User:Mga/Second Language Acquisition

How children acquire native language (L1) and the relevance of this to foreign language (L2) learning has long been debated. Although evidence for L2 learning ability declining with age is controversial, a common notion is that children learn L2s easily, whilst older learners rarely achieve fluency. This assumption stems from ‘critical period’ (CP) ideas. A CP was originally postulated by Lenneberg (1967) for L1 acquisition, but considerable interest now surrounds age effects on second language acquisition (SLA). SLA theories explain learning processes and suggest causal factors for a possible CP for SLA, mainly attempting to explain apparent differences in language aptitudes of children and adults by distinct learning routes, and clarifying them through psychological mechanisms (Mitchell and Myles, 1998). Research explores these ideas and hypotheses, but results are varied: some demonstrate pre-pubescent children acquire language easily, and some that older learners have the advantage, whilst others focus on existence of a CP for SLA (B. Harley, 1986). Recent studies (e.g. Mayberry and Lock, 2003) have recognised certain aspects of SLA may be affected by age, whilst others remain intact. The objective of this study is to investigate whether capacity for vocabulary acquisition decreases with age. A review of SLA theories and their explanations for age-related differences is necessary before considering empirical studies. The most reductionist theories are those of Penfield and Roberts (1959) and Lenneberg (1967), which stem from L1 and brain damage studies; children who suffer impairment before puberty typically recover and (re-)develop normal language, whereas adults rarely recover fully, and often do not regain verbal abilities beyond the point reached five months after impairment (Hurford, 1991). Both theories agree that children have a neurological advantage in learning languages, and that puberty correlates with a turning point in ability. They assert that language acquisition occurs primarily, possibly exclusively, during childhood as the brain loses plasticity after a certain age. It then becomes rigid and fixed, and loses the ability for adaptation and reorganisation, rendering language (re-)learning difficult. Penfield and Roberts (1959) claim children under nine can learn up to three languages: early exposure to different languages activates a reflex in the brain allowing them to switch between languages without confusion or translation into L1 (Penfield, 1964). Lenneberg (1967) asserts that if no language is learned by puberty, it cannot be learned in a normal, functional sense. He also supports Penfield and Roberts’ (1959) proposal of neurological mechanisms responsible for maturational change in language learning abilities. This, Lenneberg maintains, coincides with brain lateralisation and left-hemispherical specialisation for language around age thirteen: infants’ motor and linguistic skills develop simultaneously, but by age thirteen the cerebral hemispheres’ functions separate and become set, making language acquisition extremely difficult (Lenneberg, 1967).

