Effect of response programming on hemispheric differences in lexical decision.

A lateralized tachistoscopic lexical decision task with concrete nouns and orthographically regular nonwords was administered to normal subjects in three conditions using unimanual responses: Yes-No, Go-NoGo with nonword targets, and Go-NoGo with word targets. There was an overall right visual field advantage in accuracy and sensitivity, an interaction between visual hemifield and wordness in latency, and an overall "word" bias. No effect interacted with experimental conditions, showing that response programming did not affect hemispheric asymmetries. The data suggest independent lexical access and similar response programming in each hemisphere. These results are examined in light of three psycholinguistic models of lexical access and are interpreted to support instead a fourth one which posits separate and parallel computations for word decisions and for nonword decisions in each hemisphere.