Age-related effects in adult second language acquisition: A study of Mandarin-speaking learners of English

One of the assumptions, of the critical period hypothesis (Lenneberg, 1967) as interpreted by Bialystok and Hakuta, (1994) is that there should be no continuing age effect in second language (L2) acquisition after maturity at puberty: that is, there should be no systematic age-related differences in 12 proficiency outcomes among adult learners. In this thesis, I examine this assumption by comparing the oral L2 proficiency of two different age-of-arrival (AOA) groups: one group of 15 learners whose AOA in Canada was between 25 and 35, and another group of 15 learners whose AOA was between 40 and 55. AD were female Mandarin-speaking learning English as a second language. The two AOA groups were similar in terms of length of residence in Canada and years of first language (L1) education, but the later AOA group had the advantage of receiving more English instruction than the earlier AOA group since their arrival in the L2 environment. These adult learners were tested for accuracy of production of six basic morphosyntactic features of English via two speech tasks: an elicited imitation test and a guided oral interview. Excerpts taken from all of the guided oral interviews were also rated for fluency in English. Results demonstrated consistent advantages for the earlier arrivals over the later arrivals on the two summary measures of morphosyntactic accuracy on the measure of oral fluency, although this effect of AOA did not appear on every morphosyntactic feature tested. The overall results indicate that among these adult learners, differential L2 proficiency outcomes continue, as in prepubertal learning, to be related to learners' AOA in the L2 environment, thus posing an empirical challenge to the assumption implied by the critical period hypothesis.; A further comparison of the two AOA groups on the measures of learner variables that may underlie the effect of AOA on L2 proficiency outcomes highlights the importance of fluid intelligence, variety of L2 contact, and amount of L2 daily use. On these learner variables, which correlated positively with learners' L2 proficiency outcomes, the earlier AOA group had an advantage over the later one. Finally, the learners' account of their experiences and perceptions of learning English as a second language reveals the complexity of adult L2 acquisition, which involves factors pertaining not only to the learners themselves, but also to the social context in which the L2 is learned.