The critical period hypothesis stipulates that the capability of an individual to master a language is confined in the years before puberty. According to critical period hypothesis, the ability to master a language normally disappears after puberty due to maturation of the brain. Critical period hypothesis was proposed by Penfield, Roberts and Lenneberg in the 1950s and 60s (Han, 2004). These scholars developed their hypothesis based on various types of evidence.
One of the evidence used by these scholars was that of abused and feral children, who developed to maturity without learning human languages during their childhood. The second evidence used was that of deaf children who stopped acquiring spoken language after adolescence. The fact that children suffering from aphasia showed better recovery than adults was also used as evidence by these scholars (Han, 2004).
Critical period hypothesis has continued to be one of the fiercely contested issues in cognitive science, and more specifically psycholinguistics. The available literature on CPH provides different views on the characteristics of this phenomenon. One of the divergent views on CPH questions the existence of the most favorable, sensitive, or a critical period of language acquisition.
The origin of CPH has also attracted different views, and the debate has been on whether CPH is brought by cognitive or maturational factors (Gass &, Selinker, 2001). However, modern literature has acknowledged that CPH plays an important role in the acquisition of first language. There is sufficient evidence that if humans do not acquire a language in early stages of development, they normally lose the capability of mastering languages. This particularly affects the grammatical aspects (Gass &, Selinker, 2001).
The evidence that supports CPH is scarce, but its proponents normally use analogies and theoretical reasoning like development of vision to support their claims. The time limit of CPH has also generated different views among scholars (Fuchs, 2007).
Linguists who refute the idea of CPH argue that the concept of CPH can be easily falsified. Opponents of CPH maintain that there are individuals who have been exposed to a first or second language after puberty (critical period), and have developed native-like competency. Many researches, for example, those conducted by White and Genesee (1996), Bialystok (1997), and Birdsong and Molis (2001), have refuted the idea of CPH (Birdsong, 2009).
The study by White and Genesee examined eighty nine individuals who spoke English as their second language. These subjects were evaluated based on vocabulary choice, morphosyntax, fluency and the extent to which their language skills resembled those of native speakers. The data collected were then used to determine whether a relationship existed between the ages at which an individual is first exposed to a language, and the level of language mastery (Birdsong, 2009).
The findings of this study provided these researchers with sufficient evidence to enable them refute the claims of CPH. Several participants in this study achieved almost native-like mastery of the English language, despite the fact that they were exposed to the language after the critical period. In addition, the study also demonstrated that participants’ performance in grammatical judgment, in terms of speed, accuracy and writing, was similar to that of native speakers (Jedynak, 2009).
However, opponents of CPH do not totally refute the fact that individuals who are taught a language when they are young, are likely to be more competent than those taught in their adulthood. According to White and Genesee, adults who achieved native-like mastery of the English language in the study were a proof that both adults and children possess similar language learning mechanisms. This contravenes the popular notion in CPH that after puberty (critical period), native mastery of a language is impossible (Jedynak, 2009).
Linguistic scholars have generally agreed that CPH starts in infancy and ends at puberty, and the chances of it occurring after puberty are slim. This conception is also supported by the general societal notion that children do posses certain inborn advantages when it comes to mastering languages. Scholars have provided varying definitions of CPH based on whether the language being acquired is a first or a second language (Schouten, 2009).
But the common assumption is that after puberty an individual can never develop native-like competency, especially in intonation and pronunciation. This assumption is based on the fact that when children become older, cognitive changes takes place in their brains that makes it very difficult for instinctive mastering of a language.
Magnetic imaging techniques used in modern researches have also shown that children process their language differently from adolescents. This finding is based on the region activated in the brain during language development in children (Schouten, 2009).
The influence CPH has on acquisition of a second language is a subject that has attracted different opinions in research dealing with second language. Those who claim that CPH does not play a role in the acquisition of a second language, have cited evidence that adults can develop native-like competency in a second language.
Proponents of CPH in mastering a second language have maintained that native mastery of a second language can only develop in young learners. This implies that critical period and maturational restrain also affect the acquisition of a second language. Recent studies focusing on the role of CPH in the acquisition of a second language have concentrated on the assumption that biological basis for the critical period does exist (Schouten, 2009).
One of the most significant studies on the role of CPH in the acquisition of a second language was that conducted by Johnson and Newport. In this research, forty six adult immigrants from Korea and China, who had arrived in the US at different ages, were studied. The subjects were then evaluated on morphosyntactic rules like past tense, making plurals, motion in particles, and order of words.
The findings of this research demonstrated that a strong correlation existed between the scores in the tests, and the age at which the participants arrived in the US. From these result, Johnson and Newport made a conclusion that a critical period for the acquisition of a second language does exist. However, recent researchers have refuted these findings by arguing that the evidence generated does not show diminishing relationship between age of exposure, and competency in the second language (Du, 2010).
CPH can hinder someone from developing target language mastery. This view is especially true from a nativist approach. Adult second language learners can acquire morphosyntactic competencies such as past tense, making plurals, motion in particles, and order of words. However, they can never achieve native-like intonation and accent (Du, 2010).
Conclusion
The influence CPH has on the acquisition of a first or second language is an issue that has attracted varied opinions among linguistic scholars. Proponents of CPH argue that CPH plays a critical role in the acquisition of both first and second languages, and children do posses special innate cognitive abilities in learning languages. On the contrary, opponents of CPH argue that both adults and children posses similar abilities when it comes to mastery of languages.
References
Birdsong, D. (2009). Second language acquisition and the critical period hypothesis: [August 1996… symposium entitled “New Perspectives on the Critical Period for Second Language Acquisition”]. Mahwah, NJ: Erlbaum.
Du, L. (2010). Assess the critical period hypothesis in second language acquisition. English Language Teaching, 3(2): 219-223.
Fuchs, A. (2007). The critical period hypothesis supported by Genie’s case. Munchen: Grin Verlag.
Gass, S. M., & Selinker, L. (2001). Second language acquisition: An introductory course. Mahwah, NJ: Lawrence Erlbaum Associates, Inc.
Han, Z. (2004). Fossilization in adult second language acquisition. Clevedon: Multilingual Matters.
Jedynak, M. (2009). Critical period hypothesis revisited: The impact of age on ultimate attainment in the pronunciation of a foreign language. Berlin Bern Bruxelles New York, NY: Lang.
Schouten, A. (2009). The critical period hypothesis: Support, challenge, and reconceptualization. Working Papers in TESOL & Applied Linguistics, 9(1): 1-16.