隨著全球化的演變，針對移民者及雙語現象的研究越來越多。其中語言學的關鍵期假說及母語與外語的干涉仍然是充滿爭議的研究議題。欲實驗關鍵期假說與外語的干涉的研究議題，本研究由兩大部分組成：英語母音及華語母音之研究，並且由三十位來自北加州的華語為母語之前中後期移民者來擔任受試者。
試驗性研究的研究目標就是比較移民英語系國家的早和晚，是否影響英文母語及中文母音的發音表現。由於受試者由男和女而組成，本實驗藉由巴克值轉換公式 (Traunmüller, 1990) 讓男女受試者的元音標準化，另外再藉由多邊形面積公式計算出前中後期移民者母音口腔面積的差異。
本實驗結果顯示，前中後期移民者在英語母音圖和母音口腔面積上有明顯的差異，中文母音圖和母音口腔面積上則無明顯差異。早期移民者於英語有明顯梯形母音圖，並且於母音口腔面積有隨著前中後期移民者而由大變小的趨勢，表示早期移民者的英語母音的發音表現較接近英語母語者且相較於中期及後期的移民者有較大的母音口腔面積，暗示著不同年齡於學習第二語言的表現上確實有明顯不同。而身為中文母語者，前中後期移民者於中文母音圖的表現無明顯不同，且皆為明顯梯形母音圖，暗示著學習第二語言的早晚並不影響第一語言的表現。最後，本實驗發現英語及中文的口腔母音面積有呈現反比現象，暗示著第二語言及第一語言有互相牽制的情形。

With globalization, studies of immigration and bilingualism increase. The question of the critical period and L1-L2 influences in second language acquisition remain disputed. This is an age-related study for testing the effects of age of arrival when Taiwanese immigrants living in a predominantly English-speaking environment. The study compares the English vowel productions within early, middle and late Mandarin-speaking immigrants of 30 participants from North California.
We normalized formant structures of English and Mandarin vowels produced by both female and male Mandarin-speaking immigrants by using Bark scale (Traunmüller, 1990) so we can see the transition by early, middle, and late immigrants without gender issue. Surveyor’s Area Formula (Braden, 1986) was also applied in the study to calculate the area of the vowel space of English and Mandarin by early, middle and late Mandarin-speaking immigrants to see the difference between two languages.
The results reveal that the early Mandarin-speaking immigrants demonstrated a clear trapezoid in their vowel chart, suggesting that their English vowel production should be more native-like than the rest. The surveyor’s area of English was bigger in the early Mandarin-speaking immigrants than in the middle and late Mandarin-speaking immigrants. As for the Mandarin vowel production, all of the three groups demonstrate no clear difference with clear trapezoid in their vowel chart, suggesting that the age of onset of learning L2 does not affect the performance of the L1. However, comparing the surveyor's area of English and Mandarin, we found an inverse relationship between the English and Mandarin vowel space area. This may imply that L1-L2 have somewhat interference in process of the language learning.

Aoyama, K., Flege, J., Guion, S., Akahane-Yamada, R., & Yamada, T. (2004). Perceived phonetic dissimilarity and L2 speech learning: the case of Japanese /r/ and English /l/ and /r/. Journal Of Phonetics, 32(2), 233-250. doi: 10.1016/s0095-4470(03)00036-6
Baker, W. (2004). The Interaction of the Bilingual’s Two Phonetic Systems: Differences in Early and Late Korean English Bilinguals. International Symposium on Bilingualism, ed. James Cohen, Kara T. McAlister, Kellie Rolstad, and Jeff MacSwan, 163-174. Somerville, MA: Cascadilla Press.
Baker, W., & Trofimovich, P. (2005). Interaction of Native- and Second-Language Vowel System(s) in Early and Late Bilinguals. Language And Speech, 48(1), 1-27. doi: 10.1177/00238309050480010101
Baker, W., & Trofimovich, P. (2006). Perceptual paths to accurate production of L2 vowels: The role of individual differences. IRAL – International Review Of Applied Linguistics In Language Teaching, 44(3). doi: 10.1515/iral.2006.010
Bialystok E. (2001). Bilingualism in development: Language, literacy and cognition. New York, NY, US: Cambridge University Press.
Braden, B. (1986). The Surveyor's Area Formula. The College Mathematics Journal, 17(4), 326-337. doi: 10.1080/07468342.1986.11972974
Chen, P-Y. (2018). Vowel Perception and Production by EFL Students in Taiwan. (MA.), National Chengchi University in Taiwan.
Chen, Y., Robb, M., Gilbert, H., & Lerman, J. (2001). Vowel production by Mandarin speakers of English. Clinical Linguistics & Phonetics, 15(6), 427-440.
Cook, V (1991). Second language learning and language teaching. London: E. Arnold.
Derwing, T., Munro, M., Thomson, R., & Rossiter, M. (2009). The relationship between L1 fluency and L2 fluency development. Studies In Second Language Acquisition, 31(04), 533. doi: 10.1017/s0272263109990015
Flege, J. (1987). A Critical Period for Learning to Pronounce Foreign Languages? Applied Linguistics, 8(2), 162-177. doi: 10.1093/applin/8.2.162
Flege, J. E. (1995). Second language speech learning: Theory, findings, and problems. In W. Strange (Ed.), Speech perception and linguistic experience: Issues in cross-language research, 233-277.
