First language acquisition differs from second language acquisition in prelingually deaf signers: Evidence from sensitivity to grammaticality judgement in British Sign Language

Kearsy Cormier,Eleni Orfanidou,David Vinson,Adam Schembri

doi:10.1016/j.cognition.2012.04.003

Abstract

Age of acquisition (AoA) effects have been used to support the notion of a critical period for first language acquisition. In this study, we examine AoA effects in deaf British Sign Language (BSL) users via a grammaticality judgment task. When English reading performance and nonverbal IQ are factored out, results show that accuracy of grammaticality judgement decreases as AoA increases, until around age 8, thus showing the unique effect of AoA on grammatical judgement in early learners. No such effects were found in those who acquired BSL after age 8. These late learners appear to have first language proficiency in English instead, which may have been used to scaffold learning of BSL as a second language later in life.

Highlights

According to a hypothesis originally proposed by Lenneberg (1967), there is a critical period for acquisition of a first language (L1) – i.e., the first accessible language to which an individual is exposed, typically from birth – linked to neural plasticity which decreases as an individual grows older
The current study shows significant L1 age of acquisition effects in the grammatical judgement of deaf British Sign Language (BSL) signers, when age of acquisition is between birth and around 8 years of age
No such effects were found in deaf BSL signers who acquired BSL after age 8, for whom English was likely functioning as their first language and BSL as their second

Summary

Introduction

According to a hypothesis originally proposed by Lenneberg (1967), there is a critical (or sensitive) period for acquisition of a first language (L1) – i.e., the first accessible language to which an individual is exposed, typically from birth – linked to neural plasticity which decreases as an individual grows older. This hypothesis has been extended to apply to subsequent, second language (L2) acquisition. One well-known case is Genie, a child who was isolated for the first 13 years of her life After she was discovered and exposed to English at age 13, Genie exhibited better lexical than syntactic development and better comprehension than production. It is difficult to draw strong conclusions about language development from cases such as Genie, due to their extreme rarity, and because their isolation has broad consequences on all aspects of cognitive and social development, their linguistic development; any effects of age of language acquisition are confounded with these other variables (Curtiss, 1977; Skuse, 1988)

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