Abstract

Adults’ ability to acquire the phonology of new languages (L2 learning) is subject to –sometimes persistent– limitations (though there is individual variability). One common explanation for these limitations involves maturational effects, such as reduced plasticity of the adult brain. Another common explanation emphasizes the role of native language (L1) influence on L2 learning. Drawing on normed proficiency assessments of around 50,000 L2 Dutch learners from 62 L1 backgrounds, we investigate the effects of L1-to-L2 similarity in phonology on L2 Dutch proficiency (measured in terms of the number of new features of each new L2 sound). We do so while simultaneously controlling for –among other variables—age of acquisition, length of exposure, and their interactions with L1-to-L2 phonological similarity (via multilevel regression). We find that L2 proficiency increases with younger age of acquisition, longer exposure, and increasing L1-to-L2 phonological similarity. Additionally, the effect of L1-to-L2 phonological similarity interacts with age of acquisition and length of exposure, such that transfer from L1 to L2 a) becomes stronger the later in life the L2 is acquired, and b) weaker with increasing exposure to the L2. That is, we find that L1 has a continued influence on L2 phonological learning. This influence is stronger when the learner had more experience with L1 (later age of acquisition of L2) and decreased as experience with L2 increases. Taken together, these three properties of L2 learning support experienced-based accounts that emphasize the continued role of prior language experience in L2 learning, and specifically, the pivotal role of similarity-based transfer.