Our ability to learn language never ceases to amaze me. We can not only communicate, we use language in amazingly subtle and nuanced ways. One of the clever things our brains are able to do is to tailor our language to the person we are speaking to. I’ve heard someone switching accents from sentence to sentence as she took part in a conversation involving people from her native country and her adopted one. When I write, I write differently for scientific articles, business emails, letters to friends and so on. I sometimes use particular slang and in-jokes with my friends that I don’t use with strangers.
This all seems to happen effortlessly and unconsciously, but it isn’t perfect. It sometimes breaks down. Language we use a lot in one situation can become such a habit that it bleeds over into other situations. Changes in language use that are conscious at first become automatic after a while. When I lived in England, I intentionally modified some of my strange New Zealand pronunciation and vocabulary so that people there could understand me better. (The way we say “ten” for example, is almost unintelligible to English people.) When I went back to New Zealand, I found some of these changes had stuck, and I couldn’t remember how to say some things in ‘New Zild’, while at other times some English-isms just slipped out by accident. This effect, where a conscious ‘accommodation’ of our language becomes a habit is a possible factor in language change. If people start to modify their language in some conscious way for whatever reason — be it playfulness, playing up to higher status people, purposefully exaggerating differences to reinforce their identity — this can become a habit and spread through all their language use, becoming their new ‘normal’ way to say something.
This kind of habit forming can also cause problems. In science (I suppose in any specialised job) we use a lot of jargon to make our communication more concise and precise. The problem is that we use the technical jargon so much, that for many scientists it becomes hard to describe their work without using these technical words. Sometimes the words we use in a technical way are quite common words which have quite different meanings in everyday life. This can lead to big misunderstandings about what a scientist really means when she or he is speaking to the public. One topical and unfortunate example is the way discussion about climate change can be heavily distorted simply by the words that are used. Callan Bentley has a table of such dangerous words in his blog, along with some less fraught alternatives.