Essay Examples - Language Acquisition and the Critical Period Hypothesis

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In the field of applied linguistics the topic of critical period hypothesis (CPH) has proved significant. One principle reason is the assertion by various researchers that second language acquisition (SLA) is more easily obtained by younger children. Subsequently, the study of CPH has been instrumental in the formulation of teaching methodologies for foreign language acquisition (Scovel, 2000). The purpose of this paper is to carefully examine the origination of the CPH and its subsequent impact on primary language learning (L1) and secondary language acquisition (L2). In addition to age, other relevant independent variables affecting development of L1 and L2 include sociological, psychological, and physiological factors (Schouten, 2009).


The critical period hypothesis is identified as the capacity to obtain language relative to age. Specifically, (CPH) purports that language attainment should occur within a certain time frame, which is understood as pre-puberty. Penfield and Roberts (1959) proposed the CPH hypothesis in connection with original language. Lenneberg (1967) expanded the concept to include the acquisition of a secondary language. Other studies indicated a direct correlation between secondary language learning, and the age of an individual.

It was determined that prior to puberty there is a gradual decline in secondary language acquisition. For those individuals that are introduced to a secondary language at a very young age (i.e. 7-8), there is a greater aptitude for native-like attainment. In contrast, those adult learners seeking secondary language acquisition have noted difficulty in obtaining native-like competence.

Research suggests that while biological maturation may affect language acquisition other mechanisms play a significant role (Birdsong & Molis, 2001; Hakuta et al., 2003, Oyama, 1976). Native-like competence is understood as mastery of areas including phonology and syntax of the non-native language. According to Cook et al., as cited in (Scovel, 2000) any notable discourse on second language acquisition (SLA) over the past twenty years includes discussion of the CPH hypothesis.

Literature Review

The critical period hypothesis (CPH) is most closely attributed to and influenced by Lenneberg. Prior to Lenneberg, Canadian neurosurgeon Penfield (1963) first proposed the benefits of learning a language at an earlier stage of life. One of the stated benefits was the significant plasticity of a child’s brain development pre-puberty (Scovel, 2000). Scovel posited that Penfield’s impact on early stage second language acquisition includes influencing the formation of CPH and foreign language pedagogy. As a result of Penfield’s continued promulgation of early foreign language acquisition, Lenneberg a psycholinguist was prompted to continue the study of CPH (Scovel, 2000).

Lenneberg (1967) hypothesized a correlation between brain changes and the development of speech and language. As such, one objective was to determine the age in which language acquisition was no longer probable. Empirical evidence was obtained from aphasics, language development in the mentally disabled, and the onset of deafness in individuals of varying ages. Collectively the data indicated the existence of structural reorganization within the brain during the period of puberty (Schouten, 2009).

Although Lenneberg did not dismiss the notion of language development following puberty, he did indicate that language skills obtained would be underdeveloped. Therefore, he proposed that the critical period in which the brain would most proficiently obtain primary language, was between infancy and pre-puberty (Schouten, 2009).

Hakuta, Bialystock, and Wiley (2003) also sought to determine whether there was evidence of a critical period for language development, through observation of immigrants. Specifically they sought to ascertain whether or not there was a sharp decline in learning outcome around a particular age. They also wanted to ascertain whether any observed decline was independent from social or educational variables. Earlier research identified a significant impact on first language proficiency and second language attainment relative to age, specifically puberty. Collectively the literature reveals empirical data, which strengthens the argument introduced in the critical period hypothesis.

Other studies found a pattern of decline in language proficiency that was age related (Johnson and Newport 1989, 1991). However that data was inconclusive as age, the degree of exposure, social, and philological backgrounds were also influential variables (Bialystok and Hakuta, 1994). Johnson and Newport (1989) as cited in Schouten (2009), examined the correlation between maturation and the capacity of individuals to obtain a second language. Their objective was to conduct a study that would either validate or disprove the presence of age-related effects on second language attainment.

In their study there were forty-six native Chinese and Korean speakers that came to the United States between the ages of 3 to 39. These were all individuals who subsequently learned English as a second language. The group was tested on grammar competency of English language sentences (Schouten, 2009). The group was divided into four groups’, age 3-7, age 8-10, age 11-15, and age 17-39. The results indicated a discernible correlation between an individual’s age when they arrived in the United States and the test results.

The Johnson and Newport (1989) study produce similar data as earlier studies by Oyama (1978) and Patkowski (1980). In the earlier studies by Oyama and Patkowski evidence indicated that the one constant variable on comprehension of language structures was the age of an individual when they arrive in the United States. In the Johnson and Newport study those individuals exposed to the English language between the ages of 3 and 7 performed with native-like competency (Schouten, 2009). Those subjects between the ages 8 and 10 had relatively high scores but tested lower than the 3-7 age group. The groups that were first exposed during the ages of 11-15 had higher scores than the adult counterparts but lower scores than the 3-7 and 8-10 age groups. These results indicate that success in learning language is dependent upon the age of exposure (Schouten, 2009). An emergent question is what factors determine whether an individual has obtained native-like language acquisition.

