Critical Period Hypothesis of Language Learning

My father, while he was in his early twenties immigrated to the States from India along with his parents, 4 older siblings and 1 younger sibling. Although they had all learned English in school, they never spoke in English as the need had never occurred. Their reading and writing proficiencies were possibly at an advanced level but their speaking proficiency did not reflect the same. It has now been 30 years since the move. My father, along with all my uncles and aunts, are fluent speakers of English, however, in terms of accuracy, they are not as perfect as native speakers. According to the critical period hypothesis, there is a biological timetable within which language acquisition must take place. If not, although language can still be acquired, it is near impossible to match native-like standards.

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The critical period hypothesis (CPH) though initially postulated by Penfield and Roberts, was popularized by Lenneberg in 1967, who connected the hypothesis to primary language acquisition and specified the importance of its occurrence before puberty. Birdsong (1999) explains the concept in the following manner, “because of progressive lateralization of cerebral functions and ongoing myelination in Broca’s area and throughout the cortex, the neural substrate required for language learning is not fully available after the closure of the critical period” (p.3). Other researchers began to consider the application of CPH in second language acquisition. Snow and Hoefnagel-Hohle (1978) talk about a similarity in the pattern in which both first and second language acquisition take place especially in terms of rules and structures (Dulay & Burt 1974; Fathman 1975), learning strategies (Cook 1973; Ervin-Tripp 1974) and errors (Taylor 1975).

Support: Birdsong (1999) in his book on CPH included the work of Eubank and Gregg who talk about the neural mechanism behind a critical period. It is a period during which the plasticity of the brain, i.e. ‘the ability of neurons to make new connections’ (p.69) is at its best (although a particular age range was not specified). They describe two processes that are responsible for this plasticity called long-term potentiation (LTP) and long-term depression (LTD). It must be mentioned that the authors were careful to admit that there is information that needs to be added to what has already been established. It has been observed that in LTP, receptor molecules once activated, release calcium which ‘increases synaptic efficiency’ (p. 69). It is suggested that if this mechanism is not exposed to external stimuli during the critical period, it could lead to the inhibition of new neural connections, which in turn retards language acquisition.

Assuming the relevance of Chomsky’s universal grammar (UG), which is an innate system of inherent universal grammar rules that enable normal speakers to acquire their first language, Birdsong (1999) says that its withdrawal after puberty is another reason why language learning might be difficult or slow after puberty. He goes on to talk about the ‘language learning faculty’ which gradually deteriorates due to the extravagance of its existence (loss of energy) or the lack of it being used (muscle atrophy), once the first language has been acquired. Wasserman (2007) mentions that second language is best acquired at the age of ten as it is a time when the plasticity of the brain is highly active and “the brain is already wired for language acquisition” (p.2).

Against: In a research conducted by Snow andHoefnagel-Hohle (1978), English speakers of different age ranges were tested on their pronunciation, auditory discrimination, morphology, sentence repetition, sentence translation, sentence judgement, story comprehension and storytelling skills in Dutch. Overall, they noticed that participants through the ages of 12-15 and adults made ‘fast progress’ in learning the language while participants through the ages of 8-10 and 12-15 had the ‘best control’ over the language by the end. They then concluded that their results did not prove to be in favor of a critical period hypothesis as adults were able to learn the language just as fast as teenagers. In another research conducted by Bialystok (1997), it was noticed that the age of language acquisition was not as influential as the duration in which time was spent using the language, to achieve native-like fluency.

Critique: There have been considerable amounts of research regarding the validity of the critical period hypothesis, especially pertaining to the definition and duration of the critical period. Many of the researchers do agree to the existence of a critical period, however the exact time or age of its occurrence is still a topic under discussion. There is also a need for specificity in terms of a universal definition of a second language.

In India, bilingualism is a common trait that is seen throughout the country. In the rural parts of Bangalore, a city in the Southern state of Karnataka, villagers speak the state language, Kannada, along with Telugu which is the state language of Andhra Pradesh (another southern state of India), both of which are Dravidian languages. Children in the villages of Bangalore, grow up being exposed to both Kannada and Telugu, right from the time of their birth. However, when asked about their second language, students and teachers from government schools refer to English rather than Kannada or Telugu (whichever was acquired first). This is due to the educational system in the government schools in Karnataka where Kannada is the first language, English is the second language and Hindi is the third language.

Additionally, more research should go into explaining the extent to which a language must be acquired before puberty, along with the skills and quantifiable levels at which learners must be to ascertain their fluency in a language after puberty. Based on a brief survey taken by 15 participants from both rural and urban parts of Bangalore between the age range of 13-54, the languages they have learned fall under two categories:

Languages that are implicitly acquired according to Krashen’s definition of acquisition i.e. without the formal and systematic study of the language. 

Languages that are explicitly studied through formal education right from primary through high school.

It was observed that the languages acquired under the first category occurred before the age of 5 (mainly Kannada and Telugu, in this case). Languages explicitly learned, English in this case, began at the age of 5. However, in terms of spoken proficiency, the participants seemed more fluent in the languages that fall under the first category.

Another key factor that played a role in determining fluency in a second language is the level of immersion. Almost all of the participants had acquired, learned or was learning their second language before the age of 12. It was observed that those of them who studied in their second language and were immersed in the same language in their school environment, fared much better in all four skills- reading, writing, speaking and listening- than those of them who learned in a non-immersive environment. Thus, more information regarding what it means to acquire a language and how it should be acquired within the context of a critical period, requires more study and analysis.

