This study examined the impact of a study abroad (SA) English program on English and native vowel production. Basque-Spanish bilingual adolescents were assessed on their vowel production in English, Basque and Spanish before the SA program, the day after the program was completed, and four months later. The results revealed that after the SA program, participants’ English vowels were acoustically closer to English norms, revealing the effectiveness of SA programs in improving English vowel pronunciation. Yet, four months later, these benefits had faded, showing that regular input and active language use are required to maintain accurate pronunciation. SA also had effects on native production: bilingual participants showed assimilatory acoustic drift in both their languages towards the English vowel system; the extent of this drift was negatively correlated with improvements in English pronunciation. However, four months later, participants showed a ‘return’ drift towards their native norms. The results also revealed that usage frequency and switching habits played a ‘protective’ role: Frequent switching in bilinguals made the dominant native language less vulnerable to foreign-language influence. Our results suggest that factors related to the frequency and circumstances of native language use are key to authenticity in native language production.

这项研究考察了海外留学（SA）英语课程对英语和母语元音产生的影响。在实施SA计划之前，计划完成后的第二天和四个月后，对巴斯克-西班牙双语青少年的英语，巴斯克语和西班牙语的元音产生情况进行了评估。结果表明，在SA计划之后，参与者的英语元音在声学上更接近英语规范，这表明SA计划在提高英语元音发音方面的有效性。然而，四个月后，这些好处逐渐消失，表明需要定期输入和积极使用语言来保持准确的发音。SA也对本地语言产生了影响：双语参与者显示出他们的两种语言向英语元音系统的同化声漂；这种漂移的程度与英语发音的改善呈负相关。然而，四个月后，参与者表现出向其原始规范的“回归”漂移。结果还表明，使用频率和切换习惯起着“保护性”的作用：双语者的频繁切换使占主导地位的母语不太容易受到外语影响。我们的结果表明，与母语使用的频率和情况有关的因素是母语制作中真实性的关键。双语者的频繁切换使占主导地位的母语较不容易受到外语影响。我们的结果表明，与母语使用的频率和情况有关的因素是母语制作中真实性的关键。双语者的频繁切换使占主导地位的母语较不容易受到外语影响。我们的结果表明，与母语使用频率和情况有关的因素是母语制作中真实性的关键。