Differences in biological motion perception associated with hearing status and age of signed language exposure

Abstract

This study investigates how American Sign Language (ASL) fluency and hearing status influence the perception of biological motion, using three point-light display (PLD) tasks. Prior research indicates that early exposure to ASL among deaf signers results in more rapid and effortless recognition of biological motion than hearing non-signers, potentially due to the expertise in deciphering complex human movements, or possibly due to neuroplasticity in deaf brains. However, it remains uncertain whether this advantage stems from signed language proficiency or the experience of being deaf. To explore this, we designed three PLD tasks involving the assessment of the direction of randomly moving dots, identifying a person from biological motion PLDs, and determining whether right-side-up and inverted PLDs depict actions involving a ball. A diverse cohort of participants (N = 229) with varying ASL fluencies and hearing statuses completed the tasks online, providing us with reaction time and accuracy data. Overall, participants who know ASL (regardless of hearing status) showed faster (ps < .001) and more accurate (ps < .001) responses across all three tasks. Our results suggest that earlier ASL exposure leads to higher accuracy on complex action identification tasks (p = .002). Furthermore, reaction time analysis demonstrated a speed-accuracy tradeoff in deaf participants, indicating a potential advantage in motion perception speed (p < .005) at the cost of accuracy (p < .001). We conclude that ASL fluency and hearing status both significantly contribute to variations in biological motion perception, with implications for understanding visual expertise and cognitive processing in both deaf and signing populations.