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Critical Period Hypothesis

After the critical period, most individuals face difficulties in learning a language. Using Lenneberg’s Critical Period Hypothesis and other psycholinguistic evidence, discuss this phenomena.




Topic 2: After the critical period, most individuals face difficulties in learning a language. Using Lenneberg¶s Critical Period Hypothesis and other psycholinguistic evidence, discuss this phenomena. Introduction Throughout the years, psycholinguists and linguists alike have tried to come up with explanations that account for how humans are able to acquire and learn language(s). Sadly, no one was able to come to an agreement on the exact science behind human language acquisition. What they do agree however, is that language acquisition and language learning are two entirely different things. Language acquisition refers to an acquisition of language outside of a classroom (Brown, 2007). This usually refers to our mother tongue or our first language that we µpick up¶ as a young child in an informal environment. Language learning on the other hand, is the exact opposite of language acquisition. It refers to the µconscious¶ learning of a language in a classroom or a formal environment. This nor mally would be any subsequent language learnt after  the first language. One of the major breakthroughs in hypothesising the phenomena behind language learning and acquisition was made by Eric Heinz Lenneberg (1921-1975). Lenneberg was a linguist and neurologist who pioneered ideas on language acquisition and cognitive psychology. He was a staunch believer in the innateness movement. Born in Düsseldorf, Germany he left the country with his family in 1993 due to the rising of Nazi persecution (Eric lenneberg 1967, n.d). The family originally settled in Brazil but he soon went to United States and furthered his studies at the University of Chicago and Harvard University. He obtained his PhD in psychology and linguistics and taught at Harvard Medical School, the University of Michigan in Ann Arbor and Connell University as a professor of psychology and neu robiology. Among all of his researches, Lenneberg most famous study involved the well known Critical Period Hypothesis, which he popularised in his publication, Biological Foundations of  Language in 1967. In it, he hypothesised that: i) Language learning is a biologically constrained co nstrained learning; ii) Language is normally acquired dur ing a critical period (early in life and puberty) 1 iii) Outside this period, language will be acquired through a different learning process or with difficul d ifficulty. ty. Critical Period Hypothesis The Critical Period Hypothesis (CPH) was first proposed by neurologist Wilder Penfield and co-author Lamar Roberts in 1959 but was popularised by Lenneberg in 1967 with his  publication, Biological Foundations of Language (David, 2007). One of the major supporters of  CPH includes linguist, Noam Chomsky. CPH is based heavily on the assumption that language is  biologically based and the ability to learn a native language is developed within a fixed period, from birth to middle childhood (Fromkin, Rod man, & Hyams, 2007). The critical period here refers to a time frame during which some crucial experience will have its peak effect on development or learning which could result in a swift and easy process of  language acquisition attuned to the particular environment to which the organism has been exposed to. So, if an American child is exposed to Mandarin before his puberty, it is very likely that the child will be able to speak Mandarin like a native. However after this period, the acquisition of grammar would be difficult and for many, never fully achieved. Children who were deprived of language during this critical period have been known to show atypical patterns of brain lateralisation. Generally, all critical periods; human or animals, shares a slightly similar geometric feature (Boxtel, 2005). The critical periods will have an onset, a peak of heightened sensitivity, an offset and a terminus with a flattening after the terminus (refer to figure 2.1 in Appendix). What this means is that during the onset, the organism involved will have an acute sensitivity towards the environment or stimuli. When it reaches the peak, exposure to the stimuli or  environment will be very effective. This continues on until it reaches the terminus indicating the end of the critical period. The ³flattening´ relates to Lenneberg¶s belief that once the child hits   puberty the stimuli will no longer be effective because the critical period has ended. To tie it   back to the problem statement, when a child has reached puberty according to Lenneberg, the child will not be able to learn a language easily. While the topic of CPH for humans is widely debated, it has been proven that there is a concept of critical period for other species. Ducklings for example were found; much to the joy of Konrad Lorenz (Lorenz, 1973), to imprint on and follow the first moving object they see, 2 whether or not it looks or waddles like a duck during the period from nine to twenty-one hours after hatching (Chakravarty, n.d.). Another species that is seen to have a critical period in learning a language is the white crowned sparrow. When brought up in isolation from a few days after birth, the birds would sing crude songs containing basic structures to the original white crowned sparrows¶ songs. However, if the birds were trained using a tape recorder within a specific time period (10-50 days after birth), they will eventually be able to sing the songs  properly. The birds that were exposed to the tape after the period will see little to no effect on the quality of the songs sung. The critical period seemed to relate to species-specific, biologically triggered behaviours (Fromkin, Rodman, & Hyams, 2007). The behaviour of the ducks and the sparrow were not the result of a conscious decision, external teaching or intensive