The relatively recent insight, that the ultimate attainment of childhood L2 learners does not always – or, in fact, not very often – converge fully with chat of native speakers, has called into question age of acquisition (AoA) as the cause of such near-native (rather than nativelike) ultimate attainment. An alternative, increasingly cherished (admittedly theoretically intriguing) interpretation is that the subtle differences between near-native and nativelike language knowledge and behavior arise, not as an effect of AoA, but merely as an artefact from the customary, allegedly biased comparison between monolingual and bilingual speakers. Along a similar line of thought, it is commonly held that it is the monolingual acquisition (made possible through total L1 loss and ‘neural resetting’) that makes it possible or internationally adopted children to become fully nativelike in their L2 (or “new L1”). With data from a large-scale 2×2 factorial/crossed-design study, we challenge these views. Eighty adult speakers of Swedish, who were either L1 monolinguals (‘crib monolinguals’), L1 (simultaneous) bilinguals (‘crib bilinguals’), early L2 (sequential) monolinguals (‘childhood adoptees’), and early L2 (sequential) bilinguals (‘childhood immigrants’), were tested on 13 measures of language representation and processing in Swedish, covering both production and perception of phonetics, morphosyntax, and lexis. The results show robust and consistent effects AoA but next-to-negligible effects of bilingualism on ultimate attainment (and only on two lexical measures), suggesting that AoA – not bilingualism – is the primary determinant of L2 ultimate attainment.

Niclas Abrahamsson is a full professor in Swedish as a Second Language and the director of the Centre for Research on Bilingualism at Stockholm University. The central concerns of his research and teaching include linguistic (especially phonetic and phonological), psycholinguistic (including neuro-cognitive), and psychological aspects of SLA/bilingualism. A recurrent theme is child-adult differences in language acquisition and loss and their relation to the maturation of the brain and so-called critical periods. His current research program includes (1) age of acquisition effects vs. bilingualism effects, (2) the roles of procedural/implicit vs. declarative/explicit memory in near-native grammatical acquisition and processing, and (3) listeners’ perception of non-native speech.