Critical Period Hypothesis in Language Acquisition

This assignment delves into the Critical Period Hypothesis in language acquisition. It examines how early exposure to a language can significantly impact first and second language learning. Research studies are analyzed to illustrate the hypothesis's role in shaping linguistic development, particularly for deaf individuals and those with speech impairments. The assignment emphasizes the importance of proper linguistic environments during crucial developmental stages.

Running head: PSYCHOLOGY
Psychology
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The Critical Period Hypothesis (CPH) has been a topic of controversy among the scholars
who study language acquisition and development. According to the critical period hypothesis,
individuals acquire native language during the first few years after the birth if they are
introduced to proper stimuli. During the critical period of an individual’s development if the
person is unable to grasp the first language acquisition then it is a possibility that the person will
not be able to fully develop their ability to talk properly especially their use of grammar will be
hampered. In several species, especially in humans during the critical period of development
certain experiences and stimuli lead to the behavioral and language development of an
individual. The following paragraphs will provide a detailed explanation of different theories
propounded by all the linguists, psychologists and other scholars on this topic.
In his book “Biological Foundations of Language” Eric Lenneberg said that human
acquisition of language was an instance of the biological development of a person and it was
acquired during the critical growth period beginning from the birth of an individual and ending
when the person reaches puberty (Birdsong, 2014). He also said that if any individual wants to
learn a different language within or after this period of time then for that a different method will
be required and the person will be able to learn the other language with much difficulty.
Lenneberg proposed a hypothesis that the critical or sensitive period of language development
stopped at the puberty when the cortical lateralization of the brain function was established after
brain formation or functioning reached its maturity (De Groot & Kroll, 2014). To support his
theory of critical period hypothesis Lenneberg provided three evidences, the first one said that
the children who were brought up in an environment of neglect and in abandonment they
developed no prominent language acquisition skill, especially their phonology as well as their
syntax use was affected. Second evidence was about the deaf children who were exposed to

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language at older age and their communication skills were affected. Finally, the children
suffering from brain damage or aphasia had better chances of recovery than the adults who
suffered from the same condition (Temprana et al., 2015). After Lenneberg’s book was published
several scholars conducted substantial research on this topic, all these studies concluded that
there is a certain sensitive period during the development of a human when one attains
acquisition of language chiefly the phonological and grammatical skills.
Wilder Penfield and Lamar Roberts were the first to suggest the concept of critical period
hypothesis they proposed that the concept of CPH is related to the decline of neural plasticity
according to the age of a person and this causes a person to face difficulties in learning a first
language (Rund, 2014). Another point related to CPH suggested by Penfield is that if an
individual suffers from malnutrition during the time of critical development period then the
neural plasticity of the person is affected. Both Penfield and Roberts concluded in their study that
a person could learn multiple languages until the age of nine (Luine, 2014). Another famous
linguist Noam Chomsky proposed the Nativist Theory in which he propounded that humans have
biological inherent ability of language acquisition and that every infant is born with LAD or a
Language Acquisition device, which is a hypothetical part of the brain responsible for speech or
language acquisition. Chomsky also provided another theory of “Universal Grammar” which
means that, there is a universal format of grammar which has been biologically incorporated in
the genes of an individual from birth and that help the person to form grammatical skills
automatically (Saxton, 2017). Eric Lenneberg later supported the studies of Chomsky and in his
book, “Biological Foundations of Language” and he added that till the age of 13 in an
individual’s brain language is present in both the hemispheres till the lateralization function takes
place after the brain reaches maturity (Guasti, 2017). Although other scholars who conducted

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their research on this topic supported Lenneberg’s claim of the critical period of language
acquisition but they did not support strongly his hypothesis, which involved the relation between
lateralization function of the brain and the end of sensitive or critical period. Stephen Krashen
challenged the theories of Lenneberg and Penfield he stated that the function of the brain begins
a lot before puberty and thus the CPH theory does not affect the language acquisition.
According to the behaviorist theories provided by Skinner the development of language
in children occurs with the influence of the environment in which they grow up, the individuals
learn language by repetition and practice (Birdsong & Vanhove, 2016). They follow the natural
method of trial and error and heed the responses they get from the people around them. O.
Hobart Mowrer also supported this theory; he also said that language is learned through the
method of imitation and positive and negative responses to the external stimuli.
Both the neural line of research and behavioral ones advocate that there is a certain
critical and sensitive period for acquisition of language. According to certain case studies on
children who were, either abused or kept in isolation from birth or was feral by nature showed
deficits in certain aspects of language like phonology, semantics, use of syntax and pragmatics.
One of such prominent case study involves the story of “American Feral Child” Genie, who
suffered severe levels of abuse and malnutrition from her birth throughout the critical period
(Birdsong & Vanhove, 2016). The authorities discovered her at the age of 13, as she was kept
away preventing her to interact with the society she did not develop the ability to talk and her
language lacked coherence. After she was discovered psychologists and language experts
conducted a great deal of research into her life and the circumstance in which she grew up, as she
grew up in total isolation it gave the experts a chance to study her condition in regard to the CPH
theory. Genie did not acquire any language at the time when she was discovered thus it gave the