practice but rather due to what appeared to be a maturationally maturationally determined schedule that t hat is universal across the species. Evidence for such a period to exist for humans are however, limited and support for this hypothesis comes largely from theoretical arguments and analogies but is nonetheless widely accepted. Be that as it may, Lenneberg seems to be of the mind that CPH does exist for humans and according to Boxtel (2005), Penfield and Roberts (1959) and Lenneberg (1967) based their  CPH on several pieces of evidence which were; i) Evidence from feral and abused children who had no exposure to human language in their childhood and were unable to acquire language normally after found ii) Evidence from deaf children whose development in spoken language stopped after   puberty. iii) Evidence that children with aphasia recovered better than adults with aphasia Brain Lateralisation According to Brown (2007), one of the most promising areas of inquiry in age and acquisition research is the study of the functions of the brain in the process of acquisition. Some   believe that brain lateralisation is the key to answering the question of language acquisition  because there is neurological evidence that as the brain matures; certain functions are assigned, or ³lateralised´, to the left hemisphere of the brain while other functions to the right hemisphere. Indeed, brain lateralisation is one of the ke y concepts used to support the CPH. 3 The foundation of CPH lies on the neurological research that suggests that after puberty, the brain functions will become lateralised (Moore, 1999). Intellectual, logical and analytical functions appeared to be mostly located in the left hemisphere while the functions pertaining to emotional and social needs are catered by the right hemisphere (See Appendix for list of  functions performed by both hemispheres). It is believed that the functions are not completely assigned to either portion of the brain before puberty. During the period before puberty reaches the child, the brain is considered extremely elastic (flexible). Following the line of thought for CPH, the prepubescent brain is like a ³sponge´ where all learning, knowledge and experiences will be µabsorbed¶. The µabsorption¶ of  language to nonspecific areas in the brain supposedly makes the learning of a language; first or  second, easier for the child compared to that of an adult or older adolescents. After the brain has  been lateralised, it is widely believed that language functions appeared to be mainly controlled in the left hemisphere although there is some contention pertaining to the location and functions of  the hemispheres. This is due largely to the fact that children with prenatal, perinatal, or childhood brain lesions in the right hemisphere has the possibility to show setbacks and impairments in babbling and vocabulary learning while children with early left hemisphere lesions demonstrate impairments in their capability to form phrases and sentences (Fromkin, Rodman, & Hyams, 2007). There are also cases where children who had a right hemispherectomy (surgery on the   brain¶s left hemisphere) could not develop language abilities despite having a left hemisphere. Be that as it may, many findings add up to show that, generally, the left hemisphere of the brain is essentially made for language while the right hemisphere is involved with a child¶s early language development. It has been found that children up to the age of puberty who suffered injuries to the left hemisphere were able to re-localise linguistic functions to the right hemisphere, to µrelearn¶ their  first language with with relatively little impairment under the right right circumstances. One such case was found in a longitudinal study of a boy who had no speech at 8 years of age after going through a left hemispherectomy but was able to recover his speech capabilities when he was 9 years old (Brown, 2007). Conversely, surgical removal of the left hemisphere in adults will indubitably result in severe loss of their language abilities. Of course it goes without saying that removal of  4 the right hemisphere will allow adults and children to retain their language abilities so long as they meet the right circumstances. c ircumstances. In order to answer the problem statement of this assignment, what is crucial here is actually not where the language functions are lateralised but when exactly the lateralisation takes  place and whether the t he process affects language acquisition. Lenneberg suggested that the slow process of lateralisation begins around the age of 2 and is completed around puberty (Brown, 2007). Take note that the age for the critical period varies in different accounts and, linguists and psychologists are unable to pinpoint an exact age for the critical period. During the critical period, the child is presumed to neurologically assign functions little by little to one side of the brain o r another. It was suggested that the plasticity of the brain prior to puberty is the reason why children are able to acquire their first language and any subsequent languages without any hindrances. It may be possible that because of lateralisation, adults are finding it harder to acquire a second language with the proficiency of a native speaker because they have lost their brain¶s elasticity. Second language learners who started after puberty were found to use more of their right hemisphere than the first language learners did. Obler (1981) and Genesee (1982) found that individuals, who acquire their second language late relative to their first language, used more of  their right brain. Brown and other researchers also observed more activity in the right hemisphere of the brain during the early stages of second language acquisition (Brown, 1994).   