Concreteness: nouns, verbs, and hemispheres.

The preferential processing of concrete versus abstract nouns, and of active versus static or "quiet" verbs, was investigated using a lateralized lexical decision task in 32 normal and 4 commissurotomized subjects. Both groups of subjects showed the concreteness effect for nouns in both visual fields. The disconnected right hemisphere of two commissurotomized subjects responded with above chance performance only to concrete nouns. Neither group showed an activeness effect for verbs in either visual field. This supports an imageability rather than a multisensory representation interpretation of the concreteness effect. A comparison of responses to words and to nonwords revealed that males had a "no" bias to stimuli in the left visual field, and both males and females showed a slight "yes" bias for stimuli in the right visual field. These data suggest that the lexical decision task is complex and that word and nonword decisions constitute partly independent functional components. We interpret the sex differences as an indication of strategic rather than functional differences in lateralization patterns between males and females.