Cases of deaf and feral children provide evidence for a biologically determined CP for L1. Feral children are those not exposed to language in infancy/childhood due to being brought up in the wild, in isolation and/or confinement. A classic example is Genie (Curtiss, 1977), who was deprived of social interaction from birth until discovered aged thirteen (post-pubescent). She was completely without language, and after seven years of rehabilitation still lacked linguistic competence. Another case is ‘Isabelle’, who was incarcerated with her deaf-mute mother until the age of six and a half (pre-pubescent). She also had no language skills, but, unlike Genie, quickly acquired normal language abilities through systematic specialist training (Davies, 1949). Such studies are however problematic; isolation can result in general retardation and emotional disturbances, which may confound conclusions drawn about language abilities. Studies of deaf children learning American Sign Language (ASL) have fewer methodological weaknesses. Newport and Supalla (1987) studied ASL acquisition in deaf children differing in age of exposure; few were exposed to ASL from birth, most of them first learned it at school. Results showed a linear decline in performance with increasing age of exposure; those exposed to ASL from birth performed best, and ‘late learners’ worst, on all production and comprehension tests. Their study thus provides direct evidence for language learning ability decreasing with age, but it does not add to Lennerberg’s CP hypothesis as even the oldest children, the ‘late learners’, were exposed to ASL by age four, and had therefore not reached puberty, the proposed end of the CP. In addition, the declines were shown to be linear, with no sudden ‘drop off’ of ability at a certain age, as would be predicted by a strong CP hypothesis. That the children performed significantly worse, however, suggests the CP may end earlier than originally postulated. Other work has challenged the biological approach; Witelson (1977) concludes that lateralisation is complete by age five. Likewise, Krashen (1975) reanalysed clinical data used as evidence and concluded cerebral specialisation occurs much earlier than Lenneberg calculated. Therefore, if a CP exists, it does not coincide with lateralisation. Despite concerns with Lenneberg’s original evidence and the dissociation of lateralisation from the language CP idea, however, the concept of a CP remains a viable hypothesis, which later work has better explained and substantiated. Contrary to biological views, behavioural approaches assert that languages are learned as any other behaviour, through conditioning. Skinner (1957) details how classical conditioning forms connections with the environment through interaction and, alongside Mowrer (1960), applies the ideas to language acquisition. Mowrer hypothesises that languages are acquired through rewarded imitation of ‘language models’; the model must have an emotional link to the learner (e.g. parent, spouse), as imitation then brings pleasant feelings which function as positive reinforcement. Because new connections between behaviour and the environment are formed and reformed throughout life, it is possible to gain new skills, including language(s), at any age. To accommodate observed language learning differences between children and adults, Felix (1985) describes that children, whose brains create countless new connections daily, may handle the language learning process more effectively than do adults. This assumption, however, remains untested and is not a reliable explanation for children’s aptitude for L2 learning (Ellis, 1985). Problematic of the behaviourist approach is its assumption that all learning, verbal and non-verbal, occurs through the same processes (Chomsky, 1959). A more general problem is that, as Pinker (1995) notes, almost every sentence anybody voices is an original combination of words, never previously uttered, therefore a language cannot consist only of word combinations learned through repetition and conditioning; the brain must contain innate means of creating endless amounts of grammatical sentences from a limited vocabulary. This is precisely what Chomsky (1965) argues with his proposition of a Universal Grammar (UG).

Chomsky (1965) asserts that environmental factors must be relatively unimportant for language emergence, as so many different factors surround children acquiring L1. Instead, Chomsky claims language learners possess innate principles building a ‘language acquisition device’ (LAD) in the brain. These principles denote restricted possibilities for variation within the language, and enable learners to construct a grammar out of ‘raw input’ collected from the environment (Mitchell and Myles, 1998). Input alone cannot explain language acquisition because it is degenerated by characteristic features such as stutters, and lacks corrections from which learners discover incorrect variations. Singleton and Newport (2004) demonstrate the function of UG in their study of ‘Simon’. Simon learned ASL as his L1 from parents who had learned it as an L2 after puberty and provided him with imperfect models. Results showed Simon learned normal and logical rules and was able to construct an organised linguistic system, despite being exposed to inconsistent input. Chomsky developed UG to explain L1 acquisition data, but maintains it also applies to L2 learners who achieve near-native fluency not attributable solely to input and interaction (Chomsky, 1965). Although it does not describe an optimal age for SLA, the theory implies that younger children can learn languages more easily than older learners, as adults must reactivate principles developed during L1 learning and forge an SLA path: children can learn several languages simultaneously as long as the principles are still active and they are exposed to sufficient language samples (Pinker, 1995). The parents of Singleton and Newport’s (2004) patient also had linguistic abilities in line with these age-related predictions; they learned ASL after puberty and never reached complete fluency.

