What the face reveals: Contributions of facial electromyography to the detection of emotional and identity changes

To recognize peers and differentiate between them is a crucial ability that enables organisms to engage in survival and appetency behavior. In
many animal species, such as insects and rodents, recognition and differentiation is achieved through olfac'on. Humans, in contrast, rely heavily on visual information, mainly conveyed by our facial expressions. It has been proposed that facial mimicry and imitation are crucial building blocks of human affect understanding. In this view, afferences from the underlying facial mechanoreceptors and the accompanying movements of the face, provide the necessary proprioceptive information that gives rise to subjective feelings However, it remains unclear, how and up to what extent these facial afferences specifically contribute to our awareness of emotional versus non- emotional changes of facial displays . To investigate this issue, we recorded facial electromyography during a paradigm of change detection of facial expressions. In the task, video morphs of gradual changes of faces, evolving from a neutral to a happy, angry face, or a different identity, were presented to track the moment when subjects become aware of a new facial display. Participants were instructed to press a button at the moment they detected a change towards a new display. In addition, the subjects were invited to identify the type of change they had detected (accuracy) and to rate the level of vividness of the detected change (subjective experience).