ABSTRACT
We do not interpret each other’s speech and actions in terms of surface meaning and behaviour, but in terms of intentions, knowledge and beliefs. This is called “having a theory of mind” and is essential for successful social interactions. Theory of mind has been studied intensively and experimentally in the developing child and has been shown to be grossly impaired in autism. Many of the signs and symptoms of schizophrenia can be understood as arising from impairments in processes underlying “theory of mind” such as the ability to represent beliefs and intentions. Patients with delusions of reference and persecution can represent that other people have different beliefs and intentions from themselves, but have difficulty inferring the content of these beliefs and intentions. This difficulty is the basis of their erroneous beliefs about the intentions of others. Patients with auditory hallucinations and delusions of control cannot distinguish between representations of beliefs and intentions (their own and others) and representations of directly perceived events. As a consequence representations of their own intentions are experienced as alien forces controlling their actions. Representations of the beliefs of others are experienced as auditory hallucinations. Patients with lack of volition and social withdrawal can no longer represent their own wishes and beliefs, or those of others. Being unable to represent their own goals, they have difficulty with spontaneous willed acts and instead show perseverative and stimulus driven behaviour. Lesion studies suggest that successful social interactions require intact frontal and temporal lobes. I propose that representation of a belief requires an interaction between posterior structures and frontal cortex. Posterior structures hold representations of perceptions (such as “it is raining”). Interactions between frontal cortex and appropriate posterior structures permit (a) awareness of perceptions (I know, “it is raining”) and (b) marking of representations as beliefs (John believes, “it is raining”). Schizophrenic symptoms are a consequence of abnormalities in these interactions.
