Hemispheric differences in the perception of positive and negative faces.

Thirty-two right-handed subjects (15 males and 17 females) participated in a study investigating the effects of the perception of positive and negative emotional stimuli on choice reaction time. Slides of faces showing positive (happy, surprise) or negative (anger, disgust, sadness) affect were presented via a tachistoscope to either the right or left visual field. A 2 X 2 X 2 X 2 mixed analysis of variance with repeated measures over the factors of hand used by visual field by affect across sex of subject revealed a main effect for visual field (with slightly faster responses to stimuli presented in the right visual field) and a strong affect by visual field interaction with positive facial slides identified more quickly than negative facial slides when presented to the right visual field.

Superiority of the left hemisphere in the recognition of emotional faces.

Thirty-two right-handed university students (16 males and 16 females) participated in a choice reaction time study assessing the perception of hemispheric differences in positive (happiness, surprise) and negative (anger, disgust) facial affect. Subjects were exposed to slides of facial expressions in either the left or right visual field, and latency of affect identification was measured by having each subject move a lever forward or backward in a specified direction to indicate the emotion perceived. An analysis of variance with repeated measures over hand used, visual field, and affect across sex of subject revealed significant main effects for visual field, affect and sex of subject. In contrast to prior studies, the emotional faces were perceived faster in the right visual field than in the left visual field. This finding is explained in terms of the more demanding analytical task chosen in contrast to previous research which typically employed a holistic matching or recognition task. The faster perception of positive affect may be attributed to the increased salience of the facial cues present in those faces displaying happiness or surprise. Finally, the faster response of males supports existing data suggesting greater cerebral lateralization in the male brain.