This essay addresses the question of whether the age at which a second language (L2) is acquired constitutes the only factor which accounts for oral proficiency accuracy in L2. The first part of the essay refers to the preponderance of age over other variables in language acquisition studies, and explains the most referenced theory: the Critical Period Hypothesis; providing evidence in favour and against it. The second section deals with other factors which may be involved on L2 production and perception variability. The relevance of this subject is not only determined by its value for language acquisition research, but also by the implications related to the educational perspective. It is a common view that speaking an L2 with a foreign accent is not a problem, unless it impedes communication, or in other words, speakers should aim at intelligibility, as “although strength of foreign accent is indeed correlated with comprehensibility and intelligibility, a strong foreign accent does not necessarily cause L2 speech to be low in comprehensibility or intelligibility” (Munro & Derwing, 1995: 74). This does not necessarily apply to particular learners, as it may be the case of foreign language teachers, newscasters, interpreters, singers, actors and actresses, who may be interested in acquiring a native-like accent.
Among the factors which account for proficiency in L2 acquisition, age has been considered the most important one, and therefore, it has been the most researched variable in experiments related to this area of knowledge. Lenneberg’s (1967) influential Critical Period Hypothesis (CPH) claims that there is a cut off period at puberty when acquiring an L2. After this critical period, complete mastery of the language is no longer possible, and for the oral competence in particular, learners will not be able to achieve a native-like accent. This theory is usually grounded on neurological changes such as loss of plasticity in the brain. Researchers reached different conclusions regarding the location of the critical period: 15 years (Patkowski, 1990), 12 years (Scovel, 1988), or even earlier. Long (1990) pointed out that a second language learner would achieve a native-like accent if the onset age is 6 years old, and would always maintain a foreign accent if the language was learnt after the age of 12, whereas if the learning process started within the period 6-12 years, the results may vary. An alternative hypothesis is the Sensitive Period Hypothesis (SPH), which advocates the existence of a sensitive period rather than a specific age. One of the first studies on this topic by Asher and García (1969) reflected on the optimal age to learn a second language. The subjects consisted of an experimental group of 71 Cuban immigrants between the ages of seven and nineteen, who had been in United States for five years, and a control group of thirty American children. The task was to read four English sentences which were replayed and judged by nineteen American high school students who had to decide if the speaker had a native pronunciation, near-native pronunciation, slight accent, or definite accent. The results showed that “if a child was under six when he came to the United States he had the highest probability of acquiring a near-native pronunciation of English and if the child was older than 13 he had the lowest chance of near-native speech” (337). However, none of the Cuban children achieved native English pronunciation, many acquired near-native speech, and an inverse relationship was found between age when the child entered the country and the acquisition of a near-native pronunciation. Flege, Munro, and Mackay (1995) assessed the degree of foreign accent in a group of 240 native Italian learners of English who had started learning the language in Canada between the ages of 2 and 23. Both the group of native Italian subjects and a control group of native English speakers were asked to read a number of English sentences. Then, the sentences were presented to linguistically naïve native English listeners who rated them using a continuous scale. A positive correlation was found between the onset age of learning and the degree of accentedness in pronunciation, accounting for an average of 59% of variance, whereas language use factors accounted for a 15%. Some judges were able to detect foreign accent in younger learners, but no Italian subject who had started learning English after the age of 15 was classified as a native-like speaker.
A way of testing the CPH would be proving the existence of speakers who started to learn the L2 as adults and still achieved a native-like oral competence. Bongaerts, van Summeren, Planken, and Schils (1997) carried out an experiment to investigate whether highly successful late learners would be rated as native speakers. The subjects were two groups of Dutch learners of English. The first group of subjects was composed of members who had an excellent command of British English pronunciation despite being late learners. The second group consisted of subjects whose English proficiency level varied and were supposed to have a foreign accent. There was also a comparison group of native speakers. The judges, who were native speakers of English, failed to make a distinction between the control group and the highly advanced learners. This study supports the claim that the acquisition of a native-like accent by late learners is plausible, but it “seems to be a fairly exceptional phenomenon” (462), since not all the highly successful learners in the study were acknowledged to have a native-like oral competence. The authors point out that a native like attainment in this case may be due to other factors regardless of maturational constrains such as greater neurocognitive flexibility than the normal population, very high motivation, or an enormous amount of input. Bongaerts replicated the study with Dutch learners of French (1999) in order to discover whether the results would be similar if the languages which were being compared were typologically less related. The design followed the first experiment: a control group of nine French speakers, a group of nine native speakers of Dutch who were considered exceptionally successful late learners, and a group of eighteen native speakers of Dutch whose levels of proficiency in their L2 varied. He found out that three out of nine highly successful learners were rated as native speakers of French. These experiments constitute a challenge for the CPH, and exemplify how ultimate attainment is possible. In consequence, having reached this point, it can be stated that age is not the only factor which determines oral proficiency; there must be other underlying causes, since what remains to be explained is what makes exceptional learners exceptional.
