A Test of the Critical-Period Hypothesis for Second-Language Acquisition free essay sample

The analyses tested a key prediction of the hypothesis, namely, that the line regressing second-language attainment on age of immigration would be markedly different on either side of the criticalage point. Predictions tested were that there would be a difference in slope, a difference in the mean while controlling for slope, or both. The results showed large linear effects for level of education and for age of immigration, but a negligible amount of additional variance was accounted for when the parameters for difference in slope and difference in means were estimated. Thus, the pattern of decline in second-language acquisition failed to produce the discontinuity that is an essential hallmark of a critical period. The idea that there is a biologically based critical period for secondlanguage acquisition that prevents older learners from achieving nativelike competence has appeal to both theorists and social policymakers (Bailey, Bruer, Symons, Lichtman, 2001). The critical-period hypothesis was originally proposed in the neurolinguistic literature by Pen? ld and Roberts (1959) and vigorously followed up by Lenneberg (1967), who speculated that maturational aspects of the brain that limited recovery from brain traumas and disorders would extend to second-language acquisition. We will write a custom essay sample on A Test of the Critical-Period Hypothesis for Second-Language Acquisition or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Subsequent research using behavioral evidence appeared to con? rm this hypothesis (Johnson, 1992; Johnson Newport, 1989; Oyama, 1976; Patkowski, 1980, 1994). The measure of language pro? ciency in these studies varied (ratings of oral speech, grammaticality judgment tasks), but the typical result was that pro? iency scores declined with increases in age of initial exposure to the second language. The claim that there is an age-related decline in the success with which individuals master a second language is not controversial. The diminished average achievement of older learners is supported by personal anecdote and documented by empirical evidence (Flege, YeniKomshian, Liu, 1999; Stevens, 1999). What is controversial, though, is whether this pattern meets the conditions for concluding that a critical period constrains learning in a way predicted by the theory. A critical period minimally entails two characteristics: (a) a high level of preparedness for learning within a speci? ed developmental period to ensure the domain is mastered by the species and (b) a lack of preparedness outside this period (Bornstein, 1989; Colombo, 1982). The consequence of these conditions is that the relation between learning and age is different inside and outside the critical period. Proponents of a critical-period explanation have attempted to place the description of second-language learning within these parameters. Johnson Address correspondence to Kenji Hakuta, CERAS Building, Stanford University, Stanford, CA 94305; e-mail: [emailprotected] edu. VOL. 14, NO. 1, JANUARY 2003 and Newport (1989, 1991) have argued, for example, that there is a strong age-related decline in pro? ciency for languages learned prior to puberty (de? ned as 15 years old) and random variation in achievement among individuals who are exposed to a second language later in life. Such developmental discontinuity at an identi? able maturational time would constitute support for the two conditions of a critical period. The data, however, are controversial because of the dif? culty in separating out the effects of age of initial exposure, duration of exposure, and social and linguistic backgrounds of the participants (see the analysis and critique of Johnson and Newport’s study in Bialystok Hakuta, 1994). Other researchers have argued that the evidence fails to support the interpretation that language-learning potential is fundamentally changed after a critical period (e. g. , Epstein, Flynn, Martohardjono, 1996; Hakuta, 2001). Two kinds of evidence have typically been used in these challenges. The ? rst is the identi? cation of older learners who achieve nativelike competence in the second language (Birdsong, 1992; Bongaerts, Planken, Schils, 1995; Ioup, Boustagui, El Tigi, Moselle, 1994). The second is behavioral evidence that fails to reveal a qualitative change in learning outcomes at the close of a critical period (Bialystok Hakuta, 1999; Bialystok Miller, 1999; Birdsong Flege, 2000; Birdsong Molis, 2001; Flege, 1999; Flege, Munro, MacKay, 1995; Flege et al. 1999). Whether such evidence is considered damaging to the critical-period hypothesis depends on the stringency of the criteria for de? ning the boundaries of the critical period (Birdsong, 1999; Harley