Editing Second-language acquisition (section)

== Learner language ==
{{Main|Interlanguage}}
Originally, attempts to describe learner language were based on [[Contrastive analysis|comparing different languages]] or [[Error analysis (linguistics)|analyzing learners' errors]].{{sfn|Ellis|Barkhuizen|2005|p=4}} However, these approaches could not fully predict all the errors learners make during the process of acquiring a second language. To address this limitation and explain learners’ systematic errors, the concept of [[interlanguage]] was introduced.{{sfn|Selinker|1972}} Interlanguage refers to the linguistic system that emerges in the minds of second language learners. It is not considered a defective version of the target language riddled with random errors, nor is it purely a result of errors transferred from the learner’s first language. Instead, it is viewed as a language in its own right, with its own systematic rules.{{sfn|Gass|Selinker|2008|p=14}} Most aspects of language—[[syntax]], [[phonology]], [[lexicon]], and [[pragmatics]]—can be analyzed from the perspective of interlanguage. For more detailed information, please refer to the main articles on [[Interlanguage]].

=== {{anchor|Order of acquisition}} Sequences in the acquisition of English inflectional morphology ===
{{Main|Order of acquisition}}

In the 1970s, several studies investigated the order in which learners acquired different grammatical structures.<ref group="note">These studies were based on work by {{Harvtxt|Brown|1973}} on child first-language acquisition. The first such studies on child second-language acquisition were carried out by {{Harvs|txt|last=Dulay|last2=Burt|year=1973|year2=1974a|year3=1974b|year4=1975}}. {{Harvtxt|Bailey|Madden|Krashen|1974}} investigated the order of acquisition among adult second-language learners. See {{Harvtxt|Krashen|1977}} for a review of these studies.</ref>  These studies showed that there was little change in this order among learners with different first languages. Furthermore, it showed that the order was the same for adults and children and that it did not even change if the learner had language lessons. This supported the idea that there were factors other than language transfer involved in learning second languages and was a strong confirmation of the concept of interlanguage.
{| style="width: 30%; float: right; border: 1px solid #BBB; margin: 1em" cellspacing=3 padding=10
|-
| 1.
| Plural ''-s''
| ''Girls go''.
|-
| 2.
| Progressive ''-ing''
| ''Girls going''.
|-
| 3.
| Copula forms of ''be''
| ''Girls are here''.
|-
| 4.
| Auxiliary forms of ''be''
| ''Girls are going''.
|-
| 5.
| Definite and indefinite <br />articles ''the'' and ''a''
| ''The girls go''.
|-
| 6.
| Irregular past tense
| ''The girls went''.
|-
| 7.
| Third person ''-s''
| ''The girl goes''.
|-
| 8.
| Possessive '''s''
| ''The girl's book''.
|-
| colspan="3" | <small>A typical order of acquisition for English, according to Vivian Cook's 2008 book ''Second Language Learning and Language Teaching''.</small>{{sfn|Cook|2008|pp=26–27}}
|}However, the studies did not find that the orders were the same. Although there were remarkable similarities in the order in which all learners learned second-language grammar, there were still some differences between individuals and learners with different first languages. It is also difficult to tell when exactly a grammatical structure has been learned, as learners may use structures correctly in some situations but not in others. Thus it is more accurate to speak of ''sequences'' of acquisition, in which specific grammatical features in a language are acquired before or after certain others but the overall order of acquisition is less rigid.  

Recent studies have shown that universality and individuality coexist in the order of grammatical item acquisition.<ref>{{Cite journal |last1=Murakami |first1=Akira |last2=Alexopoulou |first2=Theodora |date=September 2016 |title=L1 INFLUENCE ON THE ACQUISITION ORDER OF ENGLISH GRAMMATICAL MORPHEMES: A Learner Corpus Study |url=https://www.cambridge.org/core/journals/studies-in-second-language-acquisition/article/l1-influence-on-the-acquisition-order-of-english-grammatical-morphemes/3263C3E82ECA4A7EB19D8F50E45FA1C3 |journal=Studies in Second Language Acquisition |language=en |volume=38 |issue=3 |pages=365–401 |doi=10.1017/S0272263115000352 |issn=0272-2631}}</ref> For example, items such as articles, tense, and the progressive aspect are particularly challenging for learners whose native languages, like Japanese and Korean, do not explicitly express these features. On the other hand, items like the third-person singular -s tend to be less influenced by the learner's native language. In contrast, articles and the progressive -ing have been confirmed to be strongly affected by the learners' native language. For more detailed information, please refer to the main articles on [[Order of acquisition]].

