Interhemispheric integration in visual search

► All subjects showed a significant bilateral field advantage in a visual search task. ► The group mean scanning speed is 20% faster for bilateral vs. unilateral displays. ► Bilateral field advantage (BFA) is absent for the target-absent condition, implying. ► BFA reflects intrahemispheric competition in a 1st, parallel stage of guided search. ► Interhemispheric competition in the 2nd, serial stage of guided search.