Lateralization

Lateralization of the brain is a fascinating concept that deals with handedness, language, reasoning, creativity and social skills and emotions. Researchers have varying views regarding the relevance of the right or left hemisphere in the process of language processing or language acquisition. The popular notion is that the left hemisphere deals with language processing, especially due to the presence of the Wernicke’s area and the Broca’s area in the left hemisphere. The Wernicke’s region is located in a section where the parietal and temporal lobes meet and is responsible for the comprehension of speech while the Broca’s area is responsible for the mechanism involved in the production of speech and is present in the frontal lobe. Although the association of language and the left hemisphere is quite popular, there is much speculation as to whether it can be declared as a universal trait. There are studies which show that in an informal setting the right hemisphere is used more in language learning than the left. Some say that in an informal setting, adults use the right hemisphere in language learning (Brown, p. 56, 2014). 

Research has shown a strong correlation between handedness and language, which further questions the absolute nature of the dominance of the left hemisphere in language processing. In a research published by Knecht et. al in 2000, 326 healthy men and women between the ages of 15-49 were tested to see if there is a correlation between handedness and hemispheric language dominance. They found a linear correlation in the dominance of language processing in the right-hemisphere with an increase in left-handedness.

Szaflarski, Holland, Schmithorst and Byars (2006) in their research tried to establish a relationship between age and language lateralization. According to their findings, language lateralization occurs more in the dominant hemisphere from the ages of 5 through 20, plateaus between 20 and 25, and decreases between 25 and 70. All of the participants of this research were healthy right-handed adults and children. Hence, they found that the language dominance was oriented strongly in the left-hemisphere in children and adolescents, and was at its strongest at ages 20 through 25.

From these findings, it may be safe to assume that adults (>25) use their right hemisphere for language processing more when compared to children and young adults where the left hemisphere is used. Theoretically, this could mean that adults would prefer creative and interactive ways to learn a language as compared to children and adolescents who might be more sensitive/prone to deduction by immersion. According to Wasserman (2007), although the language center is located in the left hemisphere, children use their right hemisphere for all learning up until the age of 5. Thus, after this period, a whole-brain teaching approach should be followed in classrooms to appeal to students who are at different developmental stages and have different styles of learning, by utilizing a variety of interactive, reflective and analytical methods to create an optimum learning environment.

Again, taking the example of the kind of education that takes place in the rural parts of Bangalore, although the walls of an elementary classroom are visually stimulating with charts of information from all the different content areas, the general approach to teaching seems to be geared towards left-brained learners. Students begin to learn English in a linear fashion, starting with the alphabets, followed by basic grammar rules and then on to more content-heavy lessons. The two most common techniques of teaching are repetition and copy-writing. Teachers believe that by having students repeat the alphabets or the lessons and by making them copy passages from their textbooks into their notebooks, students will implicitly learn how to read and write in English. Although this approach has its benefits it would be more productive in the long run if it were combined with more creative ways of learning so that it appeals to both kinds of learners.

The process of cognitive development and language acquisition

According to a graph included in a research conducted by Sakai (2005), children progress from babbling to sentence formations from the time of their birth to the age of three. Stackhouse and Wells (n.d.) in their book called Children’s Speech and Literacy Difficulties, spell out three phases in which speech emergence can be tracked in young children- Prelexical phase, Whole word phase and Systematic simplification phase. The prelexical phase is observed in neonates all the way up to 9 months. It is a time when babies respond to speech, begin to babble and progress into monosyllabic sounds and high-pitched noises to express emotions. An interesting point to note according to Stackhouse and Wells is that “[neonates] are better than adults at discriminating between pairs of speech sounds which are either not present or are not linguistically significant in the language to which they are exposed” (p. 190).

The whole word phase occurs around the time of 12 months where words begin to emerge. They go on to describe it as a phase where “semantic representation, phonological representation and motor program, [are] all linked” (p. 197). Hence, by now, although emergence and comprehension of speech are still developing, the foundations of speech processing have been established. In the systematic simplification phase, it is predominantly phonological development that takes place.

Although it is not ideal to compare first language acquisition in children with second language acquisition in adults, according to Krashen and Terrel’s Natural Approach, language must be acquired rather than learned by adults, thereby mimicking the process of language acquisition in children. This would account for the silent period Brown (2014) critiques this approach by saying, “Because learners did not need to say anything until they felt ready to do so, and because the teacher was the (sole) source of the learner’s input, the method bore only mild resemblance to child language acquisition- first or second” (p. 74).

For adults learning a second language, 

The importance of children being exposed to language at an early age

Things related to brain development that support critical period Hypothesis:

Consider conclusion of Wasserman article for conclusion

Savitha’s quote in conclusion- goal is passing not learning to use language.

References

Szaflarski_et_al-2006-Human_Brain_Mapping.pdf,” n.d.)

(z)Bialystok, E. (1997). The structure of age: in search of barriers to second language acquisition. Second Language Research, 13(2), 116–137. https://doi.org/10.1191/026765897677670241

(z)Sakai, K. L. (2005). Language Acquisition and Brain Development. Science, 310(5749), 815. https://doi.org/10.1126/science.1113530

(z) Stackhouse, J. and Wells, B. Children’s Speech and Literacy Difficulties : A Psycholinguistic Framework. (n.d.). Retrieved December 3, 2018, from https://web-b-ebscohost-com.ezproxy.wheaton.edu/ehost/ebookviewer/ebook/bmxlYmtfXzEzMjAxX19BTg2?sid=90a3ac9c-14e2-41cb-afb6-070c0b322ebe@sessionmgr101&vid=13&format=EB&lpid=lp_220&rid=10

Snow & Hoefnagel-Hohle, (1978)

(z)Wasserman, L. H. (2007). The Correlation between Brain Development, Language Acquisition, and Cognition. Early Childhood Education Journal, 34(6), 415–418.

Brown, H. (2014). Principles of language learning and teaching: A course in second language acquisition (Sixth ed., Always learning). White Plains, NY: Pearson Education.