|Abstract: ||在習得及使用第二語時，幼童在語音上的表現多優於成人，外國口音往往出現於成人的第二語。本文主旨在於探討外國口音形成的原因及年齡不同所造成的差異。證據顯示腦部發展的生理因素不足以解釋外口音的發生。‘語音翻譯假設’和較早的‘對比分析假設’也只能提供片面的解釋。我們認為成人的語音能力不可因其母語及生理發展而加以設限；國口音的形成乃基於學習環境、認知、社會、及情感多方面因素之綜合影響。我們以古生(Krashen)的‘監測模式’(Monitor Model)所提出的理論架構，對這些綜合因素做出一個較完整的解說。基於以上的論說，本文最後對於外語教學提出數項建議。|
When acquiring and speaking a second language (L2), children often outperform adults in pronunciation, with adults' second language being more susceptible to the so-called "foreign accent". This article explores the several competing accounts of age difference in foreign accent. We challenge the longstanding "critical period" hypothesis, which imposes definite physiological, maturational constraints on L2 acquistion, and then deliberate Flege's "phonological translation" hypothesis along with the contractive analysis hypothesis, both of which attribute foreign accent to the negative linguistic interference of the first language (L1). We contend that, although physiological and linguistic factors do affect L2 performance, adults' ability, like children's, to acquire and speak an accent-free L2 should not be prejudged, that the presence of foreign accent in adulits' L2 may be largely due to a combination of environmental, cognitive, social and affective factors, and that Krashen's Monitor Model provides a comprehensive framework where these factors can be coherently related. Finally, in light of our deliberations, we consider some of their implications for teaching foreign languages.