L1 activation during L2 processing is modulated by both age of acquisition and proficiency

It is well established that access to the bilingual lexicon is non-selective: even in an entirely monolingual context, elements of the non-target language are active. Research has also shown that activation of the non-target language is greater at higher proficiency levels, suggesting that it may be proficiency that drives cross-language lexical activation. At the same time, the potential role of age of acquisition (AoA) in cross-language activation has gone largely unexplored, as most studies have either focused on adult L2 learners or have conflated AoA with L2 proficiency. The present study examines the roles of AoA and L2 proficiency in L2 lexical processing using the visual world paradigm. Participants were a group of early L1 Afrikaans-L2 English bilinguals (AoA 1-9 years) and a control group of L1 English speakers. Importantly, in the bilingual group, AoA and proficiency were not correlated. In the task, participants viewed a screen with four objects on it: a target object, a competitor object whose Afrikaans translation overlapped phonetically with the target object, and two unrelated distractor objects. The results show that the L2 English group was significantly more likely to look at the cross-language competitor than the L1 English group, thus providing evidence of cross-language activation. Importantly, the extent to which this activation occurred was modulated by both L2 proficiency and AoA. These findings suggest that while these two variables may have been confounded in previous research, they actually both exert effects on cross-language activation. The locus of this parallel activation effect is discussed in terms of connectionist models of bilingualism.