Second-language acquisition

Second language acquisition, or SLA, is the academic discipline concerned with the study of the processes by which people learn languages in addition to their native tongue. The term SLA has become standard for referring to all research on non-native language learning, even when the language learned is a learner's third or fourth. The language to be learned is often referred to as the "target language," or as the "L2.".

The term "language acquisition" became commonly used after Stephen Krashen contrasted it with formal and non-constructive "learning." Today, most scholars in the field use "language learning" and "language acquisiton" interchangeably, unless they are directly addressing Krashen's work. However, "Second Language Acquisition" or "SLA" has become established as the preferred term for this academic discipline.

Describing learner language

Through the descriptive study of learner language, SLA researchers seek to better understand the process of language learning without recourse to factors outside learner language. Researchers in this area may adopt an interlanguage perspective, exploring learner language as a linguistic system, or they may study how learner language compares to the target language. Research in this area is centered on the question: What are the unique characteristics of learner language?

Error analysis

The field of error analysis in SLA was established in the 1970s by S.P. Corder and colleagues. A widely-available survey of the field can be found in chapter 8 of Brown, 2000. Error analysis was an alternative to the existing field of contrastive analysis, a technique influenced by behaviorism through which applied linguists sought to use the formal distinctions between the learners' first and second languages to predict errors. Studies in error analysis showed that contrastive analysis was unable to predict a great majority of errors, although its more valuable aspects have been incorporated into the study of language transfer. A key finding of error analysis has been that many learner errors are produced by learners making faulty inferences about the rules of the new language.

Error analysts distinguish between errors, which are systematic, and mistakes, which are not. They often seek to develop a typology of errors. Error can be classified according to basic type: omissive, additive, substitutive or related to word order. They can be classified by how apparent they are: overt errors such as "I angry" are obvious out of context, whereas covert errors are evident only in context. Closely related to this is the classification according to domain, the breadth of context which the analyst must examine, and extent, the breadth of the utterance which must be changed in order to fix the error. Errors may also be classified according to the level of language: phonological errors, vocabulary or lexical errors, syntactic or grammatical errors, and so on. They may be assessed on the degree to which they interfere with communication: global errors make an utterance difficult to understand, while local errors do not interfere with understanding. In the above example, "I angry" would be a local error, since the meaning is apparent.

From the beginning, error analysis was beset with methodological problems. In particular, the above typologies are problematic: it is often impossible to reliably determine what kind of error a learner is making, based on linguistic data alone. Also, error analysis can deal effectively only with learner production (speaking and writing) and not with learner reception (listening and reading). Furthermore, it cannot control for learner use of communicative strategies such as avoidance, in which learners simply do not use a form with which they fell uncomfortable. For these reasons, although error analysis is still used to investigate specific questions in SLA, the quest for an overarching theory of learner errors has largely been abandoned. In the mid-1970s, Corder and others moved on to a more wide-ranging approach to learner language, known as interlanguage.

Error analysis is closely related to the study of error treatment in language teaching. Today, the study of errors is particulary relevant for focus on form teaching methodology.

Interlanguage

Interlanguage scholarship seeks to understand learner language on its own terms, as a natural language with its own consistent set of rules. Interlanguage scholars reject, at least for heuristic purposes, the view of learner language as merely an imperfect version of the target language. Interlanguage is perhaps best viewed as a point of view on language acquisition, and not a distinct discipline. By the same token, interlanguage work is a vibrant microcosm of linguistics. It is possible to apply an interlanguage perspective to learner pronunciation (interlanguage phonology), but also to language-use norms found among learners (interlanguage pragmatics).

By describing the ways in which learner language conforms to universal linguistic norms, interlanguage research has contributed greatly to our understanding of linguistic universals in SLA. See below, under "linguistic univerals".

Developmental patterns

Ellis (1994) introduced the terminology of "order" to refer to the pattern in which different language features are acquired, and "sequence" to denote the pattern by which a specific language feature is acquired.

