Effect of unilateral contraction of hand muscles on perceiver biases in the perception of chimeric and neutral faces.

ABSTRACT

Judgements of chimeric faces (half sad, half happy) showed a strong negative bias when the left face was negative. Contractions of the right hand reduced this bias but left hand contractions had no effect. The left positive faces elicited weak positive response biases that were not strongly affected by either contraction. Faces that were drawn to be neutral elicited negative or positive response biases depending on the method of presentation. When this bias was negative under control conditions left contraction had no effect, but the bias became positive following right contractions. Similarly, when the control bias was positive the right contraction had no effect, but the bias became negative following left contractions. The results are interpreted as reflecting emotional changes and shifts in lateral attention resulting from activation of the hemisphere contralateral to the contraction.