Extrafoveal processing of happy face relies on visual awareness in hearing-impaired adults

Hearing loss is the most common sensory deficit. Deaf adults outperform hearing adults in terms of the visual processing of extrafoveal moving stimuli and fearful facial expressions, probably due to compensatory mechanisms. However, it remains unresolved whether these enhanced visual abilities also apply to happy facial expressions, which are the most universally recognized and prioritized prosocial signals among all the facial expressions. To address this question, we aimed to investigate hearing-impaired adults' processing of happy faces at unconscious (Experiment 1) and conscious (Experiment 2) levels. In Experiment 1, we paired backward-masked faces with supraliminal faces in both visual fields and asked participants to perform a go/no-go task only for the supraliminal faces. Results revealed that the discrimination of visible emotional faces (either happy or neutral) was modulated by the facial expressions of the backward-masked faces in the opposite visual field. The emotionally congruent condition showed higher accuracy than the incongruent condition. However, this effect was observed only for participants whose visual awareness of backward-masked faces was above the chance level in the final awareness check task. Results of Experiment 2 demonstrated that the conscious processing of happy faces remained intact in hearing-impaired adults, as reflected in the happy-face recognition advantage in reaction time. Overall, these findings imply that extrafoveal happy face processing relies on visual awareness in hearing-impaired adults. The present study provides insights into the visual perception ability of facial expressions in the hearing-impaired population.