Right hemisphere advantage for evaluating emotional facial expressions.

The ability to evaluate the intensity of emotional facial expressions was investigated in patients undergoing the intracarotid sodium amytal procedure. It was found that when the hemisphere non-dominant for language (usually right) was anesthetized, the patients' ratings of the intensity of emotional expressions in photographs were lower than baseline ratings of these expressions. Such an effect was not seen with anesthetization of the hemisphere dominant for language (usually left). Ratings of shades of gray (which served as control stimuli) showed no such effect. The findings are interpreted in terms of a right hemisphere superiority in the perception and evaluation of emotional expression.