Critical Period Hypothesis in Second Language Acquisition

Introduction

The Critical Period Hypothesis (CPH) holds that an individual can naturally develop a first language only before reaching puberty. If first language development does not occur before puberty, it is unlikely to occur at all. There is little doubt that young children have an inherent ability to learn language quickly, and there is a widespread belief that younger learners perform better.

With reference to the CPH, modern magnetic imaging techniques have revealed fundamental differences between the brains of young children and adolescents. The prevailing assumption is that young children can acquire a first language very quickly because they are born with a special intuitive capacity for language. However, once puberty is reached, this innate capacity begins to atrophy and more cognitive systems located in the brain start to take over. After the onset of puberty, it therefore becomes difficult for a learner to acquire native speaker intonation, competence, and pronunciation.

The underlying assumption of the CPH is a biological view of language development. This view holds that as young children grow older, a fundamental change occurs in their brains that makes it impossible for them to acquire languages with the same ease as in early childhood. Nevertheless, there is extensive debate about whether a critical period applies to subsequent, or second, language acquisition.

Review of Singleton (2005)

The objective of this paper is to summarize the research article titled "The Critical Period Hypothesis: A Coat of Many Colors" (Singleton, 2005). Additionally, this paper examines the sustainability of the CPH in order to assess its validity.

"The Critical Period Hypothesis (CPH) in essence contends that the ability to learn a language is limited to the years before puberty, after which, most probably as a result of maturational processes in the brain, this ability disappears" (Moskovsky, 2001, p. 1). Singleton (2005) provides a greater understanding of the CPH by referring to Penfield et al.'s (1959) assertion on the critical period (CP). While Lenneberg (1967) is often considered the father of the CPH, Penfield et al. (1959) is widely regarded as the proto-CP theorist. For the purpose of language learning, Penfield argued that the human brain progressively becomes rigid and less flexible as a child approaches the age of nine — the point at which language acquisition enters the second decade of life.

Lenneberg, on the other hand, argued that children deafened before the completion of their second year would not receive any facilitation for oral skills compared to congenitally deaf children. He further asserted that people who have lost their hearing could be trained in all the oral language arts. Lenneberg maintained that at the developmental stage, language acquisition could quickly advance past puberty, which is also the point at which the lateralization process is considered complete. He noted that injury to the right hemisphere in children could cause language acquisition disturbances — and that such injuries would cause greater disturbances in children than in adults.

With reference to L2 acquisition, Lenneberg asserted that language learning becomes blocked once a child reaches puberty. While young adults at this stage may retain the ability to learn a foreign language, it is not easy to overcome a foreign accent. Foreign language learning at this stage can typically only be achieved through labored and conscious effort. Despite his position, however, his argument is undermined by the impressionistic nature of his data, particularly given newer evidence revealing that language development begins from birth and that young adults can develop native speaker competence even after puberty.

Singleton (2005) addresses the ongoing debate about lateralization, noting that certain low-level phonological or phonetic functions may be completed within the first year of life. The sensorimotor cognitive structures underlying a child's early years may be represented in both hemispheres. The author further argues that phonetic and phonological functions are generally localized by puberty, while syntactic functions can be acquired later in life. Pyramidal cells that enhance phonetic and phonological acquisition develop only when a child reaches the age of six to eight, and authentic L2 accents can be developed at these ages.

Phonology, Lateralization, and Maturational Constraints

Singleton cites Scovel (1988), who argues that acquiring vocabulary is quite different from learning pronunciation, and that people exposed to an L2 after the age of twelve cannot become native speakers phonologically. Singleton also refers to Johnson and Newport (1989), who found that learning capacity gradually deteriorates and subsequently undergoes an abrupt decline after puberty.

Singleton (2005) further points to Hyltenstam and Abrahamsson (2003), who assert that children experiencing temporary hearing impairment in the first year of life due to middle-ear infection subsequently show deficits in phonetic perception and verbal memory. Based on this finding, the critical period for phonology and phonetics is considered to end at the twelfth month of infancy.

The author distinguishes pronunciation from other language domains, arguing that acquiring vocabulary and morphosyntax is fundamentally different from learning pronunciation. Those first exposed to an L2 at age twelve or later cannot achieve native speaker phonetics. Singleton (2005) further quotes Johnson and Newport (1989) in noting that the critical period generally ends progressively around the ages of six or seven. Evidence from the English attainment of immigrants in the United States indicates that the maturational phase can be achieved within seven years, and that the capacity to acquire a native L2 accent deteriorates markedly by age twelve. As Singleton (2005, p. 272) states, "The prerequisite for the acquisition of L2 morphology and syntax to native levels is exposure to the L2 before age fifteen."

