A new hypothesis about late second language learning: What bilingualism teaches us about the mind and the brain

By Judith F. Kroll

An enduring question about late second language (L2) learning is why there are apparent constraints on the ability of adult learners to understand and speak the L2. Past research suggests that these constraints reflect characteristics of adult learners and the nature of the language learning contexts available to them. We propose a new hypothesis that shifts the focus to consider how a model of proficient adult bilingualism may provide new insights into late L2 learning. The critical observation is that proficient bilinguals are not monolingual-like in their native language. The new hypothesis is that successful adult L2 learners are individuals who are able to effectively change the native language to accommodate the L2 and to negotiate the cross-language competition that characterizes proficient bilingualism. The hypothesized changes may involve processing costs that initially slow the native language and make performance more error prone, make learners less sensitive to some features of the native language, and that open the native language to the influences of the L2. We review evidence from studies of language processing and brain imaging in bilinguals and L2 learners. High levels of cognitive resources and immersion in the L2 may enhance successful learning but what is hypothesized to be fundamental is change to the native language that functionally allows the L2 to develop as part of the language system.