Now that the CPH has been explained in terms of brain lateralisation, the next section will explain other psychological theories that support it. 5 Support from Other Psychological Theories As mentioned before, Noam Chomsky is one of the notable proponents for CPH. Chomsky developed the innateness hypothesis , a linguistic theory of language acquisition where it is believed that language acquisition is innately determined. The hypothesis is supported  by an observation that the grammar a person ends up with is mostly not determined by linguistic experience because language acquisition is a creative process. This can be seen when children who are not given explicit information about the rules of a language are able to extract the rules from what they hear and make sentences based on the rules they gained (Fromkin, Rodman, & Hyams, 2007). It has been revealed through observations that children of different culture and social circumstances acquire language in a similar manner. That is why Chomsky stated that environmental factors are irrelevant to language emergence, because there are many factors surrounding the children while they are acquiring their first language. He used the existence of an innate knowledge to explain how a child is able to master a native language in such a short period of time even though the rules of language are highly abstract in nature. Chomsky and some linguists believed that humans are equipped with an innate template or blueprint for language known as the Universal Grammar (UG). UG is a collection of rules that represents the universal properties of all languages which allows it to provide a basic blueprint that all languages follow. In other words, UG provides the basic design for all human languages and individual languages like English, Mandarin, Tamil or any other languages are simply variations of the basic design. It specifies the different components of grammar and their  relations, how the different rules are constructed and so o n. For example, all languages no matter whether if they are eastern or western language, have phrasal structure rules where all phrase will contain complements and head but not all languages will have the same word order. An illustration of this would be where English Language has the word order of S-V-O (Subject followed by verb and object) but Japanese has the word order, S-O-V (Subject followed by o bject and then verb). These differences in language are called parameters. Chomsky believed that children will set the parameter at the correct value for their language thus allowing them to rapidly and easily 6 acquire a language. This is because the parameter of UG limits the grammatical options to a small defined set which helps to reduce r educe the acquisition burden on the child. UG is presumed to be contained in a µlanguage acquisition device¶ (LAD); a metaphorical ³little black box´ in the brain which restricts the possibilities for variations within a language while enabling learners to construct grammar rules out of µraw input¶ collected from the environment. Chomsky proposed that all humans were born with an LAD that begins functioning when they are still babies. The device enable humans to learn from their  environment so that by the time they reach the age of five or six, they would have a set of rules for their native language or first first language based on the universal grammar. UG was developed to explain first language acquisition but it can also be applied to second language learners who are able to achieve near-native fluency not solely on input and interaction. Those who learn during the ³critical period´ will be able to acquire language without any effort. However, our LAD will begin to function in different ways after we reach six years of  age. We remain able to acquire language fairly easily until we reach puberty, after which the ability to do so seemed to be reducing. Older learners must therefore learn languages in quite different ways from the effortless acquisition of young children. UG can also be applied to explain why adults will have difficulty d ifficulty in learning a language. As mentioned previously, children will set their UG¶s parameters according to the language used in their environment. Although it helps a child to easily acquire a language it will also affect the child¶s ability to learn a language after reaching puberty. The hypothesis is that   parameter setting is done early in development and cannot be undone (Fromkin, Rodman, & Hyams, 2007). What this mean is that once a person tries to learn a language after puberty, they will face difficulties because the parameters for that language was not set earlier on before puberty. For  example, an American child was able to acquire English easily when he was young because the  parameters were set for English language through the UG. Once the child grows up and tried to learn Japanese after the critical period, the child will face problems because the parameters for  English and Japanese are different and the child did not set the parameters for Japanese language  before puberty. Hence, it is clear that in this case, the CPH is again being supported. 7 Arguments from Biological and Cognitivist Theories The biological model is a school of thought that appears to come hand in hand with the CPH. This model is most prominently proposed by Eric Lenneberg (1967) as well as Penfield and Roberts (1959). In this model, the critical period of language acquisition is supported by Penfield and Roberts as being under the age of 9. Lenneberg, on the other hand, began by asserting that the critical period ended around the age of 4-5 (1964), before altering his view in later on. This change came about in part because of the focus on biological factor. Lenneberg (1967) concluded that if no language is learnt by puberty, it cannot be learned in a normal, functional sense, which is in agreement with the Problem Statement of this assignment. Puberty (which is around the age of thirteen but varies between individuals) is said to coincide with the   phenomenon of brain lateralization (already explained earlier), where the brain loses its  plasticity, becoming rigid and fixed ± with the left