THE CRITICAL PERIOD HYPOTHESIS

THE CRITICAL PERIOD HYPOTHESIS

Second language acquisition (SLA) is affected by many different factors in its process of acquiring a foreign language. Some of them are considered common to every non-native speaker and they can affect in a different manner each individual. The element that will be analysed in this paper will be the age of onset (AO), a biological factor that is considered a strong predictor of success in SLA. According to Granena (2013), whilst L2 morphology and syntax is often proceeded faster by adolescents or adults through early stages, which is a rate advantage, the expected level of ultimate L2 attainment generally diminishes with the increase of AO. With regard to the age effects, there is less agreement between researchers: variation in the quantity or quality of input to younger and older learners, differences in their affective profiles or cognitive maturity are some of these effects discussed by experts.

One of the most known hypotheses that supporting this is the Critical Period Hypothesis (CPH). This theory is used with two different meanings explained by Pallier (2007). The first explanation is based on an empirical hypothesis denoting that humans are more efficient at language learning in the first years of life (it can also be applied to L1 acquisition). Moreover, it is an important predictor of ultimate proficiency, because the older an individual starts to learn a language the smaller the possibilities of reaching a native-like competence this person will have. The second argument stands on the conviction that an age-related decline in neural plasticity is the cause of increasing difficulties in language learning. These two meanings must be distinguished because, according to the first meaning, the reason for not achieving a native-like proficiency can be due to other causes different from irreversible neural plasticity changes, whilst the supporters of the second meaning believe that this loss of plasticity is because of maturational factors.

However, other researchers suggested that it could also be due to the outcome of language acquisition itself. Penfield (1965) advocated that before the child begins to speak, the cortex is blank and nothing is written on it. Over time, this begins to be written and normally not erased. For the author, at the age of ten or twelve connections produced within the cortex have now been established and fixed in the speech of the individual. An alternative theory supported by Pinker (1994) asserted that once the circuitry of language acquisition has been used, it should be removed if it becomes an issue for keeping it. All neural tissue used beyond its point of usefulness is a good starting point for being recycled.  Therefore, both theories had a point in common: once the young learner has acquired the language or languages around him or her, the neural modifications are impossible to reverse.

Pallier (2007) asserts that there have been many studies carried out for the CPH. Some of these studies were performed with animals that required depriving them from some relevant stimulus during a period of time. On the other side, experimentation with humans for the L1 acquisition has not been accomplished for understandable reasons, as it would not be ethical, because it would signify the denial of language exposure for children. Notwithstanding, some studies have been performed with abandoned children who had little language exposure at first, and observations suggested that their language skills were limited even after language instruction. Other human studies performed in this area have been accomplished with groups of deaf people who learned sign language as an L1 at different ages. The results showed that those people who were exposed to sign language in their first years of life had a better control of the language than those later exposed. Eventually, those who later started (in mid-childhood) performed better than those who were exposed first when they were ten or more.

Although it could be asserted that critical neural changes take place during the puberty period, it seems that it can occur much earlier. Studies conducted with deaf children who received cochlear implants (an auditory technological device surgically implanted to stimulate the auditory nerve in order to transmit acoustic information to the central auditory system) displayed that there are beneficial effect of earlier implementation in children when they are already 1 to 3 years old (McConkey Robbins, Burton Koch, Osberger, Zimmerman-Philips & Kishon-Rabin, 2004).

Another domain for collecting data connected to the CPH is SLA. As stated by Snow (1978), there are two types of research designs that can be expected from this sort of research. The first one is by comparing second language acquisition to first language acquisition. The second one involves comparing SLA across a wide age range. Diverse studies have shown that second language acquisition is similar to first language acquisition, with regard to the order in which rules and structures are acquired (Dulay & Burt, 1974), of the learning strategies employed (Cook, 1973) and of the errors made (Taylor, 1975).

Moreover, other studies contemplated by Ervin-Tripp (1974) and Fathman (1975) that used the second strategy displayed that older children (even adults) proceeded faster L2 morphology and syntax. There were even other studies accomplished by Asher & Price (1967) showed a faster listening comprehension by older children. However, rather than showing an agreement in the obtained results, they revealed wide discrepancies in some aspects. For instance, in pronunciation, there were some studies that displayed a better pronunciation in older subjects, whereas others showed a negative effect of age. There were even other studies in which there were found cases where there were older learners without accent in their L2, as well as cases who maintained their native accent.