Experiments carried out so far prove that the earlier a person starts to learn the L2 the better his or her pronunciation will be (Asher and García, 1969; Krashen, Long, and Scarcella, 1979; Flege, Munro, and MacKay, 1995; Patkowski 1990; Piske, MacKay, and Flege, 2001). However, as we have seen, there is conflicting data concerning the existence of critical periods for learning an L2, i.e. Flege et al. (1995) vs. Bongaerts et al. (1997) and Bongaerts (1999). Besides, very different conclusions have been reached although it is a fairly specific topic: it has been claimed that all second language learners can attain a native-like accent, that only some L2 learners can, and that no L2 can. This suggests that other factors should be taken into account, and that “an interaction between maturational constraints an socio-psychological factors” (Hyltenstam & Abrahamsson, 2000: 163) may be assumed. Among the factors which can exert an influence over the degree of foreign accent we can list the following: aptitude, exposure to L2, training, first language influence, L1/L2 use, length of residence, gender, motivation, and teaching and learning method when learners receive formal instruction. Age of learning may be often confounded with these variables (Piske et al., 2001), since it is difficult to determine how each factor influences the others or how they can be studied independently.
Several studies looked at the influence of learner’s aptitude – learning or verbal ability – on L2 acquisition. Neufeld (1980) carried out a series of experiments focused on the relevance of learning ability in L2 acquisition. In the first experiment, seven non-native late learners of French and three native-speaking controls were asked to read a prepared corpus in French. The recordings were played to eighty-five French Canadians who had to decide if the speaker was francophone from Canada, francophone from another country, or not francophone. Five of them were qualified as native speakers. In the follow-up experiments, English subjects who were considered to have a foreign accent in French were given tape recordings to judge the degree of foreign accent in French. Anglophone speakers were highly sensitive in perception and the overall score for this group was slightly higher than the French-speaking judges who had performed the same task. Neufeld concluded that “there is frequent asymmetry in the adults’ receptive and productive performance in L2 at the phonological level” (295). Moreover, evidence was presented that adults are capable of acquiring a native-like accent in L2, and a native-like command of phonological rules. Finally, he argued that linguistic competence in L2 is a major factor in foreign accent recognition. DeKeyser (2000) designed a study to test Bley-Vroman’s (1988, 1989) Fundamental Difference Hypothesis, which states that whereas children are capable of learning a language implicitly, adults need to use different mechanisms to progress in their learning. Although this article is not centred on phonology, the author claimed that verbal ability makes a difference for adult learners since they require explicit learning processes. This view is not inconsistent with the existence of a critical period, but the relative importance of aptitude is acknowledged.
