Differences in asymmetric perception of facial expression in free-vision chimeric stimuli and reaction time.

Two forms of a Chimeric Faces Free-Vision Task used to estimate cerebral asymmetry for perceiving facial expression were given to young male subjects, n = 60 in a first session and n = 40 in a retest session. Test-retest and split-half reliabilities were high. As expected from assumptions of right-hemisphere specialization for processing expression, faces with left-sided smiles were more frequently judged as looking happier than those with right-sided smiles in both forms. However, there were individual differences in direction and extent of bias, which were systematically related to reaction time, right visual field-biased subjects being slower. Differences in lateral bias as well as in reaction time are assumed to reflect individual patterns of hemispheric activation, whereas the average left bias in the present male group may reflect right-hemisphere specialization for processing of facial expression.