Risk of early language deprivation among deaf bilinguals with early signing experience: Evidence from American Sign Language basic word order and bilingual proficiency.

This study aims to examine the role of early signing input on the robust reliance on ASL basic word order by deaf adult ASL signers who are exposed to different types of signing (ASL versus signing systems, SS) by early childhood. We used a sentence-picture matching task involving transitive ASL sentences in subject-verb-object order with consistent or conflicting animacy cues. All signers with early ASL input (12 native signers, 12 non-native signers with early ASL) showed robust reliance on ASL word order and good bilingual skills, while 37.5% (6/16) non-native signers with early exposure to SS showed a weak representation of ASL basic word order along with lower bilingual proficiency. These results suggest that the critical period effects for syntactic development are not limited to severe deprivation but can also manifest when early language is insufficient. Early, rich, and consistent language input during early childhood is required for syntactic development.