For example, children experiencing general hearing impairment in the first year of life due to middle-ear infection typically show deficits in phonetic perception and verbal memory, confirming that the critical period for phonology and phonetics ends at the twelfth month of infancy. A concrete illustration of age effects comes from second language acquisition research involving French learners at university level, who could outperform elementary pupils in comprehension; however, "younger beginners' pronunciation was generally much superior to that achieved by older beginners" (Singleton, 2005, p. 275).

Conclusion

Children are efficient and fast at acquiring second languages; however, data also reveal that children learn new languages more effortlessly, though more slowly, with less speed than adults or adolescents. The misattribution fallacy involves crediting language proficiency outcomes to the brain, when in fact many adult second language learners have the ability to achieve native speaker proficiency but generally fail to commit the necessary energy and motivation required to reach that level. Marinova-Todd et al. (2000) agree that adults generally achieve lower levels of proficiency than younger language learners, but argue that the relevant attributes are contextual rather than biological.

Observers note that children are generally highly motivated, and that this motivation is associated with the pleasure of learning. Johnston (2002) supports this argument, stating that "young adults are in fact capable of attaining a native-like accent, which runs counter to the CPH." Johnston relates this claim to recent findings identifying thirty-three successful language learners aged 20 to 70, all of whom had acquired their target language after puberty — twenty learning Hungarian from a different first language background, and thirteen native Hungarian speakers learning English (Johnston, 2002, p. 8).

Based on this evidence, age is not the only intrinsic factor influencing language acquisition. Educational and maturational factors also contribute significantly. This claim opens the possibility of a revised hypothesis encompassing both "younger = better" and "adult = better" outcomes in different contexts. Singleton's (2005) own conclusion on the CPH is that it is misleading, "since there is a vast amount of variation in the way in which the critical period for language acquisition is understood — affecting all the parameters deemed to be theoretically significant and indeed also relating to the ways in which the purported critical period is interpreted in terms of its implications for L2 instruction" (p. 269).

This paper has summarized Singleton's (2005) article "The Critical Period Hypothesis: A Coat of Many Colors." Singleton reviews several studies by early proponents of the CPH who believed that children have a greater capability to acquire language than adults, and that children who begin learning a language after puberty cannot achieve native speaker competence or proficiency. However, more recent scholarship has revealed fallacies in the CPH, as research demonstrates that young adults can also develop native speaker competence.

Young children are typically able to acquire language more quickly than adults, but this advantage appears to be driven largely by motivational factors rather than exclusively biological ones. The attributes that favor early language acquisition are, on balance, contextual rather than purely biological. As such, the CPH as traditionally formulated overstates the role of biological maturation and underestimates the range of factors — motivational, educational, and environmental — that shape language learning across the lifespan. For a broader overview of how biological and environmental factors interact in development, see the Britannica article on language acquisition.

Hyltenstam, K., & Abrahamsson, N. (2003). Maturational constraints in SLA. In C. Doughty & M. H. Long (Eds.), Handbook of Second Language Acquisition (pp. 539–588). Malden, MA: Blackwell.

Johnston, R. (2002). Addressing the age factor: Some implications for language policy. Scotland.

Johnson, J. S., & Newport, E. L. (1989). Critical period effects in second language learning: The influence of maturational state on the acquisition of ESL. Cognitive Psychology, 21(1), 60–99.

Lenneberg, E. H. (1967). Biological Foundations of Language. New York: Wiley.

Marinova-Todd, S. F., Marshall, D. B., & Snow, C. (2000). Three misconceptions about age and L2 learning. TESOL Quarterly, 34(1), 9–31.

Moskovsky, C. (2001). The Critical Period Hypothesis revisited. Proceedings of the 2001 Conference of the Australian Linguistic Society.

Penfield, W., & Roberts, L. (1959). Speech and Brain Mechanisms. Princeton, NJ: Princeton University Press.

Scovel, T. (1988). A Time to Speak: A Psycholinguistic Inquiry into the Critical Period for Human Language. Rowley, MA: Newbury House.

Scovel, T. (2000). A critical review of the critical period research. Annual Review of Applied Linguistics, 20, 213–223.

Singleton, D. (2005). The Critical Period Hypothesis: A coat of many colors. Walter de Gruyter, 269–285.