Introduction

One topic that is strikingly pervasive across the cognitive sciences is that of Theory of Mind, referring to the abilities that people have in reasoning about their own mental states and those of others. It is the set of Theory of Mind abilities that enable people to reflect introspectively on their own reasoning, to empathize with other people by imagining what it would be like to be in their position, and to generate reasonable expectations and inferences about mental states and processes.

Although there are inherent difficulties involved in investigating behavior that is largely unobservable, a relatively sophisticated understanding of Theory of Mind abilities has emerged through the synthesis of widely disparate sources of evidence. This evidence suggests that Theory of Mind abilities progressively develop in children and adults (Happé et al., 1998; Wellman and Lagattuata, 2000), are degraded in people diagnosed with the illness of autism (Baron-Cohen, 2000), have a relationship to localized brain regions (Happé et al., 1999; Frith and Frith, 2000), and are a uniquely human cognitive faculty not available to other primates, e.g. chimpanzees and orangutans (Call and Tomasello, 1999). This last contribution to our understanding of Theory of Mind suggests that these abilities must have arisen in the human lineage only after a split from that of chimpanzees some 6–8 million years ago (but see Stanford, this volume, for a review of dissenting opinions).