Where in the Brain Is Nonliteral Language?

Abstract

This review examines brain processing of nonliteral expressions that are familiar in form and meaning to the native speaker, such as idioms, proverbs, swearing, and speech formulas. The properties of stereotyped form and conventional meaning distinguish nonliteral utterances from novel expressions. An historical overview of preserved "automatic" speech in aphasia and impaired nonpropositional speech in other neurological diseases suggests that these kinds of language are stored and processed in the brain differently from newly created language. For production, lesion studies and other neurobehavioral observations associate nonliteral expressions with right hemisphere and subcortical structures. Comprehension studies implicate the right hemisphere. Although the entire brain is required for optimal performance, a right hemisphere—subcortical circuit may be important for processing of nonliteral expressions. A dual process model comprised of a holistic mode for nonliteral expressions and a compositional mode for novel language, drawing on disparate neurological structures but continuously in interplay, is proposed.