DEVELOPMENT OF PHONETIC CATEGORIES

移民到北美并开始学习英语作为第二语言(L2)的时间越晚，他们产生和感知某些英语元音和辅音的准确性就越低，他们的总体外国口音倾向于越强，他们识别英语单词的难度就越大。这种影响通常被归因于一个关键时期的过去。这项研究将评估另一种说法，即言语学习模式(SLM)。SLM提出，年龄对二语语音的影响是由于第一语言语音系统的发展，而不是学习语音能力的下降。更具体地说，SLM提出，随着第一语言语音类别的细化，他们更有可能吸收第二语言的声音，从而阻止语音类别的形成，这是准确产生和感知语音所需的。第一个拟议的项目将检查最近移民到美国的西班牙本土成年人，他们每隔6个月在7年内移民一次。需要检验的假设包括：(1)随着特定英语发音能力的提高，外国口音的总体程度将会降低；(2)只有在感知某些英语声音的能力也有所提高的情况下，才会观察到音段发音的改善；(3)伴随着对英语声音感知的改善，或者在此之前，会发现英语和西班牙语发音之间的语音差异。另一个项目将调查240名意大利本土成年人，他们都有丰富的英语经验，但根据他们第一次接触英语的年龄(范围：10到30岁)而有所不同。SLM预测，意大利本土参与者的外国口音程度将在青春期结束时线性增加，然后趋于平稳。该模型还预测，外国口音的程度与两次知觉测试的分数之间存在显著的相关性。最后的项目将考察四组以意大利语为母语的人，他们根据首次接触英语的年龄和自我报告的母语(L1)使用情况而有所不同。八个实验将通过测试英语元音的产生和感知以及英语单词的识别来测试语音类别的形成。根据假设，早期的双语者会比晚期的双语者表现更好，而现在使用第一语言的人很少比那些继续频繁使用第一语言的人表现得更好。

The later immigrants arrive in North America and begin to learn English as a second language (L2), the less accurately they produce and perceive certain English vowels and consonants, the stronger their overall degree of foreign accent tends to be, and the more difficulty they may have recognizing English words. Such effects are usually attributed to the passing of a critical period. This research will evaluate an alternative account, that of the Speech Learning Model (SLM). The SLM proposes that age- related effects on L2 speech arise from the development of the L1 phonetic system, not a diminished ability to learn speech. More specifically, the SLM proposes that as L1 phonetic categories are refined, they become more likely to assimilate L2 sounds and thus to block formation of the phonetic categories needed for the accurate production and perception of speech sounds. The first proposed project will examine native Spanish adults who recently immigrated to the U.S. at 6-month intervals over 7 years. Among the hypotheses to be tested are that (1) Overall degree of foreign accent will decrease as the ability to produce particular English sounds improves; (2) Improvements in segmental production will be observed only if the ability to perceive certain English sounds has also improved; (3) Improvements in the perception of English sounds will be accompanied, or preceded by the detection of phonetic differences between sounds found in English and Spanish. Another project will examine 240 native Italian adults who are all highly experienced in English but who differ according to their age of first exposure to English (range: 10 to 30 years). The SLM predicts that the native Italian participants' degree of foreign accent will increase linearly to the end of adolescence, then level out. The model also predicts that a significant correlation will exist between degree of foreign accent and the scores obtained on two perceptual tests. The final project will examine four groups of native Italian speakers who differ according to their age of first exposure to English and self-reported native language (L1) use. Eight experiments will test for the formation of phonetic categories by examining the production and perception of English vowels, and the recognition of English words. By hypothesis, early bilinguals will outperform late bilinguals, and individuals who now use their L1 seldom will outperform those who continue to use their L1 frequently.