Something to do with evolution and genetic diversity in the face of risky environments – expanding the gene pool for stronger offspring (but of course the vikings knew that when they went off to do a bit of pillaging).
It’s also been found that men flinch less when subjected to sudden bursts of noise when looking at someone they are attracted to. A good reason to have attractive dental nurses I would have thought.
Updated 1 October 2010: Researchers at Keele University who discovered that people could cope for longer with pain when they were swearing (as opposed to using neutral words) have been awarded the Ig Nobel prize by Harvard University. These awards recognise research that makes you laugh – then think, so not completely bad science.
Perhaps on that basis Gordon Ramsay, who had been recorded at 3 swear words a minute over a 100 minutes, should be totally pain free?