Hemispheric asymmetry in long-term semantic relationships

Abstract

Latencies in a category membership decision task were used to investigate hemispheric organisation of concepts in long-term semantic memory (LTSM). The experiment used the hemi-field technique to lateralise pictures representing high versus low typicality instances of pre-designated concepts to the right and left hemispheres. The results demonstrated hemispheric asymmetries in storage/retrieval of category members. In the right hemisphere, latencies were shorter for high than for low typicality members, consistent with previously reported prototypicality effects in free vision (Rosch, 1975), whereas for the left hemisphere, no dissociation was found. The results are interpreted in terms of two distinct conceptual organisations in the brain, one specialised in the right hemisphere and based on family resemblances/prototypicality, and one specialised in the left hemisphere and possibly based on necessary and sufficient/logical definitions. The view adopted is that typicality effects are not obligatory in all classification systems.