There are, however, problems with the extrapolation of the UG theory to SLA: L2 learners go through several phases of types of utterance that are not similar to their L1 or the L2 they hear. Other factors include the cognitive maturity of most L2 learners, that they have different motivation for learning the language, and already speak one language fluently (Mitchell and Myles, 1998). Other studies also highlight these problems: Deheane (1999) investigates how cerebral circuits used to handling one language adapt for the efficient storage of two or more. He reports Price, Green and von Studnitz’s (1999) observations of cerebral activation when reading and translating two languages. They found the most activated brain areas during the tasks were not those generally associated with language, but rather those related to mapping orthography to phonology. They conclude that the left temporal lobe is the physical base of L1, but the L2 is ‘stored’ elsewhere, thus explaining cases of bilingual aphasia where one language remains intact (e.g. Hakuta, 1986). They maintain that only languages learned simultaneously from birth are represented, and cause activity, in the left hemisphere: any L2 learned later is stored separately (Martin, 1998, cited in T. Harley, 2001, suggests in the right hemisphere), and rarely activates the left temporal lobe. This suggests that L2 may be qualitatively different to L1 due to its dissociation from the ‘normal’ language brain regions, thus the extrapolation of L1 studies and theories to SLA is placed in question. A further disadvantage of UG is that supporting empirical data are taken from a limited sample of syntactic phenomena: a general theory of language acquisition should cover a larger range of phenomena (B. Harley, 1986). Despite these problems, several other theorists have based their own models of language learning on it; amongst others Felix’ (1985) ‘competing cognitive systems’ idea, and Dulay and Burt’s (1974) ‘creative construction theory’. These ideas are supported by empirical evidence, which consequently supports Chomsky’s ideas. Due to this support and its descriptive and explanatory strength, many theorists regard UG as the best explanation of language, and particularly grammar, acquisition.

Piaget (1926, cited in Mitchell and Myles, 1998) is one psychologist reluctant to ascribe specific innate linguistic abilities to children: he considers the brain a homogenous computational system, with language acquisition being one part of general learning. He agrees this development may be innate, but claims there is no specific language acquisition module in the brain. Instead, he suggests external influences and social interaction trigger language acquisition: information collected from these sources constructs symbolic and functional schemata (thought or behaviour patterns). According to Piaget, cognitive development and language acquisition are life-long active processes that constantly update and re-organise schemata. He proposes children develop L1 as they build a sense of identity in reference to the environment, and describes phases of general cognitive development, with processes and patterns changing systematically with age (Mitchell and Myles, 1998). Piaget assumes language acquisition is part of this complex cognitive development, and that these developmental phases are the basis for an optimal period for language acquisition in childhood (Twyford, 1988). Interactionist approaches derived from Piaget’s ideas supports his theory. Some studies (e.g. Newport and Supalla, 1987) show that, rather than abrupt changes in SLA ability after puberty, language ability declines with age, coinciding with declines in other cognitive abilities, thus supporting Piaget. Several researchers, however, remain unconvinced that language acquisition is part of general development: Felix (1981) claims cognitive abilities alone are useless for language learning, as only vocabulary and meaning are connected to cognition; lexicology and related meanings have conceptual bases. Felix’ criticism of the assumption that L2 fluency simply requires skilful applications of the correct rules is supported by the lack of psychological empirical evidence for Piaget’s idea. Although Krashen (1973) also criticises this theory, neither discredit the importance of age for second language acquisition. Krashen (1975), and later Felix (1981), proposed theories for the close of the CP for L2 at puberty, based on Piaget’s cognitive stage of formal operations beginning at puberty, as the ‘ability of the formal operational thinker to construct abstract hypotheses to explain phenomena’ inhibits the individual’s natural ability for language learning (B. Harley, 1986, p. 9). Krashen’s (1985) Monitor Model is a nativist, comprehension based approach. The theory consists of five hypotheses, which describe different aspects of SLA: the acquisition-learning hypothesis, the monitor hypothesis, the natural order hypothesis, the input hypothesis and the affective filter hypothesis. The acquisition-learning distinction is the most fundamental of these and the most widely known among linguists. According to Krashen (1985) these are two independent systems of L2 performance; acquisition is a product of subconscious processing similar to children’s L1 acquisition and requires life-like L2 interaction, which focuses on communication not correctness, while learning occurs through formal instruction and comprises conscious processing, which results in knowledge about the L2, e.g. grammatical rules. Krashen (1983) believes ‘learned competence’ acts as a monitor or editor: that is, whereas ‘acquired competence’ is responsible for the fluent production of sentences, ‘learned competence’ consciously corrects them. He claims that learned knowledge enables learners to read and listen more, so acquisition is effective. The monitor hypothesis asserts that learners’ emotional states act as adjustable filters that freely permit or hinder input necessary to acquisition. He suggests that adolescence and puberty are not good periods for SLA, as this ‘affective filter’ arises out of self-conscious reluctance to reveal oneself and feelings of vulnerability. The Monitor Model then predicts faster initial progress by adults than children, as adults use this ‘monitor’ when producing L2 utterances before having acquired the ability for natural performance, and adults will input more into conversations earlier than children. However, in the long term, SLA started in childhood will be superior in ultimate attainment as children will already have control of some L2 acquired before pubertal changes began inhibiting learning. The model has been criticised by some linguists: McLaughlin (1987) claims that none of the hypotheses is clear in its prediction, for example, the acquisition-learning distinction is not properly defined and the distinction cannot be empirically tested. However, continued interest in Krashen’s theory indicates this theory is far from pseudo-scientific. In determining an optimal SLA age, the variables these theories propose are not the only possibilities: affective factors, including motivation and fear, also influence language-learning attitudes. These factors can explain maturational differences in SLA: older learners often learn new languages for economical or academic reasons, and therefore work harder to reach their target fluency. Such motivation is absent in children and may therefore result in slow SLA in school (Schumann, 1978). In contrast, children successfully learn languages naturally due to intrinsic motivation to partake in peer-group activities. Learning a new language, for some people, is also connected with fear (Dulay, Burt and Krashen, 1982). As previously discussed, Krashen (1975) explains how a ‘fear barrier’ can inhibit young peoples’ (not children) L2 achievement problems (as reported by Cummins, 1981); a fear of failing or appearing foolish and a self-conscious reluctance to reveal themselves creates an emotional filter, blocking achievement of their full potential.

