Hemispheric Asymmetry in Expression and Perception of Happiness

Abstract

Hemispheric asymmetries in happiness expression -which has an important role in interpersonal communication and its perception- have been studied using different techniques. However, it is not clear whether the source of the asymmetry is the poser or the observer. In Experiment I, we investigated on which hemiface (right/left) the expression of happiness was better identified. Subjects evaluated right-sided happy chimeric faces as more expressive. In Experiment II, we examined whether the source of the bias was the observer's hemispheric asymmetry or the poser's facial asymmetry. Stimuli were briefly presented unilaterally, either in the left visual field(LVF)/right hemisphere(RL) or in the right visual field(RVF)/left hemisphere(LH). Faces were recognized faster in LVF condition, but they were evaluated as more expressive in RVF condition. Right-sided happy faces were found to be more expressive in RVF condition. Results indicated LH superiority in the recognition of happy expression and a RH superiority in the duration of facial processing. Additionally findings pointed out a sex difference in subjects' evaluation time and evaluation scores. Men evaluated the stimuli faster in the RH condition than they did in the LH condition; while women evaluated the faces with higher scores in LH than they did in RH condition.