=== Learnability and teachability ===
Learnability has emerged as a theory explaining developmental sequences that crucially depend on learning principles, which are viewed as fundamental mechanisms of interlanguage language acquisition within learnability theory.<ref>{{Cite web|url=https://scholarspace.manoa.hawaii.edu/bitstream/10125/38613/1/Parker%20%281989%29_WP8%281%29.pdf|title=Learnability Theory and the Acquisition of Syntax|last=Parker|first=Kate|date=May 1989|website=University of Hawai'i Working Papers in ESL, Vol. 8, No. 1, pp. 49-78.}}</ref> Some examples of learning principles include the uniqueness principle and the subset principle. The uniqueness principle refers to learners' preference for a one-to-one mapping between form and meaning, while the subset principle posits that learners are conservative in that they begin with the narrowest hypothesis space that is compatible with available data. Both of these principles have been used to explain children's ability to evaluate grammaticality despite the lack of explicit negative evidence. They have also been used to explain errors in SLA, as the creation of supersets could signal over-generalization, causing acceptance or production of ungrammatical sentences.<ref name=":3">{{Cite web |last=Yip |first=Virginia |date=Aug 1990 |title=Interlanguage Ergative Constructions and Learnability |url=https://files.eric.ed.gov/fulltext/ED335903.pdf |website=CUHK Papers in Linguistics, No. 2. p45-68}}</ref>

Pienemann's [[Teachability Hypothesis|teachability hypothesis]] is based on the idea that there is a hierarchy of stages of acquisition and instruction in SLA should be compatible with learners' current acquisitional status.<ref>{{Cite journal|last=Pienemann|first=Manfred|date=1989|title=Is Language Teachable? Psycholinguistic Experiments and Hypotheses|url=https://eric.ed.gov/?id=EJ385570|journal=Applied Linguistics|language=en|volume=10|issue=1|pages=52–79|doi=10.1093/applin/10.1.52|url-access=subscription}}</ref> Recognizing learners' developmental stages is important as it enables teachers to predict and classify learning errors. This hypothesis predicts that L2 acquisition can only be promoted when learners are ready to acquire given items in a natural context. One goal of learnability theory is to figure out which linguistic phenomena are susceptible to fossilization, wherein some L2 learners continue to make errors despite the presence of relevant input.

=== Variability ===

Although second-language acquisition proceeds in discrete sequences, it does not progress from one step of a sequence to the next in an orderly fashion. There can be considerable variability in features of learners' interlanguage while progressing from one stage to the next.{{sfn|Ellis|1997|pp=25–29}} For example, in one study by [[Rod Ellis]], a learner used both "No look my card" and "Don't look my card" while playing a game of bingo.{{sfn|VanPatten|Benati|2010|p=166}} A small fraction of variation in interlanguage is ''free variation'', when the learner uses two forms interchangeably. However, most variation is ''systemic variation'', a variation that depends on the [[context (language use)|context]] of utterances the learner makes.{{sfn|Ellis|1997|pp=25–29}} Forms can vary depending on the linguistic context, such as whether the subject of a sentence is a pronoun or a noun; they can vary depending on social contexts, such as using formal expressions with superiors and informal expressions with friends; and also, they can vary depending on the psycholinguistic context, or in other words, on whether learners have the chance to plan what they are going to say.{{sfn|Ellis|1997|pp=25–29}} The causes of variability are a matter of great debate among SLA researchers.{{sfn|VanPatten|Benati|2010|p=166}}