Inducing emotion by unilateral contraction of facial muscles: a new look at hemispheric specialization and the experience of emotion.

Subjects who maintained voluntary contractions of the left facial muscles experienced sadness. Right facial contractions resulted in a more positive but difficult to characterize experience. These contractions had similar effects on the affective tone of stories told about an ambiguous picture. These findings indicate that emotions can be aroused by unilateral muscle contractions without intervening cognitions. They provide a new methodology for studying the roles of the cerebral hemispheres in emotional experience. Finally, they support the conclusion that the right hemisphere is involved with negative emotional experiences and indicate that the left hemisphere is involved with experiences that are more positive but not readily characterized.