Abstract
Reaction times are shorter when congruent emotional expressions are presented to both visual hemifields contemporarily than when just one expression is presented unilaterally to either the left or right hemifield. Here we tested whether the shorter latency in the bilateral congruent condition is present also when the two pictures show the same emotion but belong to two different classes of stimuli. Fearful and happy facial and bodily expressions were presented for 200 ms according to the following six conditions for each of the two emotions: unilateral left, unilateral right, bilateral congruent I (with both stimuli belonging to the same category and showing the same emotion; either both faces or both bodies), bilateral congruent II (with a face on one hemifield and a body on the opposite hemifield, both showing the same emotion), bilateral incongruent I (one happy and one fearful expression with both stimuli of the same class) and bilateral incongruent II (one happy face and one fearful body or vice-versa). We used a go/no-go task and the subjects were required to press a key when the target emotion (fearful or happy, depending on blocks) was presented on the screen (irrespectively of its position, number, or category). Subjects reacted faster to bilateral congruent I and II conditions as compared to unilateral left or right conditions. This difference in reaction times is consistent with an interpretation in terms of interhemispheric cooperation. The present results suggest that physical similarities between stimuli are not relevant for interhemispheric cooperation to occur.