Age Effects on Second Language Acquisition

1. Introduction

There has been a consensus in linguistic field that effects of age can be crucial in both first and second language acquisition. The popular belief that adults have to work hard at second language learning and are likely to be less successful at achieving native-like level of competence when compared with the younger, has been supported by some professional literature, e.g. Lenneberg (1967), thus contributes to the proposal of the Critical Period Hypothesis (CPH), which refers to the hypothesis that there may be an optimal age period for language acquisition, and only the language learning occurring before the onset of puberty can lead to full language cognition (Penfield & Roberts, 1959, Lenneberg, 1967). As the critical period in L1 acquisition has been supported by the evidence in previous studies, e.g. the studies on Genie (Rymer, 1993) and feral children (Candland, 1993), the question whether there is a critical period in L2 field, and how age differences effect L2 acquisition wou­­ld be worth further exploration.

Therefore, the following paper shall explore age effects in second language learning. It shall intend to explain the relationship between age of exposure and second language acquisition from the aspects of phonology, morphosyntax, learning rate and other motivational factors in language learning. Related research literature would be provided with specific cases on the basis of the author’s own language learning experience. Finally, the summary of this paper and suggestions for further study shall be presented.

2. Literature Review

According to CPH, there is a specific period of time in human’s early life when the brain shows a special propensity to attend to certain experiences in the environment and learn from them, which ends at about puberty (Ortega, 2013). It means the brain is pre-programmed to be shaped by the input in surroundings, within a biologically specified time period. In this case, it is reasonable to suggest the critical period also works in the second language acquisition, which is supported by the observations that children tend to be adept at learning other foreign languages as well rather than only their first language (Penfield & Roberts, 1959, Lenneberg, 1967). In addition, according to Scovel (1988), there are maturational changes in brain structures that are used to process language. It has been hypothesized that after the brain’s maturation, it loses neural plasticity for language learning, which can be seen as evidence for CPH in second language field.

There have been a variety of studies investigating the age constraints on L2 acquisition with the reference of CPH. For confirming the existence of critical period, there is an expectation for the results of these studies: there should be a correlation between the age of beginning L2 learning and L2 performance within a specific age period (before the puberty), and no correlation for the ages beyond it (Flege et al, 1999). In this section, the related research literature about CPH and corresponding age effects in L2 acquisition would be discussed from different aspects, in which the author’s personal experience would be involved.   

2.1 Age and Second Language Morphosyntax

The evidence for age effects on L2 morphosyntax can be found in cognitive neuroscience. Some researchers have found the localization of language functions in the brain of late L2 starters is less lateralized than the one of early starters and native speakers (Ortega, 2013). E.g. Helen Neville and her lab have found evidence that the bilingual brains of late starters (8 years or older) show clear different activation patterns from those of monolinguals and early starters (cited in Ortega, 2013). Besides, according to Ullman (2001), the learning of syntactic functions is found to be fundamentally different from the learning of semantic features. More specifically, the syntax processing involves computational learning mechanisms and will be constrained by a biological schedule, whereas the semantics processing is free from critical period constraints. All these converging findings tend to support a critical period for L2 morphosyntax.

However, although many studies have been taken for a long-term view on ultimate attainment and evaluation of the end state of L2 acquisition, the research results present a consistent dissonance. In the study by Johnson and Newport (1989), the focus is on ultimate attainment of the L2 grammar as a function of the age when learners are exposed to target language, it tests subjects’ knowledge of numerous aspects of English morphology and syntax. The result presents that, from the perspective of ‘age of exposure and ultimate command’, there is a relation between age of acquisition and ultimate performance in the L2 grammar, and children have an advantage over adults in acquiring L2 morphosyntax, which is in accord with the results of the previous studies by Oyama (1978) and Patkowski (1980): there is a linear trend between the age of exposure and the performance in L2 grammar. Nevertheless, from the perspective of the comparison between effects of age before and after puberty, the finding is much more controversial: Johnson and Newport (1989) suggest the relationship between age and performance disappears after puberty, which can be seen as evidence for the existence of critical period in L2 acquisition (DeKeyser, 2000).

Although in DeKeyser’s study (2000) the findings resonate with those of Johnson and Newport (1989), in the study by Birdsong and Molis (2001), the grammaticality scores keep gradually declining across the ages beyond puberty, as well as in Oyama (1978) and Patkowski (1980). Moreover, Flege et al. (1999) found the participants’ knowledge of English morphosyntax did not decrease as the result of the increasing ages of exposure and suggest that the knowledge of ungeneralizable aspects of L2 morphosyntax improves gradually as a function of experience using the L2. They also argue that the age effects on morphosyntax are more likely to be caused by variations in education and language use rather than a maturationally defined critical period. If the conclusion is correct, there may be no sensitive period for L2 morphosyntax acquisition.