Order of acquisition

Researchers have found a very consistent order in the acquisition of first language structures by children, and this has drawn a great deal of interest from SLA scholars. Considerable scholarship has been devoted to testing the "identity hypothesis," which asserts that first-language and second-language acquisition conform to the same patterns. The equivalence hypothesis has not been confirmed, probably because second-language learners' cognitive and affective states are so much more advanced. However, orders of acquisition in SLA do often resemble those found in first language acquisition, and may have common neurological causes.

Most learners begin their acquisition process with a "silent period," in which they speak very little if at all. In some cases this is a period of language shock, in which the learner actively rejects the incomprehensible input of the new language. However, research has shown that many "silent" learners are engaging in private speech (sometimes called "self-talk"). While appearing silent, they are rehearsing important survival phrases and lexical chunks. These memorized phrases are then employed in the subsequent period of formulaic speech. Some learners, by choice or compulsion, have no silent period and pass directly to formulaic speech. Formulaic speech, in which a handful of routines are used to accomplish basic purposes, is often highly grammatical. It eventually gives way to a more experimental phase of acquisition, in which the semantics and syntax of the target language are simplified and the learners begin to construct a true interlanguage.

The nature of the transition between formulaic and simplied speech is disputed. Some, including Krashen, have argued that there is no cognitive relationship between the two, and that the transition is abrupt. Thinkers influenced by recent theories of the lexicon have preferred to view even native speaker speech as heavily formulaic, and interpret the transition as a process of gradually developing a broader repertoire of chunks and a deeper understanding of the rules which govern them. Some studies have supported both views, and it is likely that the relationship depends in great part on the learning styles of individual learners.

A flurry of studies took place in the 1970s, examining whether a consistent order of acquisition could be shown for morphological aspects of language. Most of these studies did show fairly consistent orders of acquisition for selected morphemes. For example, among learners of English the cluster of features including the suffix "-ing," the plural, and the copula were found to consistently precede other features such as the article, auxiliary, and third person singular. However, these studies were widely criticized as not paying sufficient attention to the details of acquisition, such as the degree of mastery that learners had gained over a specific feature. More recent scholarship prefers to view the acquisition of each linguistic feature as a gradual and complex process. For that reason most scholarship since the 1980s has focused on the sequence, rather than the order, of feature acquisition.

Sequence of acquisition

A number of studies have looked into the sequence of acquisition of pronouns by learners of various Indo-European languages. These are reviewed by Ellis (1994), pp. 96-99. They show that learners begin by omitting pronouns or using them indiscriminately: for example, using "I" to refer to all agents. Learners then acquire a single pronoun feature, often person, followed by number and eventually by gender. Very little evidence of interference from the learner's first language has been found; it appears that learners use pronouns based entirely on their inferences about target language structure.

Studies on the acquisition of word order in German have shown that most learners begin with a word order based on their native language. This indicates that certain aspects of interlanguage syntax are influenced by the learners' first language, although others are not.

Research on the sequence of acquisition of words is exhaustively reviewed by Nation (2001). Research on the sequence of acquisition of pragmatic features, although much more scarce, has been thoroughly examined by Kasper and Rose (2002). In both fields, consistent patterns have emerged and have been the object of considerable theorizing.

Variability

Valid though the interlanguage perspective may be, which views learner language as a language in its own right, this language varies much more than native-speaker language, in an apparently chaotic way. A learner may exhibit very smooth, grammatical language in one context and uninterpretable gibberish in another. Scholars from different traditions have taken opposing views on the importance of this phenomenon. Those who bring a Chomskyan perspective to SLA typically regard variability as nothing more than "performance errors," and not worthy of systematic inquiry. On the other hand, those who approach it from a sociolinguistic or psycholinguistic orientation view variability as a key indication of how the situation affects learners' language use. Naturally, most research on variability has been done by those who presume it to be meaningful.