Flege, J. E. (1995). The phonetic study of bilingualism. In G. Bloothooft, V. Hazan, D. Huber, J. Llisterri (Eds.) European Studies in Phonetics and Speech Communication (pp. 98-103). Utrecht: OTS.
Flege, J., Bohn, O., & Jang, S. (1997). Effects of experience on non-native speakers' production and perception of English vowels. Journal Of Phonetics, 25(4), 437-470. doi: 10.1006/jpho.1997.0052
Flege, J., Frieda, E., & Nozawa, T. (1997). Amount of native-language (L1) use affects the pronunciation of an L2. Journal Of Phonetics, 25(2), 169-186. doi: 10.1006/jpho.1996.0040
Flege, J. E. (2003). Assessing constraints on second-language segmental production and perception. In A. Meyer & N. Schiller (Eds.), Phonetics and phonology in language comprehension and production, differences and similarities (pp. 319- 355). Berlin: Mouton de Gruyter.
Hu, R. (2016). The Age Factor in Second Language Learning. Theory and Practice in Language Studies, 6(11), 2164. https://doi.org/10.17507/tpls.0611.13
Jeng, J-Y. (2011). Yuyin shengxue-shuohua shengyin de kexue. Taipei: Psychological Publishing.
Krashen, S., Long, M., & Scarcella, R. (1979). Age, Rate and Eventual Attainment in Second Language Acquisition. TESOL Quarterly, 13(4), 573. doi: 10.2307/3586451
Lai, Y.-h. (2010). English vowel discrimination and assimilation by Chinese-speaking learners of English. Concentric: Studies in Linguistics, 36(2), 157-182.
Liao, J.-S. (2006). English vowel production of mandarin speakers. (Ph.D.), The University of Texas at Austin, Texas.
Lin, C. (2013). Perception and Production of English Front Vowels by Taiwanese EFL Learners. Theory And Practice In Language Studies, 3(11). doi: 10.4304/tpls.3.11.1952-1958
Long, M. (1990). Maturational Constraints on Language Development. Studies In Second Language Acquisition, 12(3), 251-285. doi: 10.1017/s0272263100009165
Mack, M. (1984). Early bilinguals: How monolingual-like are they? In M. Paradis & I. Lebrun (Eds.), Early bilingualism and child development. Lisse, The Netherlands: Swets & Zeitlinger.
Mack, M. (2003). The phonetic systems of bilinguals. In M. Banich & M. Mack (Eds.), Mind, brain, and language: Multidisciplinary perspectives (pp.309–349). Mahwah: Lawrence Erlbaum Press.
Odlin, T. (1989). Language Transfer: Cross-Linguistic Influence in Language Learning (Cambridge Applied Linguistics) (1st ed.). Cambridge University Press.
Piske, T., MacKay, I., & Flege, J. (2001). Factors affecting degree of foreign accent in an L2: a review. Journal Of Phonetics, 29(2), 191-215. doi: 10.1006/jpho.2001.0134
Praat: Doing Phonetics by Computer. (2011). Ear & Hearing, 32(2), 266. doi: 10.1097/aud.0b013e31821473f7
Piske, T., MacKay, I. R., & Flege, J. E. (2001). Factors affecting degree of foreign accent in an L2: a review. Journal of Phonetics, 29(2), 191–215. https://doi.org/10.1006/jpho.2001.0134
Pallier, C. (2003). Brain Imaging of Language Plasticity in Adopted Adults: Can a Second Language Replace the First? Cerebral Cortex, 13(2), 155–161. https://doi.org/10.1093/cercor/13.2.155
Paradis, M. (1993). Linguistic, psycholinguistic, and neurolinguistic aspects of "interference" in bilingual speakers: The activation threshold hypothesis. International Journal of Psycholinguistics, 9(2)[26], 133–145.
Patkowski, M. S. (1990). Age and Accent in a Second Language: A Reply to James Emil Flege. Applied Linguistics, 11(1), 73–89. https://doi.org/10.1093/applin/11.1.73
Penfield, W., & Roberts, L. (1959). Speech and brain mechanisms. Princeton: Princeton University Press.
Pickett, J. M., & Morris, S. R. (2000). The Acoustics of Speech Communication: Fundamentals, Speech Perception Theory, and Technology. The Journal of the Acoustical Society of America, 108(4), 1373–1374. https://doi.org/10.1121/1.1289701
Piske, T., MacKay, I. R., & Flege, J. E. (2001). Factors affecting degree of foreign accent in an L2: a review. Journal of Phonetics, 29(2), 191–215. https://doi.org/10.1006/jpho.2001.0134
Richard G. (1999). A Global Perspective on Bilingualism and Bilingual Education. CAL Online Resources: Digests. Carnegie Mellon University.
Tsimprea, J. M. (2017). Bilingualism and its Effect on Foreign Language Learning. American University in Dubai.
Traunmüller, H. (1990). Analytical expressions for the tonotopic sensory scale. The Journal of the Acoustical Society of America, 88(1), 97–100. https://doi.org/10.1121/1.399849
Yang Chen, Michael Robb, Harvey Gil. (2001). Vowel production by Mandarin speakers of English. Clinical Linguistics & Phonetics, 15(6), 427–440. https://doi.org/10.1080/02699200110044804