I spent 2 winters in Antarctica with people with strong accents, e.g. Scottish, Welsh, Northern Irish, Scouse, Geordie, Cumbrian, and Devonian. On my return to the UK a lot of people said I'd developed a Brummie accent, although none of my fellow winterers were from Birmingham. My theory was that I'd developed an accent averaged across all the strong ones! It's interesting to see a scientific study showing how accents changed over an Antarctic winter!