless acted upon by another object (e.g., following a collision). We assume that the task for hominids as information-processors, over millions of years, has been to compute the causes of these two distinct classes of motion rapidly, since to fail to do so would be self-evidently maladaptive. Dennett’s claim is that humans from infancy onwards use folk (or intuitive) psychology to deduce the cause of an agent’s actions, and use folk (or intuitive) physics 2 to deduce the cause of a non-agent’s movement (Dennett, 1987). Thus, if we see a rock rolling down the hill, and an agent is present then the event could be interpreted as having been caused by an intention (e.g. to throw it, roll it, kick it, etc.,). If no agent is present, the event could be interpreted in terms of a physical causal force (e.g. it was hit by another object, gravity, etc.,). Sperber, et. al., suggest that humans alone have the reflective capacity to be concerned about causality, and that “causal cognition” broadly falls into at least these two types (Sperber, Premack & Premack, 1995). It may be that aptitudes in folk psychology and folk physics are independent of one another, or are inversely related to one another. The experiments reported below are relevant to these possibilities, since they investigate if some individuals are impaired in their folk psychology but not in their folk physics, and if others show the opposite pattern. Folk psychology and folk physics may also be under some degree of genetic control. That is, they may comprise modules in a minimally innate sense (Baron-Cohen, 1999). One way one can test if such mechanisms are under some degree of genetic control is by testing for dissociations in individuals who are known to have a genetic disability. In the studies to be reported, we take this approach by investigating folk psychology and folk physics in children with Asperger Syndrome (AS). Before turning to AS, it is necessary to define folk psychology and folk physics, and to consider the evidence from normal development which points to these being “core domains of cognition” (Wellman & Inagaki, 1997). 48 BARON-COHEN ET AL. 1 Intentionality is defined as the capacity of something to refer or point to things other than itself. A rock cannot point to anything. It just is. In contrast, a mouse can “look” at a piece of cheese, and can “want” the piece of cheese. 2 We use the terms “folk psychology” “intuitive psychology”, and “theory of mind” interchangeably. We also intend the terms “folk physics” and “intuitive physics” to be interchangeable. Defining Folk Psychology and Folk Physics We define folk psychology as comprising both low-level social perception, and higher-level social intelligence. Low-level here broadly refers to skills present in human infancy ( Johnson, 2000). These include being able to judge (a) if something is an agent or not (Premack, 1990); (b) if another agent is looking at you or not (Baron-Cohen, 1994); (c) if an agent is expressing a basic emotion (Ekman, 1992), and if so, what type. It also includes (d) engaging in shared attention, for example by following gaze or pointing gestures (Mundy & Crowson, 1997; Scaife & Bruner, 1975; Tomasello, 1988); (e) showing concern or basic empathy at another’s distress, or responding appropriately to another’s basic emotional state (Yirmiya, Sigman, Kasari & Mundy, 1992); (f) being able to judge an agent’s goal or basic intention (Premack, 1990). Higher-level here refers to skills present from early childhood and which continue to develop throughout the lifespan. These include the following: (i) Attribution of the range of mental states to oneself and others, including pretence, deception, belief (Leslie, 1987). (ii) Being able to recognize and respond appropriately to complex emotions, not just basic ones (Harris, Johnson, Hutton, Andrews & Cooke, 1989). (iii) Being able to link such mind-reading to action, including language, and therefore to understand and produce pragmatically appropriate language (Tager-Flusberg, 1993). (iv) Using mind-reading not only to make sense of others’ behaviour, but also to predict it, and even manipulate it (Whiten, 1991). (v) Our sense of what is appropriate in different social contexts, based on what others will think of our own behaviour. (v) Empathic understanding of another mind. In short, it includes the skills that are involved in normal reciprocal social relationships (including intimate ones) and in communication. We recognise that we have defined folk psychology broadly, such that it is unlikely to hinge on a single cognitive process. However, we argue that the domain is quite focused and narrowly defined, namely, understanding social causality. We define folk physics as comprising both low-level perception of physical causality, and higher-level understanding of physical-causality. Low-level here refers broadly to skills present in human infancy, such as the perception of physical causality (Leslie & Keeble, 1987) and expectations concerning the motion and properties of physical objects. Higher-level here refers to skills present from early childhood and which continue to develop throughout the lifespan. These include concepts relating to mechanics (Karmiloff-Smith, 1992). Like folk psychology, folk physics is unlikely to hinge on a single cognitive process. However, like folk psychology, we argue that the domain is quite focused and narrowly defined, namely, understanding how things work. Both folk physics and folk psychology have been proposed as “core domains of human cognition” because they share seven features (Carey, 1985; Gelman & Hirschfield, 1994; Sperber et al., 1995; Wellman & Inagaki, 1997). Both domains (1) are aspects of our causal cognition, (2) demonstrate precocity in human infancy, (3) are acquired or develop universally, (4) show little if any cultural variability, (5) have a specific but universal ontogenesis, (6) are adaptive, and (7) may be open to STUDIES OF THEORY OF MIND 49