Interhemispheric cooperation and activation in integration of verbal information

Subjects had to judge the semantic relation between two tachistoscopically presented German adjectives. In Exp. I, the two words were projected simultaneously, either both to the left visual field (i.e. to the right hemisphere, LVF-RH), or both to the right visual field (i.e. to the left hemisphere, RVF-LH), or one word to each visual field (i.e. to both hemispheres, EVF-BH). The results yielded a significantly higher performance in the condition EVF-BH than in the two unilateral conditions, without a significant difference between the latter two conditions. In Exp. II, the two words were shown successively. With bilateral presentation, a distinction was made as to whether the left visual field (EVF-BH-L) or the right visual field (EVF-BH-R) was stimulated first. The significantly highest performance was shown in conditions RVF-LH and EVF-BH-R compared with the condition EVF-BH-L, and the significantly poorest performance in the condition LVF-RH compared with the condition EVF-BH-L. The results provide evidence for (1) an intrahemispheric interference with simultaneous unilateral presentation, (2) a cooperative interhemispheric interaction with simultaneous bilateral presentation, and (3) an interhemispheric priming effect with successive bilateral presentation when the left hemisphere was stimulated first.