Research on variability in learner language distinguishes between "free variation," which takes place even within the same situation, and "systematic variation," which correlates with situational changes. Of course, the line between the two is often subject to dispute.

Free variation, variation without any determinable pattern, is itself highly variable from one learner to another. To some extent it may indicate different learning styles and communicative strategies. Learners that favor high-risk communicative strategies and have an other-directed cognitive style are more likely to show substantial free variation, as they experiment freely with different forms.

Free variation in the use of a language feature is usually taken as a sign that it has not been fully acquired. The learner is still trying to figure out what rules govern the use of alternate forms. This type of variability seems to be most common among beginning learners, and may be entirely absent among the more advanced.

Systematic variation is brought about by changes in the linguistic, psychological, social context. Linguistic factors are usually extremely local. For instance, the pronunciation of a difficult phoneme may vary based on whether it is to be found at the beginning of a word or the end.

Social factors may include a change in register or the familiarity of interlocutors. In accordance with speech accommodation theory, learners may adapt their speech to either converge with, or diverge from, their interlocutor's usage.

The most important psychological factor is usually taken to be planning time. As numerous studies have shown, the more time that learners have to plan, the more regular and complex their production is likely to be. Thus, learners may produce much more target-like forms in a writing task for which they have 30 minutes to plan, than they do in conversation where they must produce language with almost no planning at all.

Affective factors also play an important role in systematic variation. For example, learners in a stressful situation (such as a formal exam) may exhibit much less target-like forms than they would in a comfortable setting. This clearly interacts with social factors, and attitudes toward the interlocutor and topic also play important roles.

Learner-external factors

The study of learner-external factors in SLA is primarily concerned with the question: How do learners get information about the target language? Study has focused on the effects of different kinds of input, and on the impact of the social context.

Social effects

The process of language learning can be very stressful, and the impact of positive or negative attitudes from the surrounding society can be critical. One aspect of this which has received particular attention is the relationship of gender roles to language achievement. Studies across numerous cultures have shown that women, on the whole, enjoy an advantage over men. Some have proposed that this is linked to gender roles.

Community attitudes toward the language being learned can also have a profound impact on SLA. Where the community has a broadly negative view of the target language and its speakers, or a negative view of its relation to them, learning is typically much more difficult. This finding has been confirmed by research in numerous contexts. A widely-cited example is the difficulty faced by Navajo children in learning English as a second language.

Other common social factors include the attitude of parents toward language study, and the nature of group dynamics in the language classroom.

Input and intake

Learners' most direct source of information about the target language is the target language itself. When learners come into direct contact with the target language, this is referred to as "input." When learners process that language in a way that can contribute to learning, this is referred to as "intake."

Generally speaking, the amount of input learners take in is one of the most important factors affecting their learning. However, it must be at a level that is comprehensible to them. In his Monitor Model, Krashen advanced the concept that language input should be at the "L+1" level, just beyond what the learner can fully understand; this input is comprehensible, but contains structures that are not yet fully understood. This has been criticized on the basis that there is no clear definition of L+1, and that factors other than structural difficulty (such as interest or presentation) can affect whether input is actually turned into intake. The concept has been quantified, however, in vocabulary acquisition research; Nation (2000) reviews various studies which indicate that about 98% of the words in running text should be previously known in order for extensive reading to be effective.

A great deal of research has taken place on input enhancement, the ways in which input may be altered so as to direct learners' attention to linguistically important areas. Input enhancement might include bold-faced vocabulary words or marginal glosses in a reading text. Research in this field is closely linked to research on pedagogical effects, and comparably diverse.

Interaction

The interaction hypothesis proposes that language acquisition is strongly facilitated by the use of the target language in interaction. In particular, the negotiation of meaning has been shown to contribute greatly to the acquisition of vocabulary. In a review of the substantial literature on this topic, Nation (2000) relates the value of negotiation to the generative use of words: the use of words in new contexts which stimulate a deeper understanding of their meaning.

