A range of studies in different contexts have confirmed that the linguistic environment in
which one lives, including the languages and varieties one is exposed to has a significant
effect on the acquisition of an L2. The key factors appear to be the degree to which learners
are afforded exposure to input in the target language (Krashen, 1985; Ortega, 2009;
VanPatten, 2004), and the opportunities they have to interact with ‘native speakers’ or
advanced users of the language. 
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Exposure to speakers of the target language has consistently been found to aid acquisition.
In the context of French immersion education in Canada, for example, Rehner et al. (2003)
found that learners do not acquire vernacular variants of French L2 unless they have contact
with French L1 speakers outside of the classroom. Many studies of the effect of exposure to
L2 speakers have been done in the context of ‘study-abroad’ programmes. In a comparison
of study abroad and at-home L2 learners from the US, for example, Collentine (2004) found
that while at-home students developed more discrete grammatical and lexical features than
did the study abroad students, the study abroad students developed better oral narrative
ability and produced more semantically dense language. Similarly, Segalowitz and Freed
(2004) found that studying abroad produced significant positive effects on learners’ oral
fluency and overall proficiency.
In bilingual societies in which the L2 is one of the main languages spoken, the social
contexts in which it tends to be spoken can affect learners’ linguistic use, choice, and
development (Tarone, 2007). In diglossic societies (Ferguson, 1959), for example, in which
different languages are confined to separate, well defined domains (such as academic and
social), learners may be more likely to master different sets of pragmatic functions and lexical
items for different languages. Even in non-diglossic societies, L2 learners are likely to
produce a significantly more fluent and accurate language in some social contexts than in
others (Selinker & Douglas, 1985). Work by Tarone and Swain (1995) in French immersion
settings, for example, found that students used English outside of class not because their
French was not good enough but because the French they had learned in the classroom was
deemed too formal, and they lacked a vernacular French more appropriate for adolescent
social interaction.