To sum up, as Ortega (2013) maintains, the doubts whether there exists a critical period for L2 grammar learning will keep going on as long as studies presented to exhibit there is no sharp drop in ultimate command of grammatical knowledge after the suggested age period. Nevertheless, based on personal experience and opinion, the age effects on morphosyntax does exist and individual performance of L2 grammar tends to decrease as the one’s age of exposure of L2 increases, which mainly results from various levels of language use and practice correlated with age (Flege et al., 1999). For instance, I started to learn English grammatical morphosyntax since 11, and as a result of corresponding policies in different provinces (Hu, 2008), some of my peers began to learn grammar at an earlier age like 8 or 9. It turns out they were likely to gain higher scores in grammaticality judgement tasks in various exams and showed a more complete ultimate command of L2 morphosyntax. However, as I majored in English in undergraduate study and had to use English more frequently whereas some of them who started to learn grammar earlier but used English relatively seldom in university, I obtained higher lexically based scores in CET (College English Test-Spoken English Test), which keeps in accordance with the finding in Flege et al. (1999). Therefore, I believe that there are age effects on morphosyntax acquisition, but it is less independent to non-biological factors.

2.2 Age effects on L2 Phonology acquisition

The acquisition of L2 phonology is believed to be influenced by the age issues to a great extent. As Scovel (1998) maintains, the speech has a special status in the critical period because ‘pronunciation is the only part of language which is directly “physical” and which demands neuromuscular programming’ (p.62, cited in Ortega, 2013). There are two assumptions for explaining the age effects on L2 phonology: on the one hand, as mentioned in previous section, it has been assumed that the brain becomes less ‘plastic’ to learn another language after the maturation (Scovel, 1988). On the other hand, L1 system is believed to influence the processing of L2 learning. It hypothesized that, all else being equal, when L2 learning starts, the more fully developed the L1 system is, the more strongly the L1 will influence L2 (Flege et al, 1999). In this case, the CPH is held to be relevant for the L2 pronunciation learning, and there is a common agreement that some special facility for phonological acquisition may disappear at puberty (Braine, 1971).

For proving that the native-like pronunciation ability may be influenced as the age of exposure increases, the evidence accumulated since 1988 has strongly shown that foreign-sounding accents are likely to develop when L2 is learned later in life (Ortega, 2013). The similar point can be found in Snow and Hoefnagel-Hohle (1977), they suggest that the correct articulation of the sounds in a L2 is believed to be the most difficult aspect to acquire after the critical period (ages 3-15, in their study), which is supported by many cases of adults who are able to speak fluently and grammatically correctly, but still maintain a strong foreign accent. In addition, in Flege et al. (1999), Koreans who learn English after puberty are likely to have difficulty in accurately producing and perceiving certain English vowels. Nevertheless, while the older starters have problems in phonetic skills of L2 which can be eliminated only through special training (Christophersen, 1973, cited in Snow & Hoefnagel-Hohle, 1977), children can lose foreign accents automatically.

All these facts suggest there exists the relationship between the age of beginning L2 learning and the L2 phonology thus call for further exploration in these issues. In the study by Snow & Hoefnagel-Hohle (1977), it suggested the ages 3-15 contribute to an optimal period for ultimately achieving near-native foreign pronunciation, which cannot be explained in terms of any neurologically determined critical period, whereas Flege et al. (1999) emphasize psychperceptual and phonetic causes related to previous experience with the mother tongue, rather than explaining L2 phonology learning from the aspects of neurophysiological maturational constraints (cited from Ortega, 2013). More specifically, in the study by Flege et al. (1999), the native Korean participants’ strength of foreign accent in speaking English grew stronger as their age of arrival in the United stated increased. The later arriving group had significantly stronger foreign accents than the earlier arriving group did, with the other variables controlled. The result shows a child advantage for phonology learning, which keeps in accordance with previous studies by Snow & Hoefnagel-Hohle (1977) and Olson & Samuels (1973).

Therefore, it is fair to suggest a sensitive period in L2 phonology learning (Flege et al.,1999), which may arise from brain maturation, maintained by Oyama (1973,1979) and Bornstein (1989), or according to Flege and his colleges, more likely from changes in how the L1 and L2 phonological system interact as the L1 system develops. In this sensitive period, Flege and his colleagues believe that, as the mental representations of speech sounds in L2 are stabilized by age 5-7, the learning of new phonetic categories can be more difficult and influenced by L1, which results in the age effects on L2 phonology learning. Moreover, the two moderating variables in the study: amount of L2 use and amount of education for L2 are found to be more related to the morphosyntax learning, as mentioned in previous section, which suggests that, compared with morphosyntax acquisition, phonology may be more independent to non-biological factors, and more closely related to biological schedules.

