Editing Second-language acquisition (section)

=== 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}}