hemisphere fixed into language specialization. The drawback of this is that the brain ostensibly loses its ability for extensive adaptation and reorganization, rendering the learning of new languages much more difficult than before. Evidence: Intuitively, this appears to be accurate, but more proper evidence is seen from the cases of deaf and feral children. Firstly, ³feral children´ are rare cases of children who are not exposed to language during infancy or childhood due to being brought up in the wild, in isolation and/or  confinement. There are many scattered examples throughout recorded history, but two in  particular were studied and provided evidence e vidence for the Critical Period Hypothesis. The first is µGenie¶, who was deprived of social interaction by her mother until finally discovered and rescued at the age of thirteen. She was completely without language and still lacked linguistic competence even after 7 years of rehabilitation. She was able to acquire a significant vocabulary, but was unable to string them to form grammatical sentences. Another  case is µIsabelle¶, who was incarcerated with her deaf-mute mother until the age of six and a half. She also started out with no language skills, but quickly acquired normal language abilities through specialist training. Both children were similar in that they were deprived of normal linguistic input but responded differently to rehabilitation. Their defining difference was in their  8 age, as Genie was already thirteen while Isabelle was still pre-pubescent. This appears to support the hypothesis that language input is necessary during the Critical Period for it to be learned in a functional sense. Problems with the evidence? However, the evidence can be challenged on several grounds. Firstly, the isolation of  Genie could have produced general retardation and emotional trauma (unrelated to age) which affects her ability to learn language. There is a possibility that Genie was of sub-par intelligence due to her long period of isolation as well. Furthermore, the rehabilitation carried out for the two feral children were different. Perhaps a different methodolog y might have worked for Genie. However, Pinker (1994) supported Lenneberg¶s ideas by citing the example of a 31 year  old deaf woman known as µChelsea¶ who was unable to acquire language early in life because her deafness was only discovered much later. She was not abused mentally or physically as Genie was, but upon the belated discovery of her deafness and the fitting of hearing devices, her  language acquisition took on a similar, agrammatical pattern as Genie¶s (she was unable to grasp syntax). Obviously, the lady was well beyond be yond her supposed µCritical Period¶. Penfield and Roberts (1959) were also on the same track as they proposed that there are neurological mechanisms behind the maturational change in language learning abilities. This appears to explain why after a certain age (arbitrarily dubbed as the end of ³the Critical Period), language learning appears to be difficult, and absolute mastery of a new language and its  phonology in particular is extremely rare.  Nonetheless, these case studies are individuals; not a sufficient sample size for scientific study. Furthermore, it goes without saying that we have to rely on these exceptional cases for  study since it would be extremely unethical to purposely ³create´ conditions of language deprivation in people simply for research purpo ses. 9 American Sign Language ± Opposing Evidence? To circumvent these methodological problems, there are studies of deaf children learning American Sign Language (ASL) ± which is in itself a bona fide language. Newport and Supalla (1987) studied language acquisition in deaf children differing in age of exposure; few were exposed to ASL from birth, though t hough the majority learned it at school. schoo l. The results of this study challenged Lenneberg¶s CPH since it showed a linear rather than sudden drop in performance with increasing age of exposure. The late learners were exposed to ASL at age four (far before the CPH ends) and yet were shown to do poorer than the earliest learners. Hence, it is shown that language acquisition becomes harder as one becomes older, not suddenly when the critical period ends. Furthermore, Krashen (1975) had the benefit of  reanalysing clinical data ± showing that brain lateralisation happens much longer before puberty, contrary to Lenneberg¶s calculations. Hence, his biological basis for puberty being the end of the Critical Period is shown not to hold water. A linear rather than sudden drop in language acquisition in children is an idea that is in sync with the cognitivist view, most famously proposed and developed by the psychologist Jean Piaget (1926). Unlike the CPH, this view does not see language acquisition as distinct but simply another part of general learning and intelligence, which continues to develop even into adulthood. Intuitively, one is aware that even as an adult, journalists and writers continuously refine and improve their skills at using the language. According to Huitt and Hummel (2003), Piaget¶s work also revealed that only 35% of high school graduates reach the ³formal operational stage´ ± which is the highest level of intelligence. This shows that many adults appear not to think ³formally´, as opposed to the CPH which purports that one should have attained mastery of  a language by puberty. 