Code-switching relates to, and sometimes indexes social-group membership in bilingual and multilingual communities. Some sociolinguists describe the relationships between code-switching behaviours and class, ethnicity, and other social positions. In addition, scholars in interactional linguistics and conversation analysis have studied code-switching as a means of structuring talk in interaction. Analyst Peter Auer suggests that code-switching does not simply reflect social situations, but that it is a means to create social situations.
Markedness Model
The Markedness Model, developed by Carol Myers-Scotton, is one of the more complete theories of code-switching motivations. It posits that language users are rational, and choose (speak) a language that clearly marks their rights and obligations, relative to other speakers, in the conversation and its setting. When there is no clear, unmarked language choice, speakers practice code-switching to explore possible language choices. Many sociolinguists, however, object to the Markedness Model’s postulation that language-choice is entirely rational.
Communication Accommodation Theory
The Communication Accommodation Theory (CAT), developed by Howard Giles, professor of communication at the University of California, Santa Barbara, seeks to explain the cognitive reasons for code-switching, and other changes in speech, as a person seeks either to emphasize or to minimize the social differences between him- or herself and the other person(s) in conversation. Prof. Giles posits that when speakers seek approval in a social situation they are likely to converge their speech with that of the other person speaking. This can include, but is not limited to, the language of choice, accent, dialect, and para-linguistic features used in the conversation. In contrast to convergence, speakers might also engage in divergent speech, with which an individual person emphasizes the social distance between him- or herself and other speakers by using speech with linguistic features characteristic of his or her own group.
Code-switching and Diglossia
In a diglossic situation, some topics and situations are better suited to one language over another. Joshua Fishman proposes a domain-specific code-switching model (later refined by Blom and Gumperz) wherein bilingual speakers choose which code to speak depending on where they are and what they are discussing. For example, a child who is a bilingual Spanish-English speaker might speak Spanish at home and English in class, but Spanish at recess.