the speakers of Swedish, who had either maintained their first language (L1) (immigrants) or had lost it (international adoptees), using native speaker controls. Through this design, we sought to disentangle the effects of the maturational state of the learner on L2 development from the effects of L1 interference: if additional language development is indeed constrained by an interfering L1, then adoptees should outperform immigrant speakers. The results of an auditory lexical decision task, in which fine vowel distinctions in Swedish had been modified, showed, however, no difference between the L2 groups. Instead, both L2 groups scored significantly lower than the native speaker group. The three groups did not differ in their ability to discriminate non-modified words. These findings demonstrate that L1 loss is not a crucial condition for successfully acquiring an L2, which in turn is taken as support for a maturational constraints view on L2 acquisition. A video abstract of this article can be viewed at: [ABSTRACT FROM AUTHOR]