Mind over grammar: reasoning in aphasia and development.

Research on propositional reasoning (involving 'theory of mind' understanding) in adult patients with aphasia reveals that reasoning can proceed in the absence of explicit grammatical knowledge. Conversely, evidence from studies with deaf children shows that the presence of such knowledge is not sufficient to account for reasoning. These findings are in keeping with recent research on the development of naming, categorization and imitation, indicating that children's reasoning about objects and actions is guided by inferences about others' communicative intentions. We discuss the extent to which reasoning is supported by, and tied to, language in the form of conversational awareness and experience rather than grammar.