Asymmetrical hemispheric activation and behavioral persistence: effects of unilateral muscle contractions.

Contractions of the left hand and of the left side of the lower third of the face induce negative emotional states whereas right-sided contractions induce positive states. Contractions also have mood-congruent influences on perception. This article reports that contractions affect behavior as well. Persistence in attempting to solve insoluble problems is greater following right-sided contractions than following left-sided contractions. This effect is unrelated to dominance of the contracted muscles because right-handed individuals tend to be left-face dominant. Results support the hypothesis that unilateral contractions activate the contralateral cerebral hemispheres and arouse the hemispheres' respective functions with regard to emotion and behavior.