The  effects of arousal and valence on facial electromyographic asymmetry during  blocked picture viewing

The  effect of stimulus valence and arousal on facial electromyographic (EMG)  asymmetry was investigated to inform the debate about two contrasting hypotheses  of emotion: the right hemisphere dominance hypothesis and the valence  hypothesis. EMG was recorded from the left and right corrugator and zygomaticus  muscles while participants (N=21) viewed blocks of negative and positive  pictures that were high or low in arousal. Ratings of valence and arousal were  taken before and after each of the four emotion blocks. Corrugator muscle  activity yielded evidence for left hemi-face dominance during high and low  arousal negative picture blocks whereas zygomaticus muscle activity yielded  evidence for right hemi-face dominance during high arousal positive picture  blocks, especially early during the picture sequence. This pattern of results is  consistent with the valence  hypothesis.

International  Journal of Psychophysiology 79 (2011)  378–384

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