In the 1980s, Canadian SLA researcher Merrill Swain advanced the output hypothesis, that meaningful output is as necessary to language learning as meaningful input. However, most studies have shown little if any correlation between learning and quantity of output. Today, most scholars in the field contend that small amounts of meaningful output are important to language learning, but primarily because the experience of producing language leads to more effective processing of input.

Pedagogical effects

The study of the effects of teaching on second language acquisition seeks to systematically measure or evaluate the effectiveness of language teaching practices. Such studies have been undertaken with respect to every level of language, from phonetics to pragmatics, and almost every current teaching methodology. It would be absurd, therefore, to attempt to summarize their findings here. However, some more general issues have been addressed.

Research has indicated that many traditional language-teaching techniques are extremely inefficient. However, today a broad consensus of SLA scholars, acknowledge that formal instruction can play a significant constructive role in language learning.

Another important issue is the effectiveness of explicit teaching: can language teaching have a constructive effect beyond providing learners with enhanced input? Because explicit instruction must usually take place in the learner's first language, many have argued that it simply starves learners of input and opportunities for practice. Research on this at different levels of language has produced quite different results. Most notably, pronunciation does not show any significant response to explicit teaching. Other traditional areas of explicit teaching, such as grammar and vocabulary, have had decidedly mixed results. The positive effect of explicit instruction at this level seems to be limited to helping students notice important aspects of input. Interestingly, the higher-level aspects of language such as sociopragmatic and discourse competence have shown the most consistently strong effects from explicit instruction. Research has also shown a distinct effect of age on the effectiveness of explicit instruction: the younger learners are, the less benefit they show.

Learner-internal factors

The study of learner-internal factors in SLA is primarily concerned with the question: How do learners gain competence in the target language? In other words, given effective input and instruction, with what internal resources do learners process this input to produce a rule-governed interlanguage?

Cognitive approaches

A great deal of research and speculation has taken place on the cognitive processes underlying SLA. A noted researcher in this field is Ellen Bialystok, who has modelled the process of acquisition in terms of gaining increasing attentional control over language use. In other words, as the processes of word selection and utterance construction become increasingly automatic, learners' language ability also improves.

Language transfer

Language transfer typically refers to the learner's trying to apply rules and forms of the first language into the second language. The term can also include the transfer of features from one additional language to another (such as from a second to a third language), although this is less common.

The school of contrastive analysis, discussed above, sought to predict all learner errors based on language transfer. As subsequent research in error analysis and interlanguage structure showed, this project was flawed: most errors are not due to transfer, but to faulty inferences about the rules of the target language.

Transfer is an important factor in language learning at all levels. Typically learners begin by transferring sounds (phonetic transfer) and meanings (semantic transfer), as well as various rules including word order and pragmatics. As learners progress and gain more experience with the target language, the role of transfer typically diminishes.

Linguistic universals

Research on universal grammar (UG) has had a significant effect on SLA theory. In particular, scholarship in the interlanguage tradition has sought to show that learner languages conform to UG at all stages of development. A number of studies have supported this claim, although the evolving state of UG theory makes any firm conclusions difficult.

A key question about the relationship of UG and SLA is: is the language acquisition device posited by Chomsky and his followers still accessible to learners of a second language? Research suggests that it becomes increasingly inaccessible as learners age, hence the growing dependence on explicit teaching (see pedagogical effects above, and age below). In other words, although all learners' processing of language is governed by UG, older learners have great difficulty in gaining access to the target language's underlying rules from input alone.

Individual variation

Research on variation between individual learners seeks to address the question: Why do some learners do better than others? This question was first addressed by a flurry of studies in the 1970s, which are often labelled the "good language learner studies." These studies sought to identify the distinctive factors of successful learners. Although those studies are now widely regarded as insufficiently sophisticated, they did serve to identify a number of factors affecting language acquisition. More detailed research on many of these specific factors continues today.

