Niclas Abrahamsson. Foto: Anna Persson
Niclas Abrahamsson. Foto: Anna Persson

A classic topic in the field of second language acquisition, and the cognitive sciences at large, concerns the role of age of acquisition (AoA) for nativelike attainment in a second language (L2). Ever since the concept of ‘critical/sensitive period(s)’ for language acquisition entered the arena more than 50 years ago, well over a hundred studies have sought to ferret out the effects that timing of exposure exerts on L2 acquisition, showing that child learners outperform adult learners in the long run.

As classic a topic as AoA effects is, it is also highly controversial, having instigated vigorous discussions throughout the decades. The debate has largely focused on the ultimate cause of age effects – that is, whether they are maturational, experiential, socio-psychological, cognitive etc. in nature – rather than on their actual existence. However, the fairly recent finding that even the ultimate attainment of childhood L2 learners most often does not converge fully with that of native speakers (see Abrahamsson & Hyltenstam, 2009) has called into question AoA as the cause of such near-native (rather than fully nativelike) attainment.

As an alternative explanation, it has been suggested that, rather than AoA, bilingualism (in the sense of either bilingual acquisition, bilingual use, or bilingual competence/cognition as such) accounts for the subtle non-native features of early-learner ultimate attainment – and, by inference, also the near-nativeness of exceptionally advanced adult L2 learners. This suggestion relates to the fact that most studies on nativelike attainment compare L2 speakers who have retained their first language (L1), and therefore are functionally bilingual, with native controls who are functionally monolingual, thus effectively confounding AoA effects with the “inevitable” effects of bilingualism.

The monolingual-bilingual comparison becomes particularly problematic in the light of findings suggesting that the linguistic behavior of bilinguals may differ from that of monolinguals (cf. the ‘bilingual lexical deficit’; e.g., Bialystok, 2017), and ultimately renders any observations on AoA effects inconclusive. Surprisingly, however, despite the various formulations of the notion of bilingualism effects, and despite the recurrent critique of the ‘monolingual bias’ in age studies (see, e.g., ‘the bi/multilingual turn in SLA’; Ortega, 2010, 2013), few studies have actually attempted to address this question empirically. Thus, while it is indeed an intriguing possibility that bilingualism, rather than AoA, underlies the subtle non-nativelikeness of many childhood (as well as exceptionally advanced adult) learners, this suggestion currently remains at the level of speculation due to the absence of solid empirical data.

The current study aimed to address this gap by assessing the relative impact of AoA and bilingualism on near-native L2 ultimate attainment. To achieve this, the study introduces a unique experimental design, in which the variables AoA at birth/after birth vs. monolingualism/bilingualism have been fully crossed.