First-language acquisition after childhood differs from second-language acquisition: the case of American Sign...

Area of Science:

• Linguistics
• Developmental Psychology
• Neuroscience

Background:

• The long-term outcomes of first-language acquisition initiated after early childhood are not well understood.
• Comparing first and second language acquisition in deaf adults provides insight into critical periods for language development.

Purpose of the Study:

• To determine if first-language acquisition of American Sign Language (ASL) after early childhood results in similar long-range outcomes as second-language acquisition.
• To investigate the impact of age of acquisition on ASL sentence processing and memory.

Main Methods:

• Study included 36 deaf adults with varied ASL and spoken English acquisition histories.
• ASL sentence processing was assessed via recall of complex sentences and short-term memory for signed digits.
• Participants were categorized based on whether ASL was acquired as a first or second language and the age of acquisition.

Main Results:

• Adults acquiring ASL as a second language after childhood outperformed those acquiring it as a first language at the same age.
• First-language ASL acquisition performance declined with increasing age of acquisition.
• Deficits were most pronounced in lexical identification, grammatical acceptability, and memory for sentence meaning, not in fine-motor or pattern segmentation skills.

Conclusions:

• Acquiring American Sign Language (ASL) as a second language after childhood leads to superior outcomes compared to first-language acquisition initiated later.
• These findings challenge traditional views of critical periods for language acquisition, suggesting plasticity beyond early childhood.
• Age of acquisition significantly impacts specific aspects of sign language processing, particularly those involving complex linguistic and memory functions.