How expertise can alter effects of face masks: investigating a sample of congenitally deaf participants?

A face mask covers the lower part of the face and thereby limits social communication. Only unoccluded face regions like the eyes and eye region remain informative in communication, which might be especially helpful for expert face readers such as the deaf population. We assessed the effects of face masks in a sample of 59 congenitally deaf participants. Participants rated faces with and without face masks for the following characteristics: arousal and valence of three facial expressions (happy, neutral, sad), invariant characteristics (sex, age), and trait-like characteristics (attractiveness, trustworthiness, approachability). The experiment was a replication of a previous study conducted on hearing participants. Results indicated that, when compared to no-masked faces, the deaf experienced reduced valence intensity in masked faces across all expressions. However, perceived arousal was only reduced for happy expressions in masked faces. Masked faces also appeared older and borderline more approachable. These results mostly mimicked data from the hearing, despite the deaf having greater expertise reading faces. Therefore, expert face readers also succumbed to the effects of face masks as the perceived intensity of facial expressions becomes reduced. An additional post-hoc analysis comparing the effects of face masks between deaf and hearing samples revealed distinct biases between the two populations. When evaluating facial expressions, the deaf showed stronger biases for full-faces than the hearing. When rating traits, the deaf were more biased by face masks whereas the hearing were more biased by full-faces. Implications for effects of expertise on face processing are discussed.