UC San Diego

When children are born deaf, many acquire a sign language as a first language (L1) later in life with sparse prior language knowledge because they cannot fully access any spoken languages used around them. This unique circumstance of late L1 acquisition has well-documented and lifelong effects on morpho-syntactic proficiency and neurolinguistic processing. How late L1 acquisition affects phonology, however, is less clear. It is possible that all sign phonological forms (handshapes, locations, and movements) are uniformly affected by late L1 acquisition. An alternate possibility is that late L1 acquisition differentially impacts phonological form processing. These hypotheses were investigated in a series of phonological production and perception experiments that tested deaf early L1, deaf late L1, and hearing late L2 signers, as well as hearing nonsigners for perception tasks. Participants performed lexical decisions and repetitions, similarity judgements, and phonological form monitoring of American Sign Language (ASL) signs and pseudosigns. Crucially, phonological movement was analyzed in all experiments to fill the gap left by its exclusion in previous research. The studies uncovered several novel findings. First, learning ASL after early childhood as an L1 or L2 affects the production of phonological movement, suggestive of a general late signer accent. Second, phonological movement perception is sensitive to the age of L1, and not L2, acquisition. Deaf individuals who acquired ASL as a late L1 had lower movement identification performance in contrast to individuals (deaf or hearing) whose language experience (sign or speech) began in early childhood, regardless of sign language exposure (signer or nonsigner). Together, these results demonstrate that phonological movement processing is exceptionally impacted by late L1 acquisition. Importantly, since movement is integral not only at the phonological level but also at the morphological and syntactic levels in sign languages, impacts on phonological movement processing could underlie effects seen on morpho-syntactic processing.