As a linguist, I was fascinated by this posting. I am familiar with the concept, but did not know the term used to describe our linguistic practice. I would like to come back to the topic in more depth in a future comment, but for now, will share two experiences that drew on precisely this notion.
The first incident occurred during a discussion I was having with my tutor group. I must have been in my mid-thirties at the time, and was talking with a multi-ethic group of adolescents in an inner-London comprehensive school. I had been their tutor since they arrived several years previously, had taken them away to our rural annex, so we knew each other well by this time. At some stage during the discussion, I referred to a ‘Merc’ car. Suddenly, the group collapsed in laughter and mimicked the word, to my acute embarrassment. I realised that I had unwittingly infringed their image of me, a teacher, by using a word from a register of language which they did not associate with my role. I had often spoken with them about appropriate use of language but here was I learning a sharp lesson from my pupils.
The second incident happened a few years later when I was a Deputy Headteacher and conducting a school assembly. In an effort to reinforce the message about where and when to use different forms of language, my co-deputy and I enacted a scene. We came on stage, dressed casually, cigarette in hand. The conversation began something like this:
Ciaio, Babe. Just had a …ing awful class with 7J, little b…s You get the drift. After an almost imperceptible pause, the assembled pupils fell into laughter. Unlike the first incident, they were not laughing AT us but WITH us. The difference lay in the intentionality of our use of language, but revolved around the same notion: when register is or is not appropriate. Needless to say, I went on to talk about this in more explicit terms. I hope it was a lesson those...