Empirical research has attempted to account for variables detailed by SLA theories and provide an insight into L2 learning processes, which can be applied in educational environments. Recent SLA investigations have followed two main directions: one focuses on pairings of L1 and L2 that render L2 acquisition particularly difficult, and the other investigates certain aspects of language that may be maturationally constrained. Flege, Mackay and Piske (2002) looked at bilingual dominance to evaluate two explanations of L2 performance differences between bilinguals and monolingual-L2 speakers, i.e. a maturationally defined CP or interlingual interference. They investigated whether the age at which participants learned English affected dominance in Italian-English bilinguals, and found the early bilinguals were English (L2) dominant and the late bilinguals Italian (L1) dominant. Further analysis showed that dominant Italian bilinguals had detectable foreign accents when speaking English, but early bilinguals (English dominant) had no accents in either language. This suggests that, whilst interlingual interference effects are not inevitable, their emergence, and bilingual dominance, may be related to a CP. Sebastián-Gallés, Echeverría and Bosch (2005) also studied bilinguals and highlight the importance of early language exposure. They looked at vocabulary processing and representation in Spanish-Catalan bilinguals exposed to both languages simultaneously from birth in comparison to those who had learned L2 later and were either Spanish- or Catalan-dominant. Findings showed ‘from birth bilinguals’ had significantly more difficulty distinguishing Catalan words from non-words differing in specific vowels than Catalan-dominants did (measured by reaction time). These difficulties are attributed to a phase around age eight months where bilingual infants are insensitive to vowel contrasts, despite the language they hear most. This affects how words are later represented in their lexicons, highlighting this as a decisive period in language acquisition and showing that initial language exposure shapes linguistic processing for life. Sebastián-Gallés et al (2005) also indicate the significance of phonology for L2 learning; they believe learning an L2 once the L1 phonology is already internalised can reduce individuals’ abilities to distinguish new sounds that appear in the L2.