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linguists and psychologists a chance to see whether the theories propounded by Chomsky,
Lenneberg, Penfield and others actually have some relevance or not. Within the first few months,
Genie was able to grasp quite a lot about non-verbal communication and after some more time
she developed certain social skills although she never mastered a proper first language
acquisition (Friedmann & Rusou, 2015). She only gained a limited control over the use of syntax
of a language and morphology. There is another example of a girl named Isabelle who lived with
her deaf and dumb mother for six and a half years, but in her case, when she was discovered by
the authorities, after a certain period of time she was able to learn a first language after sessions
of training provided by specialists.
In the cases of the children who have been raised in isolation it is a general observation
that the cognitive as well as the physical abilities of the individuals will be affected, but for the
individuals who are raised in a general social atmosphere, for them the relation between age and
exposure to linguistic environment can be examined. The physical aspect of the brain will not be
affected as such (Veríssimo et al., 2017). The various aspects of language are during the critical
period of development. After the birth of an individual upto 5 years this period is very crucial for
the development of phonological aspects and inputs of words through the infant’s ear.
Grammatical skills and syntax of a coherent sentence is learnt within 12 years, it is supposed
that the semantic aspect is not that much affected during the critical period, but in the case of
Genie she was unable to use proper syntax although she could adopt some of the vocabularies of
the language she was exposed to (Danesi, 2017). According to different scholars, the end of the
critical period varies from 5 (suggested by StephenKrashen) years to 15 (suggested by Johnson
and Newport).

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The theory of critical period hypothesis has also been associated with second language
acquisition, but it is not that well accepted. Second language acquisition is the process of
learning or adopting a different language than one’s native tongue (Gheitury, Ashraf & Hashemi,
2014). The process of first language acquisition is more of a natural development but that of a
second language requires a lot of practice and effort. The chances of learning a second language
always remain but certain aspects of learning the second language change with increase of age.
Certain observations has been made that when an adult learns a new language then the foreign
accent is quite prominent in the pronunciation and sometimes the grammatical skills are also
affected. According to Singleton and Lengyel there is no certain defined critical period of
learning a new language because the vocabulary of the second language is learned in a conscious
manner. The CPH of acquisition of second language involves two certain approaches; one is “use
it then lose it” which says that when a person becomes older the excessive nerve circuits used
while learning the L1 break down (Ren, 2017). The required neural circuits for first language
acquisition stay intact though. The second approach“ use it or lose it” states that when a person
starts to learn a second language from an early age then that language is continued throughout
the lifetime and the neural circuitry remains active for language learning, this is also known as
the “ exercise hypothesis”(Mehrgan, 2014). Some of the scholars like Robertson does not believe
that critical period hypothesis apply to L2 acquisition, according to him personal factors such as
the willingness to learn a language, motivation and other factors influence the learning process.
In the end, it can be said that, there are many sensitive periods for acquisition of native
language, the phonological aspect being the toughest one. The scholars analyzed several case
studies and after the theories were put to test on real life subjects, the conclusion was made that
language acquisition during the early stages of an individual impacts the function of the brain,

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which in turn affects the different aspects of language. Research conducted of the deaf also
suggests that early exposure to one’s native language can help a lot in the acquisition of a first
language. The individuals who have problems of speech, syntax and grammar, it has been
observed that they were exposed to proper linguistic environment at a later age.

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Reference List:
Birdsong, D. (2014). The Critical Period Hypothesis for second language acquisition: Tailoring
the coat of many colors. In Essential topics in applied linguistics and
multilingualism (pp. 43-50). Springer International Publishing.
Birdsong, D., & Vanhove, J. (2016). Age of second language acquisition: Critical periods and
social concerns. Lifespan perspectives on bilingualism. APA and de Gruyter.
Danesi, M. (2017). The neuroscientific perspective in second language acquisition research: A
critical synopsis. Lenguas modernas, (21), 145-168.
De Groot, A. M., & Kroll, J. F. (Eds.). (2014). Tutorials in bilingualism: Psycholinguistic
perspectives. Psychology Press.
Gheitury, A., Ashraf, V., & Hashemi, R. (2014). Investigating deaf students’ knowledge of
Persian syntax: Further evidence for a critical period hypothesis. Neurocase, 20(3), 346-
354.
Friedmann, N., & Rusou, D. (2015). Critical period for first language: the crucial role of
language input during the first year of life. Current opinion in neurobiology, 35, 27-34.
Guasti, M. T. (2017). Language acquisition: The growth of grammar. Mit Press.
Luine, V. N. (2014). Estradiol and cognitive function: past, present and future. Hormones and
behavior, 66(4), 602-618.
Mehrgan, K. (2014). Critical Period Hypothesis: A Perspective from Second Language
Acquisition. United States of America Research Journal, 3(4).

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Ren, J. (2017). Reflecting on the Primary Phonetic Learning Based on the Critical Period
Hypothesis in Language Acquisition. Theory and Practice in Language Studies, 7(10),
900.
Rund, B. R. (2014). Does active psychosis cause neurobiological pathology? A critical review of
the neurotoxicity hypothesis. Psychological medicine, 44(8), 1577-1590.
Saxton, M. (2017). Child language: Acquisition and development. Sage.
Temprana, S. G., Mongiat, L. A., Yang, S. M., Trinchero, M. F., Alvarez, D. D., Kropff, E., ... &
Schinder, A. F. (2015). Delayed coupling to feedback inhibition during a critical period
for the integration of adult-born granule cells. Neuron, 85(1), 116-130.
Veríssimo, J., Heyer, V., Jacob, G., & Clahsen, H. (2017). Selective effects of age of acquisition
on morphological priming: Evidence for a sensitive period. Language Acquisition, 1-12.