Although the studies observed so far do not endorse the predictions established by the CPH, for Snow (1978) this hypothesis cannot still be rejected due to the problems that will be explained. The first issue that these studies contained was that they have only looked to a restricted age range. For example, in Fathman’s study the ages were between 6 and 15, in the case of Ervin-Tripp the ages were from 4 to 9, and with respect to the case of Asher and Prise, they only took 8 adults. The second problem they presented was that age differences were not assessed longitudinally, since all the age differences found were given at a random point after the beginning of SLA, rather than having constant differences in the rate of acquisition. Therefore, the only type of study that can provide a general idea of the age differences in rate acquisition or in ultimate achievement is a longitudinal one. In addition to this, a fairly limited range of second language abilities were tested in most studies and the CPH seeks to test different language abilities separately, since the acquisition of each ability may affect differently on brain plasticity. By doing this, contradictory findings could be explained and results would be more accurate.

Another sort of studies concerning the CPH in SLA have been those who have investigated the possible effects of age at immigration. According to Stevens (2006), these researches were made due to the high interest in the possibility of finding critical periods in language learning.  However, the process of learning a language takes some time, thus scholars had to take into consideration the effect of immigrants’ length of residence in the destination country with the purpose of isolating the effects of age at onset of L2 learning. For doing these kinds of studies, researchers took into account three variables, “age at immigration”, “length of residence”, and “age at testing”. Nevertheless, these three variables are linearly interconnected, so investigators had to ignore one or two variables in their respective studies in order to solve this problem.

The results provided by these researches showed for instance that length of residence in the host country hugely affected immigrants’ levels of proficiency in their L2 (at least in the first several years after their arrival to the receiving country). According to researchers, this was due to the fact that there were processes related to senescence and life-cycle stages. Immigrants’ ages at the time observations also took an important role in their investigations. Nonetheless, as they expected before doing researches, the three variables were impossible to consider simultaneously, and unfortunately, there are no easy statistical techniques that can disentangle the linear dependency among them. Chronological age was the variable that was most often omitted in the analysis, because of its difficulty for being followed (Stevens, 2006).

To sum up, it can be asserted that the age of onset has an important role to play in SLA. Moreover, it has also been observed that for learning a language the younger is usually the better. Although research will be better performed in the future, thanks to technology improvements and the correction of previous research errors, in this moment, it cannot be stated the exact age where individuals will not be able to learn a language or acquire a high proficiency language level, but instead of this, we could assert that there is a sensitive period for learning a second language around puberty, which will not be the same afterwards.

REFERENCES

Asher, J., & Price, B. (1967) The learning strategy of the total physical response: some age differences. Child Development, 1219-1227.

Cook, V. J. (1973) The comparison of language development in native children and foreign adults. International Review of Applied Linguistics, 13-28.

Dulay, H., & Burt, M. (1974) Natural sequences in child second language acquisition. Working Papers in Bilingualism, 71-98.

Ervin-Tripp, S. (1974) Is second language learning like the first? TESOL Quarterly, 111-127.

Fathman, A. (1975) The relationship between age and second language productive ability. Language Learning, 245-253.

Granena, G., & Long, M. (2013) Age of onset, length of residence, language aptitude, and ultimate L2 attainment in three linguistic domains. Second Language Research, 29(3), 311-343. Retrieved from http://www.jstor.org/stable/43103927.

McConkey Robbins, 4., Burton Koch, D., Osberger, M. J., Zimmerman-Philips, S. & Kishon-Rabin, L.(2004). "Effect of age at cochlear implantation on auditory skill development in infants and toddler”. Archives of Otolaryngology Head & Neck Surgery, 130, 570-574.

Pallier, C. (2007) Critical periods in language acquisition and language attrition. In Language Attrition: Theoretical Perspectives, 155–168.

Penfield, W. (1965) “Conditioning the uncommitted cortex for Language learning”. Brain, 88,787-798.

Pinker, S. (1994). The Language Instinct. New York, NY: W. Morrow and Co.

Snow, C., & Hoefnagel-Höhle, M. (1978) The Critical Period for Language Acquisition: Evidence from Second Language Learning. Child Development, 1114-1128. Retrieved from: http://dx.doi.org/10.2307/1128751.

Stevens, Gillian. (2006) The Age‐Length‐Onset Problem in Research on Second Language Acquisition Among Immigrants. Language Learning, 671 - 692. Retrieved from: https://doi.org/10.1111/j.1467-9922.2006.00392.x.

Taylor, B. P. (1975). The use of overgeneralisation and transfer learning strategies by elementary and intermediate students of ESL. Language Learning, 73-107.