Examining the critical period hypothesis from a fairly superficial yet observable perspective, is the role of phonology in language acquisition. A native speaker may conclude that language acquisition is limited if they observe a foreign sound in the pronunciation of the secondary language. Long (1990) and Patkowski (1994) argue that obtaining a native-like accent requires early exposure to the secondary language. This idea is further purported by Scovel (1988) as quoted in Schouten (2009), who proposes that pronunciation development within the critical period is most paramount. According to Scovel phonological mastery requires the development of neuromuscular skills.

In contrast to the CPH

In stark contrast some researchers completely rejected the notion of the critical period hypothesis. In those studies there were adult learners who obtained native-like competence of a second language. Such empirical data and the associated behavioral observations indicate that the critical period hypothesis is not absolute or without flaw (Epstein, Flynn & Martohardjono, 1996; Hakuta, 2001).

Studies exist that contradict the Johnson and Newport (1989) claim of second language acquisition being impossible beyond the critical period. For example White and Genesse (1996), conducted a study of 89 individuals who identified English as a second language (Schouten, 2009). The methodology of data acquisition included appraisal of elocution, morphosyntax, fluency, vocabulary choice, and comprehensive nativeness. The results of the study indicate that there are adult learners who have a language competence that is indistinguishable from native speakers (Schouten, 2009).

Another noteworthy study was that by Birdsong and Molis (2001) which revealed native-like language attainment by adults. Additionally Birdsong and Molis conducted a study that proved that the results of Johnson and Newport’s study were not universal. Although there was a similar methodology to that of Johnson and Newport, the principle language spoken differed. There was a substitution of Spanish speakers for Chinese and Korean first language speakers (Schouten, 2009).

In the study by Johnson and Newport, out of the forty-six participants 50 percent (23 individuals) who were exposed late had 92 percent accuracy on the grammar judgment test. In the Birdsong and Molis study 13 participants out of the 32 subjects (approximately 40 percent) received a 92 percent or higher grammar judgment test score. The variance in results proves that the Johnson and Newport results are not universal. Further, variant results contradict the notion that native-like language attainment is not solely influenced by maturation level (Schouten, 2009).

Slavoff and Johnson (1995) discovered no significant distinction between learners (7-9) and youth who were (10-12). This is significant because it challenges the traditional notion of variance in language acquisition related to maturity. The study also discovered that there were performance variations between boys and girls. In the study girls outperformed their male counterparts. Therefore, grammatical judgments as a measurement for determining native speaking competence should be carefully considered (Scovel, 2000).


In analysis of the variant views on the critical period hypothesis a reformulation is proposed. DeKeyser (2000) as quoted in Schouten (2009) proposes the existence of high-functioning adults related to language acquisition does not necessarily contradict critical period hypothesis. It simply requires a reexamination of the present framework of the critical period hypothesis. Further DeKeyser indicates that there are two types of mechanisms existent within human beings (Schouten, 2009). One type is the language-specific mechanism is the implicit learning which occurs during childhood. Language–specific mechanism is essentially the same in human beings. The other type of mechanism is general mechanisms of explicit learning. A general mechanism has variance from individual to individual. DeKeyser hypothesizes that although the critical period for implicit learning mechanism may have passed their general learning mechanism is still useful (Schouten, 2009).

This hypothesis was tested by replicating Johnson and Newport’s work, using fifty-seven Hungarian learners of English. The subjects were assessed for verbal aptitude through observation of morphosyntactic performance. One result of the study was a negative correlation between an individual’s maturity and initial exposure to English (Schouten, 2009). However, another result was that adult learners with high verbal propensity had greater native-like proficiency. Ultimately these results affirmed that while Johnson and Newport revealed the importance of language-specific mechanism within the critical period, general learning mechanisms didn’t require the same critical period (Schouten, 2009).


The purpose of this report has been to examine empirical data regarding the critical period hypothesis for secondary language acquisition. Cumulatively, the examined literature indicates that the critical period hypothesis is impacted by multiple factors. There are biological and social factors as well as evidence indicating the value of secondary language education. The earlier an individual receives formal education of secondary language, the more probable is the attainment of native-like language (Birdsong & Molis, 2001; Hakuta et al., 2003; Oyama, 1976). There are also extreme cases where isolation from normal social engagement can adversely impact a child’s normative development. Such is the case of Genie who at age 13 was unable to speak due to her father not allowing her to interact in healthy ways. When Genie was initially discovered her grammatical competency was comparative to a regular 5 year old. Although she was introduced to language at an age post-puberty she received supportive services to assist in language development (PapperZZ, 2011).

