Distinct Neural Responses to Number Signs and Number Gestures in Hearing Second Language Signers

Understanding the distinction between signs in sign language and gestures has been a topic of interest among researchers over the past decade. Recent arguments emphasize that sign languages exhibit syntactic, semantic, morphological and phonological features, whereas gestures are considered external to language. This theoretical distinction is importantly reflected at the brain level, with distinct brain regions being involved in sign language comprehension and gesture processing. Using a fast periodic visual stimulation (FPVS) EEG design, the present study investigated whether this distinction is modulated by sign language knowledge in hearing adults. We compared neural responses of late hearing signers and hearing non-signers to finger-number configurations presented either as number signs (finger-montring) or number gestures (finger-counting). Results revealed that hearing signers showed significantly stronger neural discrimination responses to number signs than hearing non-signers, whereas both groups exhibited similar responses to number gestures. These findings demonstrate that number signs and number gestures elicit distinct neural responses as a function of linguistic experience. Crucially, they show that even late acquisition of sign language is sufficient to modulate neural processing of manual number representations, supporting the view that sign language recruits language-specific neural mechanisms. More broadly, these results provide neurophysiological evidence that manual configurations can be processed either as linguistic signs or as gestures depending on the observer's language knowledge, thereby underscoring the linguistic status of sign languages.