Supplementary material from "Theory of Mind and the brain substrates of direct and indirect communicative action understanding"

Grasping the speaker’s communicative intention based on the verbal utterance and its context is one of the key aspects of human interaction. This ability relies on Theory of Mind (ToM), that is, the cognitive processing of mental states, beliefs, and desires of others. We review evidence that, during indirect speech act understanding, those areas typically engaged in ToM processing, particularly the medial prefrontal cortex and bilateral temporoparietal junction, become active. However, other studies show a degree of variability of these ‘ToM area activations’ during indirect communication and demonstrate that the same areas are activated for specific communicative functions – such as requests, promises or questions – per se, even if they are expressed directly. Furthermore, we show that studies on indirectness of communication raise questions about the role of different communicative function types in drawing upon ‘ToM regions’. We attempt to relate cortical area activations to the commitments, assumptions, and intentions that the interlocutors make when processing specific communicative function types. In essence, all communicative actions, including both direct and indirect ones, have in common that relevant knowledge about others’ intentions and beliefs needs to be processed by the interlocutors.