According to accommodation theory, there are two main strategies: convergence and divergence. Convergence occurs when the speaker adjusts her normal speech to make it more similar to the speaker’s speech or when the speaker converges toward a prestigious norm that he believes is favored by the speaker. In short, the speaker accepts the values of the interlocutor and seeks to demonstrate that acceptance with her own linguistic behavior.
Rather, divergence occurs when speakers seek to alter their discourse in order to make themselves linguistically different. Both convergence and divergence can take place up or down. Upward convergence occurs when speakers adjust their speech to exhibit the norms of high-status individuals in their society. Downward convergence involves adjustments in the direction of speech norms from a higher class to a lower class.
For example, a person with a Ph.D. in physics will speak differently when explaining quantum mechanics to a high school dropout than when discussing physics with colleagues; that is, the physicist will use language in a way designed to simplify complex concepts for his less educated interlocutor. Generally, upward convergence is the most common type because it is based on the universal desire for approval from those we respect and emulate.
Upward divergence occurs when speakers emphasize standard features of their speech, while downward divergence occurs when speakers emphasize nonstandard features of their speech. An example of upward divergence would be two people from different classes arguing, with the individual from a higher socioeconomic background emphasizing standard features of his speech to distinguish himself from the lower class interlocutor. In the same example, the person of lower socioeconomic status emphasizing their less standard way of speaking would be exhibiting downward divergence.
The causes of convergence and divergence can be complicated. One of the best known studies on the theory of accommodation was started by Giles and his colleagues. It concerned conversations between nurses of unequal rank and how convergence and divergence operated based on their ability to use the English language. The results showed that when talking to lower-ranking nurses, those with higher status used less standard English; likewise, when lower-ranking nurses spoke to their higher-ranking colleagues, they spoke more standard English.
Also, people are more likely to convert their speaking rates in a way that emphasizes the stereotype of their interlocutors’ speaking rates and their way of using language. Also, speakers tend to move from convergence to divergence by reassessing the person they are talking to during the conversation.