Lateralized lexical decisions and the effects of hemifield masks: a study of interhemispheric inhibition and release

A lateralized tachistoscope experiment using 40 normal, right-handed men tested the predictions of three different theories of interhemispheric interactions. Lexical decision for function words was measured for each visual field under several conditions of simultaneous stimulation in the contralateral hemifield. When a nonsense word was presented simultaneously to the contralateral hemifield, performance decreased, especially for words in the weaker field, an effect which is inconsistent with the predictions of the direct access model. When the contralateral nonsense word was immediately masked, there was a significant improvement in performance over the nonmasked condition. Analysis of the masking effect showed that the data are inconsistent with a callosal relay model, but are consistent with a model of transcallosal inhibition.