Blocking facial mimicry during binocular rivalry modulates visual awareness of faces with a neutral expression

Abstract

Sensorimotor simulation models propose that sensorimotor brain regions play an important role in recognizing and understanding others’ emotions. In particular, the sensorimotor re-enactment by the observer would assist the recognition and understanding of emotions. In this vein, several studies have manipulated the observer’s facial mimicry during a variety of facial expression recognition tasks providing evidence in favor of the role of facial mimicry in emotion recognition. In this theoretical context, a particularly intriguing facet has been neglected, namely whether sensorimotor simulation and facial mimicry can play a role in the conscious processing of facial expressions of emotions. In the present experiment we implemented a binocular rivalry paradigm to investigate whether facial mimicry is functionally associated with conscious processing of facial expressions and in particular in accessing awareness and/or stabilizing conscious representations of emotional expressions. On each trial, female participants were exposed to a rivalrous pair of a neutral and a happy expression of the same individual through anaglyph glasses in two conditions: in one, they could freely use their facial mimicry, in the other they had to keep a chopstick between their lips. The latter manipulation constrained the mobility of the zygomatic muscle, producing a ‘noise’ at the level of the sensorimotor simulation. Our results confirmed previous evidence of an advantage of emotional faces when compared to neutral faces. Crucially, they also confirmed the main hypothesis that facial mimicry has a role on the conscious processing of facial expressions. More specifically, this role appears to be associated with the stabilization of conscious representations of expressions rather than facilitation of conscious access, as mimicry manipulation impacted an estimate of time of facial expressions dominance rather than affecting the frequency of the initial percepts and their onset time (i.e., first button press time). Taken together, our results open a door to the future investigation of the intersection between sensorimotor simulation models and conscious perception of emotional stimuli.