Language aptitude

Tests of language aptitude have proven extremely effective in predicting which learners will be successful in learning. However, considerable controversy remains about whether language aptitude is properly regarded as a unitary concept, an organic property of the brain, or as a complex of factors including motivation and short-term memory. Research has generally shown that language aptitude is quite distinct from general aptitude or intelligence, as measured by various tests, and is itself fairly consistently measurable by different tests.

Language aptitude research is often criticized for being irrelevant to the problems of language learners, who must attempt to learn a language regardless of whether they are gifted for the task or not. This claim is reinforced by research findings that aptitude is largely unchangeable. In addition, traditional language aptitude measures such as the Modern Language Aptitude Test strongly favor decontextualized knowledge of the sort that is used in taking tests, rather than the sort that is used in conversation. For this reason relatively little research is carried out on aptitude today. However, operators of selective language programs such as the United States Defense Language Institute continue to use language aptitude testing as part of applicant screening.

Age

It is commonly believed that children are better suited to learn a second language than are adults. However, in general second language research has failed to support the critical period hypothesis, which argues that full language acquisition is impossible beyond a certain age. Even those who begin learning a language late in life are capable of gaining a high level of fluency. The only aspect of language which has been shown to follow the critical period hypothesis is accent: the overwhelming majority of those who begin learning a language after puberty are unable to acquire a native-like accent.

Strategy use

The effective use of strategies has been shown to be critical to successful language learning, so much so that Canale and Swain (1980) included "strategic competence" among the four components of communicative competence. Research in this field has also shown significant pedagogical effects. This has given rise to the teaching method known as "strategies-based instruction."

Strategies are commonly divided into learning strategies and communicative strategies, although there are other ways of categorizing them. Learning strategies are techniques used to improve learning, such as mnemonics or using a dictionary. Learners (and native speakers) use communicative strategies to get meaning across even when they don't have access to the correct language: for example, by using pro-forms like "thing," or non-linguistic means such as mime. Communicative strategies may not have any direct bearing on learning, and some strategies such as avoidance (not using a form with which one is uncomfortable) may actually hinder learning.

Learners from different cultures use strategies in different ways, as a research tradition led by Rebecca Oxford has demonstrated. Related to this are differences in strategy use between male and female learners. Numerous studies have shown that female learners typically use strategies more widely and intensively than males, which may be related to the statistical advantage which female learners enjoy in language learning.

Affective factors

Affective factors relate to the learner's emotional state and attitude toward the target language. Research on affect in language learning is still strongly influenced by Bloom's taxonomy, which describes the affective levels of receiving, responding, valuing, organization, and self-characterization through one's value system. It has also been informed in recent years by research in neurobiology and neurolinguistics.

Anxiety

Although some continue to propose that a low level of anxiety may be helpful, studies have almost unanimously shown that anxiety damages students' prospects for successful learning. Anxiety is often related to a sense of threat to the learner's ego in the learning situation, for example if a learner fears being ridiculed for a mistake.

Socio-cultural factors

An important research tradition in SLA has investigated language learning as a form of language socialization. From this perspective, the acquisition of linguistic features is a process of taking on the habits and forms of a target culture. In other words, to acquire a language is to acquire a culture.

This research, informed by the work of social psychologists, has brought forward a number of important factors in language learning. In particular, it has pointed out the importance of attitudes toward the target language and its speakers. Students with negative attitudes toward the target language community, as well as students with negative attitudes toward their own first-language community, face particular difficulties in acquiring that language.

