Three Conundrums of Language Lateralization

The lateralization of language to the left hemisphere of the brain in most right-handed individuals is well established; however, this arrangement has no widely accepted theoretical explanation. The distribution of language across the cerebral hemispheres raises issues and contradictions that are difficult for any theory to accommodate. In this article, we review three puzzles about the lateralization of language: (1) the clinical literature reveals profound deficits in language only after left-hemisphere damage, but the brain imaging literature shows bilateral activation in most language tasks; (2) language is left-hemisphere dominant in most individuals yet deviation from this pattern does not result in language dysfunction; and (3) lateralization and handedness are related, but the factors that underlie this relation are unknown. We also briefly discuss evolutionary and genetic theories that have been advanced to explain lateralization.