Wang, 1997; Singleton Lengyel, 1995). Nonetheless, both weak and strong interpretations of the critical-period hypothesis require the demonstration of a signi? cant change in learning outcome, not merely a monotonic decline with age. Defense of the position that language learning is constrained by a critical period requires specifying the maturational stage at which languagelearning potential changes, and ideally the reason for the change. However, there has been little consensus about what age constitutes the critical point, and reasons for proposing different ages have rarely been offered. Researchers have variously claimed, for example, that the age at which the critical period terminates is 5 years (Krashen, 1973), 6 years (Pinker, 1994), 12 years (Lenneberg, 1967), or 15 years (Johnson Newport, 1989). An alternative to the critical-period hypothesis is that second-language learning becomes compromised with age, potentially because of factors that are not speci? c to language but nevertheless interfere with the individual’s ability to learn a new language. These might include social and educational variables that in? uence learning potential and opportunity, as well as cognitive aging that gradually erodes some of the mechanisms necessary for learning a complex body of knowledge, such as a new language. Among social factors, education has been most clearly demonstrated to in? ence second-language acquisition. Learners who arrive as immigrants at different ages have fundamentally different experiences, are exposed to qualitatively and quantitatively different samples of the new language, and have distinctly different opportunities for formal study of the language either directly or through other educational content (Bialystok Hakuta, 1994; Flege et al. , 1999). Flege and his colleagues have reCopyright  © 2003 American Psychological Society 31 PSYCHOLOGICAL SCIENCE Critical Period in Second-Language Acquisition Table 1. Regression of English pro? iency on education: Spanish- and Chinese-speaking immigrants Variable Intercept 5–8 years education Some high school High school graduate Some college Intercept 5–8 years education Some high school High school graduate Some college Note. R2 Parameter estimate 1. 7431 0. 2493 0. 7324 1. 0693 1. 7398 2. 0573 0. 3484 0. 8710 1. 1708 1. 4445 SE Chinese 0. 00417 0. 00624 0. 00586 0. 00548 0. 00451 Spanish 0. 00136 0. 00184 0. 00196 0. 00209 0. 00198 SS 96,590 884 8,659 21,071 82,450 1,796,840 28,171 154,633 244,933 417,988 F 174,334. 0 1,596. 0 15,628. 1 38,030. 6 148,813. 0 2,293,711. 0 35,961. 197,393. 0 312,664. 0 533,572. 0 p . 0001 . 0001 . 0001 . 0001 . 0001 . 0001 . 0001 . 0001 . 0001 . 0001 .4221 for Chinese-speaking immigrants and . 2622 for Spanish-speaking immigrants. ported complex effec ts of educational programs on second-language acquisition, and in one of their studies age-of-learning effects disappeared when education was controlled (Flege et al. , 1999). The second group of factors is the changes in cognition that occur with aging. Although critical periods have not been posited in most cognitive domains, there are nonetheless age-related changes in cognitive processing. Some age-related changes in cognitive processes relevant to language learning are decreased ability to learn paired associates (Salthouse, 1992), increased dif? culty encoding new information (Craik Jennings, 1992; Park et al. , in press; Rabinowitz, Craik, Ackerman, 1982), and reduced accuracy recalling detail as opposed to gist (Hultsch Dixon, 1990). Kemper (1992) pointed out that older adults’ second-language pro? ciency, like their ? rst-language pro? ciency, could also be affected by such factors as working memory capacity, cognitive processing speed, and attention. All these factors decline with age, and the decline is documented across the life span. Such a reduction in cognitive resources would surely affect the ability to learn a new language. Older learners would ? nd the task more dif? cult than younger ones, although no critical period would be involved. In the present study, we examined the effect of age of acquisition on second-language pro? ciency by studying a very large sample of second-language learners who covered a wide range of ages of initial exposure to English. Minimally, demonstrating a critical period would require ? nding evidence for a clear discontinuity in learning outcome around a speci? ed age. Moreover, this pattern would have to be independent of social or educational factors that also impinge on successful second-language acquisition. the full range of the parameters in the variables of interest could be investigated. For Spanish speakers, we used data from California, Illinois, Texas, and New York, four of the largest states, with large populations of Spanish speakers.