Phonological similarity judgments in ASL: Evidence for maturational constraints on phonetic perception in sign

We created a novel paradigm to investigate phonological processing in sign and asked how age of acquisition (AoA) may affect it. Participants indicated which of two signs was more phonologically similar to a target, and estimated the strength of the resemblance with a mouse click along a continuous scale. We manipulated AoA by testing deaf native and non-native signers, and hearing L2 signers and sign-naïve participants. Consistent with previous research, judgments by the native and L2 signers reflected similarity based on shared phonological features between signs. By contrast, judgments by the non-native signers and sign-naïve participants were influenced by other (potentially visual or somatosensory) properties of signs that native and L2 signers ignored. These results suggest that early exposure to language helps a learner discern which aspects of a linguistic signal are most likely to matter for language learning, even if that language belongs to a different modality.