Another variable taken into consideration by researchers is L2 exposure and training. According to the Native Language Magnet Model (Iverson & Kuhl, 1995; Kuhl, 2000), infants shift from universal perception to language-specific perception by the age of 6 months. Perception is altered by language experience in the sense that “the language-specific filter alters the dimensions of speech we attend to, stretching and shrinking acoustic space to highlight the differences between language categories” (Kuhl, 2000: 11854). When learning an L2, speakers need a completely different mapping than the one they have for their mother tongue. Yet, adults are capable of distinguishing certain non-native phonemes even with little exposure, but fail to differentiate non-native phonemes when they constitute allophonic variation in their first language (Iverson et al., 2003). Studies on perception have shown that production is based on imitation, hence depends on perception, and both skills can be improved by means of appropriate training. An experiment designed by Wang and Kuhl (2003) assessed the perceptual learning of lexical tones in Mandarin Chinese by American speakers – children and young adults –. The results showed significant improvement after two-week training for both children and adults, and no rigid cut off periods were observed, pointing out that “given the same amount of exposure, the degree of learning would be the same regardless of age” (1539). If we accept that speakers have a different mapping depending on their first language, it would be logical to take for granted that L1 would have an effect on oral proficiency in L2. Flege (1999) reports a speech perception study by Rochet (1995) where a synthetic continuum of the vowels /i/ – /y/ – /u/ was used to investigate how non-native speakers categorised these phonemes. The results indicated that native speakers of Portuguese identified /y/ as /i/; on the contrary, English participants classified /y/ as /u/. This experiment corroborates that L1 phonology is unequivocally connected to the acquisition of L2, and further research should be done to clarify how the phonological system of L1 affects L2 production accuracy. In relation to this factor, we can proceed to the next variable, L1 use. Flege, Frieda, and Nozawa (1997) tackled this topic in a study which pursued to establish whether the differences in the amount L1 use affected L2 oral proficiency. The subjects were drawn from Flege et al. (1995) and were assigned to three different groups according to their use of Italian – their L1 –: native speakers, low use, and high use. The results showed that “the native Italian subjects who continued to speak their L1 relatively often had signiﬁcantly stronger foreign accents in English than did the subjects who seldom spoke Italian” (182). In addition, all the participants had moved to the English speaking country, Canada, before the age of 10 years. Flege suggested that “one’s accuracy in pronouncing an L2 varies as a function of how well one pronounces the L1, and how often one speaks the L1” (1999). Once again, evidence shows that the critical period, or age itself, cannot account for all the variance in L2 oral competence.
Length of residence in the country where the L2 is spoken is the variable which has been examined most frequently after age of learning, but it is “a less important predictor of degree of L2 foreign accent” (Piske et al., 2001: 199). With regard to gender, in Asher and García (1967) evidence was found that more girls than boys acquired near-native pronunciation, but the difference “tended to diminish the longer the children lived in the United States […] in time the sex difference seemed to vanish” (341). Gender was also taken into consideration in Flege, Munro, and Mackay’s study (1995), but it did not lead to any definitive conclusions. The same can be said about other papers which reflected on this variable. As mentioned before, motivation plays an important role in L2 acquisition. Nevertheless, it’s not clear to what extent it is related to the other factors. In Bongaerts et al. (1997) and Bongaerts (1999), the participants who were regarded as highly successful learners with a native-like accent had reported that having an accent-free pronunciation was essential for their job. As far as formal instruction is concerned, the nature of the teaching and learning process is vital to the acquisition of the oral competence. Even though the current dominant approach for foreign language teaching is the Communicative Approach, which advocates the prioritisation of the oral skills (Larsen-Freeman, 2000), pronunciation may be disregarded in foreign language classrooms, since other aspects of languages might be considered more accessible. That may be the reason why “there is little evidence to date that amount of formal instruction as such affects the degree of L2 foreign accent” (Piske et al., 2001:201). Nonetheless, as we have seen in studies such as Bongaerts et al (1997), or Wang and Kuhl (2003) specialised training has a biggerr effect on L2 pronunciation.
This essay examined whether L2 perception and production accuracy could be accounted for by age of learning; first, looking at the reasons why age of learning may be the most important factor, and then, alluding to other variables. As we have seen from the different studies, the existence of a critical period for language learning, or the fact that younger learners outperform older ones in L2 production, is not sufficient to explain variability in L2 oral proficiency. Thus, oral proficiency is not entirely determined by age; rather, there are multiple factors which should be taken into consideration, such as learning ability, exposure to L2, training, first language influence, L1/L2 use, length of residence, gender and motivation. The fact that children have an advantage over adults when learning an L2 is widely agreed; however, it does not imply that they always achieve ultimate attainment, or that adults cannot do it. It is worth mentioning that this initial advantage is not only due to maturational constrains, but also to other factors which facilitate this acquisition, i.e. simplified input, or education opportunities (Bialystok & Hakuta, 1999). Furthermore, “there may well be a range of aspects of second language acquisition where adults have an advantage over children” (Hyltenstam & Abrahamsson, 2000: 154), since there are tasks in which adults do outperform children. In conclusion, it could be said that in order to account for oral proficiency in second language acquisition, not only age, but all the factors mentioned should be taken into account, and all of them need to be analysed to design a comprehensive theory, as “the adult second language learner who has attained native-like proficiency probably exists but is yet to be described in the scientific literature” (162).
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