Theory of mind or mentalization refers to the ability to make inferences about the mental states of others: their intentions, desires and beliefs. Numerous studies use brain imaging to explore the neural basis of these abilities, and their results are highly consistent. Activity is observed in the medial prefrontal cortex (mPFC), in the superior temporal sulcus at the junction with the parietal lobe (STS/JTP), as well as in the temporal poles and posterior cingulate cortex. To understand this brain system, we must first understand the mechanisms involved in mentalization.
An important clue to the intentions of others comes from the movements they make. This can be explained as follows: by simulating these movements on our own through the brain's mirror system, we can directly infer the intention behind them. But this bottom-up mechanism doesn't explain why the same movement can reflect different intentions. We can solve this problem by using a predictive coding mechanism identical to the one used to resolve ambiguities in sensory perception. It's a top-down mechanism that begins with a prior hypothesis about the agent's likely intention, given the context. The brain's mirror system then predicts the most likely movement based on this prior hypothesis. Any discrepancy between the predicted movement and that actually observed indicates a prediction error, and enables the hypothesis concerning the agent's intentions to be revised. A large number of studies suggest that activity in STS/JTP reflects the extent of this prediction error. This appears to be the case even when intentions are inferred from cues other than movements.
