Effects of bilateral stimulation and stimulus redundancy on interhemispheric interaction.

Recent visual laterality studies have included trials in which critical stimulus information is presented simultaneously in both visual half-fields and, thereby, simultaneously to both cerebral hemispheres. To investigate interhemispheric interaction, researchers compare performance on bilateral redundant trials with performance on unilateral trials in which a single copy of the target is presented to one hemisphere or the other. The authors used the identification of nonword letter trigrams to examine the relationship between unilateral and bilateral performance when the 2 types of trials were equated for the number of locations stimulated (Experiment 1) and the number of redundant copies of the target (Experiment 2). Results suggest that when the number of stimulated locations is held constant, each of 2 copies of a target stimulus can be processed with the same efficiency and the same strategy as it would have been had it been the only copy.