Interhemispheric communication of abstract and specific visual-form information

Pairs of letters were compared after being viewed in different visual fields (i.e. across-hemi spheres, AH) or in the same visual field (i.e. within-hemi sphere, WH). In an abstract-category comparison task, participants decided whether two letter exemplars belonged to the same abstract category (e.g. k and K) or not (e.g. k and P) and performed more accurately in AH trials than in WH trials. In a specific-exemplar comparison task, they decided whether two letters within the same abstract category were the same specific exemplars (e.g. k and V) or not (e.g. k and K) and performed more accurately in WH trials than in AH trials. This pattern of results was observed when the exemplars in a category were visually similar (e.g. k and K, a and a) but not when they were visually dissimilar (e.g. a and A). The reversed association technique was used to confirm the independence of subsystems underlying abstract category and specific-exemplar comparisons. Most important, the results support the theory that a specific-exemplar subsystem is more detrimentally affected by interhemispheric transfer of information than an abstract category subsystem. (C) 2002 Elsevier Science Ltd. All rights reserved.