Hemiregional variations in facial expression of emotions

This study examined expressiveness of facial regions during posed expressions of two basic emotions: happy and sad. Two types of composite photographs were prepared: hemifacial composites of left-left (LL) or right-right (RR); and hemiregional composites involving a left-left composite in the upper part and a right-right composite in the lower part (LL/RR) of the face or vice versa (RR/LL). Participants ranked photographs of an emotion expression: normal orientation (RL), mirror reversed (LR), left facial composite (LL), right facial composite (RR) and hemiregional composites (RR/LL; LL/RR), in order of expressiveness. The hemiregional composite RR/LL was judged as most expressive followed by LL. The findings are explained in terms of the neuroanatomy of fibre projections from the left and right cerebral hemispheres to the facial muscles.