Categorical Perception of Labeled and Unlabeled ASL Facial Expressions in Hearing Non-signers

Previous research has demonstrated categorical perception (CP) of facial expressions from American Sign Language (ASL) in hearing, English-speaking non-signers. Notably, CP was observed even for faces with no obvious linguistic labels in English, suggesting the existence of covert categories based on nonlinguistic facial properties. However, in the earlier work, CP was assessed using memory procedures, leaving open the possibility that such categories have no impact on the discrimination of simultaneously presented faces. Here, we used a visual search task with no memory component to test for CP for both labeled (happy/sad) and unlabeled (adverbial expressions with no lexical signs) categories of ASL facial expressions. CP was observed for both sets of categories, suggesting that unlabeled covert categories——not just labeled ones——are accessed even when stimuli are readily available to perception. We interpret these findings in light of competing accounts of the interrelations of language, categories, and perception.