A Brief Literature Review and Self-reflection on the Critical Period Hypothesis
Introduction
Is there really an ideal age at which second language learning should begin? Is there only a slim chance for an adult learner to master a second language? These thought-provoking questions arising from the Critical Period Hypothesis, as well as the interesting phenomena relating to the hypothesis that occurred during my life as a teacher make it the focus of discussion of the essay.
The Critical Period Hypothesis: A highly debatable issue
One prominent proponent of the Critical Period Hypothesis (CPH) was Eric Lenneberg (1967), who based his hypothesis on neurological development. He explained that there is a maturation process called cerebral lateralization, during which the brain loses its plasticity as it gradually matures.
This process, starts at around two, is supposed to be completed at puberty, after which it is very difficult or even impossible for a learner to successfully acquire a new language. The CPH has been widely discussed in the area of second language acquisition (SLA) and has aroused much controversy.
The CPH is most closely linked to the acquisition of the phonological system. As put forward by Scovel (1988), it is not possible for learners beyond the age of 12 to attain a native-like pronunciation though they might be able to master the syntax and vocabulary of a second language.
A similar view regarding phonological attainment was propounded by Flege and Fletcher (1992, p.385). They concluded from their studies that ‘a foreign accent first emerges at an age of L2 learning of between 5 and 8 years’, which probably implies, in the domain of phonology, that the ‘critical period’ ends even earlier than what Lenneberg proposed. This coincides with later studies conducted by Krashen (1973), who claimed that lateralization is completed at around age 5.

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Mark Patkowski (1980) conducted a study on how the age factor is related to the acquisition of linguistic features other than accent. The findings further supported the CPH as the results indicated that the age factor is very important in a sense that it limits the learner’s development of a native-like mastery of various linguistic features of a second language. Jacquline Johnson and Elissa Newport (1989) also carried out a study relating to the rules of English morphology and syntax and found that those earliest starters got the highest scores on the grammaticality judgement test.
Despite some clear evidence that supports the CPH, a remarkable research undertaken by Catherine Snow and Marian Hoefnagel-Ho_hle (1978) provided evidence against it. The findings revealed that both adolescent and adult learners could surpass the children learners by making enormous and rapid progress in a wide range of language knowledge. White and Genesee (1996) also revealed in a grammaticality judgement task that late starters are able to achieve near-native proficiency.
Robert Dekeyser (2000) done something along the line of Johnson and Newport and found that adult and children might have different way in learning language.
Insights gained from the CPH: A Self-reflection
Taking into account what I have explored from the literature review, I do believe that the evidence for CPH is somewhat mixed, especially when I reflected upon the L2 learners I taught in a secondary school in Hong Kong. In all my years of teaching, I have had a chance to teach a fairly large number of L2 learners who are immigrants from the Mainland. They are of diverse backgrounds in terms of age, gender, financial condition, etc.
Very importantly, not all of them started learning English at the same age. There are a few cases which impressed me most. Two girls who first came to Hong Kong at the age of 17 joined my S4 class. Both of them started learning English at the age of around 12 when they were in the mainland. What was so remarkable was that both of them could write very fluently with highly accurate grammar and a variety of sentence patterns. Their performance in writing and reading even surpassed their local counterparts who started taking up English in kindergarten.
This can somewhat be taken as counter-evidence to the CPH. Both girls revealed that they had an extraordinary strong motivation to improve their English and to catch up with their classmates. These social-psychological factors did play a part in their success of L2 acquisition. As discussed in Lightbown (2006), learners beginning at primary school level might not have an absolute advantage over adolescent learners in attaining greater proficiency in the long run.
This is especially true when learners, confining to a classroom setting, receive just a few hours of training every week. Interesting enough, despite extra tutorials to improve the girls’ oral skills, they carried a rather strong foreign accent. In fact, they do speak Cantonese (a different dialect) with an accent, let alone English, a language which is far different from their mother tongue. This seems to support findings demonstrating that it is very unlikely for late starters to attain native-like pronunciation.
Conclusion
As an experienced and sensible teacher, I believe that one should not constrain ourselves too much in any one of the theories or models. If a teacher is a true believer of the CPH, it would somehow affect their expectation on their students who are beyond the puberty period. This in turn would also lead to a lower expectation of the students themselves even though they are not aware of the fact that their teachers assume that they have already gone beyond the optimal period of learning a second language.
Instead we should be flexible and reflective enough to cater to our learners’ needs and facilitate their learning regardless of their age. Though I am convinced that the age factor does play a part in affecting SLA, I concern more in how I could adjust my teaching methods to suit the needs of learners at different ages.
It is no doubt that the hypothesis should not be oversimplified and overgeneralized and to be indiscriminately applied to our students because second language learning is a really complicated process in which a lot of factors can be intermingled to affect how successfully a person can learn a second language.
To conclude, there has been no overwhelming evidence showing that young learners have absolute superiority over their adult counterparts. Despite the difference in the research findings, there seems to be a general consensus that there are a number of factors interacting to affect SLA, and it is possible that late learners might achieve success in SLA, most likely via a different route from children learners, as discussed by Krashen (1975); (Dekeyser 2000). I believe it is also due to this reason that a lot of other factors cognitive, psycholinguistic and socio-cultural that come into place as to how a learner acquire a second language.
References
Lightbown, P. & Spada, N. (1993). How Languages Are Learned. Oxford University Press
Robertson, P. (2002) The Critical Age Hypothiseis, The Asian EFL Journal (On-Line) http://www.asian-efl-journal.com/marcharticles_pr.php
Flege, J.E. and Fletcher, K.L. 1992, talker and listener effects on degree of perceived foreign accent. Journal of the Acoustical Society of America 91, 370-89.
Daniels, D. and Moos, R.H. (1990). Assessing Life Stressors and Social Resources among Adolescents: Applications to Depressed Youth. Journal of Adolescent Research, 5, 268-289.
Erikson, Erik H. (1980). Identity and the life cycle. W.W. Norton & Company, Inc.
Hall, J.A. (1987). Parent-Adolescent Conflict. An Empirical Review. Adolescent, 22, 767-789.
Montemayor, R. (1986). Family Variation in Parent-Adolescent Storm and Stress. Journal of Adolescent Research, 1, 15-31.
Ormrod, J.E. (2000). Educational psychology: developing learners (3rd ed.). London: Prentice Hall.
Rice, F.P. (1993). The adolescent: Development, relationships, and culture (7th ed.). Boston: Allyn and Bacon.
The concept of critical period was initially introduced by Wilder Penfield and Lamar Roberts (1959). As summed up by Hong and Morgan (2005), they proposed that the relatively higher plasticity of a child’s brain, as compared to that of an adult, enables a child to learn a language more easily.