"Yes, for all first language acquisition," answers Dr. Rachel I. Mayberry, Director of the McGill School of Communication Sciences and Disorders. In her presentation to the AAAS symposium on Critical Periods of Development: Evidence from Children with Hearing Loss to be held on Saturday, February 19, at 9:30 a.m., Dr. Mayberry will explain how she came to that conclusion by looking for the answer to two questions: does age affect the outcome of first and second language learning equally? Are the effects of age limited to spoken languages or are signed languages affected as well?
"The deaf population who uses sign language allows us to answer these questions because deaf individuals learn sign languages under highly heterogeneous circumstances," explains Dr. Mayberry.
In her AAAS presentation, she will summarize a series of three experiments looking at grammatical processing and comprehension of American Sign Language and English in groups of deaf signers and hearing, second-language learners of English. "The results show that there is a critical period for language acquisition that guides the acquisition of all first languages, be they spoken or signed," says Dr. Mayberry. "The key element of the critical period for language is that the child be exposed to and fully acquire a language in early childhood. Failure to acquire language in early childhood produces a permanent and highly compromised ability to understand any language for the remainder of the life span."