Sex differences found in facial EMG activity provoked by viewing pleasant and unpleasant photographs.

50 male and 50 female participants' facial electromyographic (EMG) activity at the left corrugator and zygomatic muscle regions and self-reports of emotions were recorded while they were viewing Pleasant and Unpleasant photographs. Analysis showed that the ratio of EMG power between the periods of photograph viewing and baseline at the zygomatic muscle region was significantly higher than that at the corrugator muscle region while viewing Pleasant photographs and that the EMG ratio at the corrugator muscle region was significantly higher than that at the zygomatic muscle region while viewing Unpleasant photographs. Further analysis indicated that compared to men, women reported relatively higher feelings of pleasantness and generated significantly higher EMG ratios at the zygomatic muscle region while viewing Pleasant photographs and women reported significantly less feelings of pleasantness and generated significantly higher EMG ratios at the corrugator muscle region while viewing Unpleasant photographs. These results demonstrate the sex effects on emotion expression and associated EMG responses while viewing emotion provoking photographs.