The human conceptual system contains knowledge that supports all cognitive activities,
including perception, memory, language and thought. According to most current theories,
states in modality-specific systems for perception, action and emotion do not represent
knowledge - rather, redescriptions of these states in amodal representational languages
do. Increasingly, however, researchers report that re-enactments of states in modality-specific
systems underlie conceptual processing. In behavioral experiments, perceptual and
motor variables consistently produce effects in conceptual tasks. In brain imaging
experiments, conceptual processing consistently activates modality-specific brain
areas. Theoretical research shows how modality-specific re-enactments could produce
basic conceptual functions, such as the type-token distinction, categorical inference,
productivity, propositions and abstract concepts. Together these empirical results
and theoretical analyses implicate modality-specific systems in the representation
and use of conceptual knowledge.