Most studies into age effects on specific aspects of SLA have focused on grammar, with the common conclusion it is highly constrained by age, more so than semantic functioning. B. Harley (1986) compared attainment of French learners in early and late immersion programs. She reports that after 1000 exposure hours, late learners had better control of French verb systems and syntax. However, comparing early immersion students (average age 6.917 years) with age-matched native speakers identified common problem areas, including third person plurals and polite ‘vous’ forms. This suggests grammar (in L1 or L2) is generally acquired later, possibly because it requires abstract cognition and reasoning (B. Harley, 1986). B. Harley also measured eventual attainment and found the two age groups made similar mistakes in syntax and lexical selection, often confusing French with the L1. The general conclusion from these investigations is that different aged learners acquire the various aspects of language with varying difficulty. Some variation in grammatical performance is attributed to maturation (discussed in B. Harley, 1986), however, all participants began immersion programs before puberty and so were too young for a strong critical period hypothesis to be directly tested. More recently Mayberry and Lock (2003) questioned whether age restrains both L1 and L2 acquisition. They examined grammatical abilities of deaf and hearing adults who had their initial linguistic exposure either in early childhood or later. They found that, on L2 grammatical tasks, those who had acquired the verbal or signed L1 early in life showed near-native performance and those who had no early L1 experience (i.e. born deaf and parents did not know sign-language) performed weakly. Mayberry and Lock concluded early L1 exposure is vital for forming life-long learning abilities, regardless of the nature of the exposure (verbal or signed language). This corresponds to Chomsky’s UG theory, which states that whilst language acquisition principles are still active, it is easy to learn a language, and the principles developed through L1 acquisition are vital for learning an L2. Scherag, Demuth, Rösler, Neville and Röder (2004) also suggest learning some syntactic processing functions and lexical access may be limited by maturation, whereas semantic functions are relatively unaffected by age. They studied the effect of late SLA on speech comprehension by German immigrants to the U.S.A. and American immigrants to Germany. They found that native-English speakers who learned German as adults were disadvantaged on certain grammatical tasks whilst performing at near-native levels on lexical tasks. These findings are consistent with work by Hahne (2001, cited in Scherag et al, 2004).

One study that specifically mentions semantic functions acquisition is that of Weber-Fox and Neville (1996). Their results showed that Chinese-English bilinguals who had been exposed to English after puberty, learned vocabulary to a higher competence level than syntactic aspects of language. They do, however, report that the judgment accuracies in detecting semantic anomalies were altered in subjects who were exposed to English after sixteen years of age, but were affected to a lesser degree than were grammatical aspects of language. It has been speculated (Neville and Bavelier, 2001, and Scherag et al, 2004) that semantic aspects of language are founded on associative learning mechanisms, which allow life-long learning, whereas syntactical aspects are based on computational mechanisms, which can only be constructed during certain age periods. Consequently, it is reasoned, semantic functions are easier to access during comprehension of an L2 and therefore dominate the process: if these are ambiguous, understanding of syntactic information is not facilitated. These suppositions would help explain the results of Scherag et al’s (2004) study.

Some researchers have focused exclusively on practical applications of SLA research. Asher (1972) insists teenagers and adults rarely successfully learn an L2, and attributes this to teaching strategies. He presents an L2 teaching strategy based on infants’ L1 acquisition, which promotes listening as central in language learning: listening precedes, and generates a ‘readiness’ for, speaking, assumptions supported by Carroll (1960). Asher shows that in L2 acquisition, in this case German, listening fluency is achieved in around half the usual time if the teaching is based on L1 acquisition, and that learners taught in this way still develop reading and writing proficiency comparable with those whose training emphasises literacy skills. Similarly Horwitz (1986) summarises findings of SLA research, and applies to L2 teaching some principles of L2 acquisition honed from a vast body of relevant literature. Like Asher, Horwitz highlights the importance of naturalistic experience in L2, promoting listening and reading practice and stressing involvement in life-like conversations. She explicitly suggests teaching practices based on these principles; ‘[m]uch class time should be devoted to the development of listening and reading abilities’, and ‘[t]eachers should assess student interests and supply appropriate…materials’ (Horwitz, 1986, p.685-686). The ‘audio-lingual’ teaching practices used in the present study are based on principles explicated by Asher and Horwitz; listening featured heavily, closely followed by reading and speaking practice. The vocabulary items taught were deemed relevant for all learners, regardless of age, and, according to Pfeffer (1964), they are among the most common used nouns in everyday German language.