Unilateral right-hand contractions cause contralateral alpha power suppression and approach motivational affective experience.

Contractions of the left hand induce sadness and bias judgments negatively, whereas contractions of the right hand induce positive affect and assertiveness and bias judgments positively. These results have been explained as resulting from activation of right and left frontal cortices, respectively. However, no research has tested this explanation. The present experiment provided such a test by having participants contract the right or left hand while electroencephalographic activity was recorded. Results indicated that right-hand contractions produced greater left than right frontal activity, whereas left-hand contractions produced greater right than left frontal activity (inverse of alpha power). Similar activations occurred in central regions, perhaps due to mu rhythms. Moreover, as compared to left-hand contractions, right-hand contractions caused greater self-reported approach affect to a mildly positive radio editorial.