Qualitative hemispheric differences in semantic category matching

A unilateral category matching task with words as stimuli was employed to i nvestigate semantic processing in the right and left hemispheres (RH, LH). An overall right visual field (RVF)/LH dominance was observed and performan ces were better than chance, also in the left visual field (LVF)/RH. A qual itative analysis of reaction times with individual differences multidimensi onal scaling (INDSCAL) revealed that LVF/RH INDSCAL solutions were signific antly more differentiated in structure than RVF/LH solutions in terms of nu mber and size of dimensions. These findings support a depth of activation h ypothesis of hemispheric processing, with the LH rapidly and focally and th e RH slowly and diffusely activating the semantic network. (C) 1999 Academi c Press.