Based on my individual L2 learning experience, the L2 phonology is likely to be strongly influenced by the age of exposure and less related to non-biological factors like the amount of L2 input or education for L2. For example, I started to learn speaking English in language institutions at the age of 5, while most my peers started to learn English phonology at the age of 7 or 8 in schools. Although I still have foreign accent as there is a lack of enough exposure of English input in my childhood, I have less difficulty in accurately producing and perceiving English vowels and consonants, whereas these late starters may learn new phonetic categories in English more difficultly where the L2 learning may be influenced by L1, e.g. pronouncing [ a: ] as [ Λ ], or [æ] as [ai] (Hu, 2009), which is caused by the interaction of L1 phonology system. In addition, as for the accent issue, I found myself a distinguished accent even after over 10 years language use and one-year overseas experience in the United Kingdom, whereas my 6-year-old nephew, who immigrated to United States at the age of 2, has a native-like accent. Therefore, it is sure for me that foreign accents get stronger as the age of exposure increased and are more impervious to non-biological factors.

2.3 Age and Learning rate in L2 acquisition

There is a common misunderstanding in second language acquisition: children learn faster than adults (Ortega, 2013). Despite of the fact that children who were exposed to the L2 can get ultimate attainment of target language while adults may not, children are not likely to learn a L2 faster than adults. On the contrary, the research has shown that immigrant children’s L2 learning is slower than adults’, but they keep going until they get the native-like level of language competence whereas adults show some form of limited development (DeKeyser, 2013). More studies on the learning rate of children and adults have been made since 1970s.

Through various studies, SLA researchers have found an advantage for adult L2 learners over children in short-term tasks, and young learners is better in the long run. E.g. in the study by Snow & Hoefnagel-Hohle (1977), adults and adolescents were found to be better than children in terms of what they could learn in a 35-minute instruction session and the up to a year of exposure to the L2 Dutch (cited in Ortega, 2013). More specifically, in this study, the order shows an advantage of pronunciation over children, but the younger learners begin to excel after only one year. In other words, the younger subjects who were worse at the beginning, are likely to continue their period of active acquisition longer, and eventually catch up the order subjects who kelp at a relatively lower point (Snow & Hoefnagel-Hohle ,1977). The similar result can be found in Long (1990) and Patkowski (1980), where the order is better initially and able to learn faster at the beginning, but the rate advantage for the order learners dissipates after a little more than a year. The reason for that, according to Krashen et al. (1979), may be that the short-term instruction or tests demanded cognitive maturity and metalinguistic skills, which are easier for adults.

However, the various degrees of the intensity and quality of exposure to the L2 can lead in radically different results. In the study by Munoz (2006), where L2 is only available through instruction, after the comparison between early starters from ages 8-16 and late starters from ages 11-17, it suggests that the late starters actually maintained an advantage over young starters that persisted after 5-year instruction. Therefore, as Singleton (2003) suggests, in a learning context, the universal age effects nay be moderated and thus need to be considered carefully. Generally speaking, in foreign language contexts, young starters can capture any lasting differences between them and the older starters within five years (cited in Ortega, 2013).

On the basis of my personal experience, it is true that adult learners have a rate advantage over children in short-term institution tasks. When I was 5 years old, my mother, who had few English knowledge before, attended the six-month language institution with me, and acquired the taught contents faster than me so as to help with my homework. Besides, she learned the phonology of English faster and better, which allowed her to correct my pronunciation sometimes.

2.4 Age Effects on Motivation and Affective factors

The adult-child differences in L2 acquisition might also be due to differences in how learners regard the second language or the need to modify previously established patterns of pronunciation (Flege, 1987). For children, according to Snow & Hoefnagel-Hohle, the longer period of acquisition may result from their greater motivation to achieve native-like skills, or from their greater need to produce correct pronunciation to communicate with peers. Macnamara (1973) also suggests that children may face greater social pressure than adults to pronounce L2 authentically because they feel a greater need to participate fully in the culture associated with L2, which pushes them to have native-like accent, whereas adults have instrumental motivation which refers to the wishing to get a salary bonus or get into college for practical reasons may be much better at other aspects of second language skills like vocabulary and morphology.

In addition, Schumann (1978) suggests that affective factors can be significant in determining success in L2 pronunciation. According to Guiora (1972), L2 pronunciation patterns may become a manifestation of personal identity once an individual has a sense of ‘language identity’, which leads the L2 learners regard the modification of previously established pattern as the threatening to his ‘language ego’ (citen in Flege, 1987). In this case, adult learners may be more motivated to fail in achieving perfect mastery of L2 due to the fear of losing their cultural-personal identities (Christophersen, 1972). These various motivational factors, combined with the age effects on other aspects in L2 acquisition, can provide additional explanation for the long-term superiority of younger learners.

3. Conclusions

In this paper, it discussed the age effects on second language acquisition from different aspects of morphosyntax, phonology, learning rate and other motivational factors in English learning. In summary, the young learners show an advantage over the order starters in second language learning. In L2 morphosyntax learning, the age effects come from non-biological aspects such as the amount of L2 and education for L2, whereas in phonology learning, the age effects on phonology may have been due to a sensitive period arising from brain maturation or the changes in how L1 and L2 phonetic systems interact. As most present studies focus on the foreign contexts with great exposure of L2, for further study on age effects in second language acquisition I would suggest a learning context of L2 where limited exposure is likely to be provided through instructions.

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