One of the supportive services Genie received was a language training program which allowed her to begin the development of vocabulary and language comprehension. However, acquiring syntax was not as easily obtainable. Another case study involves Victor a young many who in the 18th century was referred to as the wild boy of Aveyron (PapperZZ, 2011). From birth until approximately 12 years of age (puberty) he was living in the woods. One observed behavior when he was captured was that he could not speak. In fact, according to Ryan and Singleton (2004) he experienced periodic spasms. The spasms indicated an undesirable impact of stress associated with socialization that adversely impacted his nervous system (PapperZZ, 2011).

The case studies of Genie and Victor indicate the importance of appropriate exposure to an environment that supports normative linguistic development. Implicit within this understanding is the overall validity of certain principles within the critical period hypothesis. However, there are also indicators from other reviewed literature of other factors besides maturity that affect secondary language acquisition. Adult subjects with a high propensity to vocabulary were able to achieve native-like competency in secondary language. This would imply that secondary education is effective in language development. Additionally, it indicates that vocabulary and language comprehension requires a level of customization based on each individual’s aptitude.

In regards to secondary language acquisition (L2), researchers like (Flege et. al.,) as cited in Singleton (2001), indicate the value of cultural immersion in secondary language acquisition. In other words, regardless of age an individual should spend considerable time in the country where the target language is spoken. Additionally, there should be social engagement and interaction with those who are considered native speakers of the target language. Not only does this accelerate the learning process, it also addresses the issue of proper pronunciation of the native language. Within this approach is an awareness that L1 (primary language) and L2 (secondary language) may have some phonetic overlap. In other words an individual may not necessarily be able to distinguish between the phonetic sounds of L1 and L2 (Singleton, 2001).

Also, the effectiveness of the education is also paramount. If individuals are exposed at an early age to explicit language instruction then accelerated learning occurs. However, if language training is not part of the normative immersion experience then the language acquisition process is hindered. This is especially true in situations where an individual is seeking to learn L2. If they are an adult learner then the process of secondary learning is hindered even further.

Further research needs to examine the comparative analysis between post pubertal L2 beginners and those that obtain an L2 during their young years. Also, the examination of the role of maturation, social, education, gender, and other variables should be analyzed within different cultural contexts. This could include an examination of how L1 English speakers would respond in a foreign L2 environment. Most of the literature discussed in this report implies that the L2 language is English meaning the foreigners (Chinese, Spanish, etc.) have L1’s that don’t include English. In order for language acquisition principles to be accurate and transferable they need to produce similar results within a multiplicity of contexts.

The development of language acquisition whether referring to L1 or L2 is also critical to human development. Therefore, social engagement is a necessary behavior that is integral to the life of every human being. Re-examing the case of Genie reveals the psychological and biological impact of the physical abuse and lack of socialization by her father. If she made a sound the father would physically abuse her, which caused her to associate social engagement and language use with pain. According to subsequent brain scans her right brain was very significant. In contrast the left hemisphere due to infrequent use had not grown appropriately (PapperZZ, 2011).

Finally, there needs to be further examination on the significance of the critical period (before puberty) for language development. This could include the acquisition of vocabulary, and mastery of areas including phonology and syntax. Further, research should also indicate what social factors most significantly influence language development. Although the diminishing cerebral plasticity is something that is biological there are factors that can be influenced. By focusing on factors that can be properly managed and influenced, secondary language acquisition is probable for those that desire it.


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Epstein, S., Flynn, S., & Martohardjono, G. (1996). Second language acquisition: Theoretical and experimental issues in contemporary research. Behavioral and Brain Sciences, 19, 677–758.

Hakuta, K., Bialystok E. & Wiley, E. (2003).Critical Evidence: A test of the critical-period hypothesis

Johnson, J. S., & Newport, E. L. (1991). Critical period effects on universal properties of language: The status of subjacency in the acquisition of a second language. Cognition, 39, 215–258.

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Oyama, S. (1976).A Sensitive period for the acquisition of a nonnative phonological system. Journal of Psycholinguistic Research. 5, 261-283.

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Penfield, W., & Roberts, L. (1959). Speech and brain mechanisms. Princeton, NJ: PrincetonUniversity Press.

Schouten, A. (2009). The Critical Period Hypothesis: Support, Challenge, and Reconceptualization. Tesol and Applied Linguistics, 9(1), 1-16.

Scovel, T. (2000). A Critical Review of The Critical Period Research. A Critical Review of the Critical Period Research, 1(20), 213-223.

Singleton, D. (2001). Age and Second  Language Acquisition. Annual Review of Applied Linguistics, 1(21), 77-89.

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