What causes some people to unconsciously imitate the accents of others? Background: I often notice that when I talk with someone with an accent that I often unconsciously start to imitate their accent. Similarly, you see some people that very quickly after moving to a country start to adopt the local accent whereas others maintain their original accent for many years.

Questions


What causes individual differences in the tendency to unconsciously take on accents?
Has there been research on the process of unconsciously imitating accents?
TLDR When two speakers become more similar in their speech this is called convergence or accomodation (opposite: divergence). This can occur on all levels of language, phonetics and phonology, syntax, semantics, and pragmatics. When mutual intellgibility is not an issue, accomodation mainly occurs when speakers like each other or want to appear likeable.


  Q: Has there been research on the process of unconsciously imitating accents?


Phonetic accommodation has been documented for a range of cases, for example for 


mean intensity (Natale 1975)
perceptual similarity of individual lexical items (Pardo 2006)
vowel duration (Kim 2012, Pardo 2012)
voice onset time, fundamental frequency and the frequency of the first formant in vowels (Kim 2012)


Most studies have not studied spontaneous interaction and were mostly based on special elicitation techniques, but accommodation has also been documented in spontaneous speech (Levitan et al. 2012).


  Q: What causes individual differences in the tendency to unconsciously take on accents?


We converge with interlocutors that we like or that we want to like us (shown by, for example, Babel 2009). We diverge from those that we don't like, although this may be rarer - In general, speakers adopt pronunciations that they think are socially desirable in a situation (see Mather 2012 and the classic study by William Labov it is based on).

I beg to disagree with @Skippy's opinion that people "without a firm sense of identity or an underdeveloped ego" are more likely to accomodate or converge with another speaker. It rather appears that converging with an interlocutor is a social skill connected to empathy. You speak more like your interlocutor or a group you interact with so that you will be accepted as one of the team. This will make social interaction and achieving your aims easier than if you did not accomodate.

I don't mean to say that there are not people with "a firm sense of identity" that are particularly unlikely to converge with other speakers. But I do disagree with the implication behind these phrases, namely that "a firm sense of identity" (and not accomodating) is something desirable and an "underdeveloped ego" (and accomodating) something undesirable. On the contrary, converging with other speakers is an important and valuable social skill that helps us connect with other people and establish common ground. Those who (even unconsciously) insist on not accomodating to other speakers could also be characterised as having problems in adapting to new people or groups they come in contact with and lacking in empathy. 

But I do see the point that those who are desparate for the approval of other people might go to great lengths to get it - including accomdating their speech to a high degree.