What's domain-specific about theory of mind?

Twenty years ago, Baron-Cohen and colleagues argued that autistic performance on false belief tests was explained by a deficit in metarepresentation. Subsequent research moved from the view that the mind has a domain-general capacity for metarepresentation to the view that the mind has a domain-specific mechanism for metarepresentation of mental states per se, i.e., the theory of mind mechanism (ToMM). We argue that 20 years of data collection in lesion patients and children with autism supports a more parsimonious view closer to that of the 1985 paper. Lower-level domain-specific mechanisms--e.g., tracking gaze, joint attention--interacting with higher-level domain-general mechanisms for metarepresentation, recursion, and executive function can account for observed patterns of deficits in both autism and neurological patients. The performance of children with autism or orbitofrontal patients on ToM tests can be explained more parsimoniously by their deficits in lower-level domain-specific mechanisms for processing social information. Without proper inputs, the intact capacity for metarepresentation by itself cannot make correct ToM inferences. Children with autism have no impairment in false photograph tests because their metarepresentational capacity is intact and they have no impairment in inputs required for such tests. TPJ patients have equivalent deficits on ToM and non-ToM metarepresentational tasks, consistent with a failure in domain-general processing. If deficits on ToM tasks can result from deficits in low-level input systems or in higher-level domain-general capacities, postulating a separate ToM mechanism may have been an unnecessary theoretical move.