10 Other possible explanations There are several other factors that can account for the difficulties an individual faces in learning a language besides being at an age over the critical period. One of these factors is simply the brain¶s aging. It cannot be argued that as a person ages, the brain¶s capacity to function as well as it used to be will decline. There will be certain age-related changes in a   person¶s cognitive processing with the increase in age. Recent researches have found that the effects caused from brain aging could be due to several reasons (Guttman, n.d.). These effects of   brain aging can range from age-related memory loss to severe conditions like Alzheimer¶s and dementia. On average, the brain loses 5-10 percent of its weight between the ages of 20 and 90. What this mean is that people of a higher age tends to forget things easier thus causing them to face more difficulties in learning something new compared to people of a lower age. Jeff  Victoroff, M.D., an associate professor of clinical neurology at the Keck School and director of  neurobehaviour at Rancho Los Amigos said that the reason our brains are declining with age may be because in the evolution 100, 000 years ago, it was considered rare for people to live past the age of  40 or 50 but because of technological advancement in medical research, this is no longer a problem. However, it also meant that there was little evolutionary selective pressure previously to make the human brain work when we¶re over  40. As a consequence, there will be a general decline in the brain¶s ability to process, remember and pay attention to things as an individual grows older. These declines in the brain¶s capability to function well will greatly affect the ease of a person¶s ability to learn a language. Aside from that, there are also learner-related factors that one should consider in the role of language learning. These factors are motivation, attitude and aptitude, and environment. There is evidence that shows that when a person is highly motivated to learn a language; the process will be smoother because the person is driven by the motivation to succeed in learning the language. The motivation can be an extrinsic motivation or an intrinsic motivation. Intrinsic motivation refers to a motivation guided by an internally rewarding effect like a sense of fulfilment, competence and so on while extrinsic motivations refers to reward from outside such as prizes, grades or other types of positive feedback (Brown, 2007). It is widely believed that intrinsic motivation has a stronger bearing than extrinsic motivation in the long run but 11 whatever the form of motivation may be, it can be safely said that should a person be motivated to do so, learning a language may not be seen as a difficult task for the person. The second learner-related factor is the attitude and aptitude of the person learning a language. Attitude is how the learner views the language he or she is learning. If the opinion that the learner has towards the language is positive then, no doubt the learner will be spurred on to invest time and effort into learning the language. Time, tutor, resources are some of the environmental factors that can affect a person¶s language learning process. An environment that is conducive will be able to optimise a person¶s ability for language learning. For example, if the tutor is unable to provide an effective teaching style that matches the person¶s leaning style the language learning process will become difficult even if the person is at an age within the critical period. The same applies to resources and time. If the resources are unsuitable and there is a time constraint, the person will be unable to learn a language easily. It could be, then, that adults find it so difficult to learn languages because most of our language teaching resources are tailored for and geared towards teaching younger students and not mature ones. 12 Conclusion To conclude, the Critical Period Hypothesis (CPH) by Lenneberg hypothesise that there is a crucial time frame for humans where experiences gained from the environment will have a  peak effect on development or learning which will result in a swift and easy process of acquiring a language. This is made possible because before puberty, a child¶s brain is still elastic and has not been lateralised. Once the brain has been lateralised the elasticity will decrease thus causing language acquisition to reach a flattening and learning a language during the period after puberty  becoming difficult. Recent research has shown that the flattening of the peak effect (sudden drop) does not happen but merely decline gradually as a person ages. This also proves that there is no welldefined age for the crtitical period. Despite the fact that the ability of a person to learn a language does not stop abruptly, age is still considered as a factor in language acquisition and learning. This is due to some age-related changes in a human¶s cognitive processing. Understandably, as human ages, the ability to recall details, encode new information and so on will become impaired and not as smooth as it used to be. These declines may account for the difficulty a person over  the critical age faces in learning a language. While Noam Chomsky¶s Innateness Hypothesis agrees with Lenneberg¶s CPH that there is a critical period in learning a language, there are several other linguists who do not think that CPH exist for human¶s ability to learn a language. In conclusion, CPH is still a matter of extensive debate. Both biological and cognitivist views support the idea of an innate source of language that activates upon exposure to the right kind of language input ± but their similarities end there. There is great debate when it comes to the manner, timing and limit of language acquisition, while the sparse evidence that is available are similarly debatable. 13 R eferences eferences d  Brown, H. D. (1994).  Pr inciples inciples of Language Lear ning ning and Teaching (3r d  ed.). ed.). Upper Saddle River, NJ: Prentice Ha Hall. ll. Brown, H.D. (2007). i nciples  P r inciples of language lea r ning n ing and teaching (5 th ed.).. ed.) Harlow, UK: Pearson Longman. Boxtel, S.J. (2005). Can the late bi r d catch the wo rm ? . Retrieved [3 April 2011] from 4 /bookpart.pdf  Chakravarty, I. (n.d.).  Does C r  i  tical  P er iod  iod  P lay lay a Role in Language Acquisition?. Retrieved ritical  [22 March 2011] from: in/users/hk/cs78 784/projects/indrani.pdf  David. (2007, December 17). 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