Induced smiling stabilizes visual awareness of positive images during binocular rivalry

How do observers’ facial expressions influence their conscious perception of emotionalstimuli? Previous work using binocular rivalry has shown that manipulating participants’ facialmovements shapes visual awareness of rivalrous facial expressions, but the underlyingmechanism remains unclear. Does facial muscle configuration selectively enhance perceptionof matching expressions, suggesting sensorimotor simulation, or does it more broadly affectemotional stimuli in general, consistent with the facial feedback hypothesis? To investigatethis, forty female participants from a Western university population held a chopstickhorizontally between their teeth (activating smile-associated muscles) or had their facialmovements unrestricted during binocular rivalry between competing images. We tested tworivalry conditions: one included face stimuli and the other included two non-facial objects,ensuring that facial and non-facial stimulus pairs were matched for arousal and valence ratings.Participants rated the smiling face (M=2.3) and flower (M=1.8) as more positive than theneutral face (M=0.2) and storage item (M=-0.3) on a -3 to +3 scale. We measured the durationof each stimulus’s dominance in visual awareness during 60-second rivalry periods. Notably,the chopstick manipulation increased dominance duration for both facial and non-facial stimulirated as positive—the smiling face (+2.5s, d=0.38) and flower (+2.1s, d=0.35)—whileneutrally-rated stimuli showed no change. These results provide initial evidence that facialmuscle configuration can bias visual awareness for positive content across stimulus classes,supporting the role of facial feedback. Although based on limited stimuli that requirereplication, the findings suggest that embodied states may influence conscious perception morebroadly than previously recognized.