Motivation

The role of motivation in SLA has been the subject of extensive scholarship. This field is closely influenced by work in motivational psychology. Motivation is internally complex, and Dörnyei (2001, p. 1) begins his work by stating that "strictly speaking, there is no such thing as motivation." There are many different kinds of motivation; these are often divided into types such as integrative or instrumental, intrinsic or extrinsic. Intrinsic motivation refers to the desire to do something on the basis of an internal reward. Most studies have shown it to be substantially more effective in long-term language learning than extrinsic motivation, which is driven by an external reward such as high grades or praise. Integrative and instrumental orientations refer to the degree that a language is learned "for its own sake" (integratively) or for instrumental purposes. Studies have not consistently shown either form of motivation to be more effective than the other, and the role of each is probably conditioned by various personality and cultural factors.

Research has shown that motivation correlates strongly with proficiency, indicating both that successful learners are motivated and that success improves motivation. Thus motivation is not fixed, but is strongly affected by feedback from the environment. Accordingly, the study of motivation in SLA has also examined many of the external factors discussed above, such as the effect of instructional techniques on motivation. An accessible summary of this research can be found in Dörnyei (2001).

Understanding SLA

The systematic modelling of SLA is concerned with the question: What are the most important overall factors in language acquisition? Models of SLA have played an important role in laying out directions for future research, and also for informing practice in language teaching.

Different models of SLA have focused on different aspects of SLA and general linguistic research. For example, Schumann's Acculturation Model, which viewed second language acquisition as just one part of adapting to a new culture, emphasized findings related to language socialization. Krashen's Monitor Model prioritized research on input and affective factors. Long's Interaction Hypothesis took a social constructivist view of research on input. No single model of SLA has gained wide acceptance. Given that the field is complex and interdisciplinary, few scholars expect that any model will do so in the foreseeable future.

Concepts of ability

Numerous notions have been used to describe learners' ability in the target language. The first such influential concept was the competence-performance distinction introduced by Chomsky. This distinguishes competence, a person's idealized knowledge of language rules, from performance, the imperfect realization of these rules. Thus, a person may be interrupted and not finish a sentence, but still know how to make a complete sentence. Although this distinction has become fundamental to most work in linguistics today, it has not proven adequate by itself to describe the complex nature of learners' developing ability.

The notion of communicative competence was first raised by Dell Hymes in 1967, reacting against the perceived inadequacy of Chomsky's distinction between linguistic competence, and has proven extremely popular in SLA research. It broadens the notion of the kind of rules that competence can include. Whereas Chomsky treated competence as primarily grammatical, communicative competence embraces all of the forms of knowledge that learners must have in order to communicate effectively.

A closely related concept is proficiency. Proficiency is usually distinguished from competence, which refers to knowledge: "proficiency refers to the learner's ability to use this knowledge in different tasks" (Ellis, 1994, p. 720). Because any test of competence is a task of some sort, it may be argued that all measures of competence are in effect measuring some form of proficiency.

Both proficiency and competence are internally complex; they do not reflect a single attribute, but many different forms of knowledge in complex interrelationship. Research, such as much of that discussed here, requires some unitary concept of ability, but it has been clearly shown that different aspects of language ability progress at vary different rates. For example, Kasper and Rose (2002) review numerous studies of the complex relationship between grammatical and pragmatic proficiency. The measurement of language ability, although necessary for both research and teaching, is inevitably problematic.

References and further reading

Brown, H.D. (2000). Principles of language learning and teaching. (4th Ed.) Longman. ISBN 0-13-017816-0

Corder, S.P. (1967). The significance of learner's errors. International review of applied linguistics 5(4), 162-170.

Dörnyei, Z. (2001). Motivational strategies in the language classroom. Cambridge: Cambridge University Press. ISBN 0-521-79377-7

Ellis, R. (1994). The study of second language acquisition. Oxford: Oxford University Press. ISBN 0-19-437189-1

Kasper, G. & Rose, K.R. (2002). Pragmatic development in a second language. Oxford: Blackwell. ISBN 0-631-23430-6

Nation, I.S.P. (2001). Learning vocabulary in another language. Oxford: Oxford University Press. ISBN 0-521-80498-1

See also

• Education