I’m a little embarrassed to admit that I used to bite my nails. According to Tom Stafford, who still bites his, Gordon Brown, Jackie Onassis, and Britney Spears are or were nail biters, too. He cites papers that suggest 45% of teens bite their nails and you can imagine that some of them would continue to do so as adults. He did a bit of research on the act of nail biting which doesn’t have underlying psychological causes:
First off, there is the fact that putting your fingers in your mouth is an easy thing to do. It is one of the basic functions for feeding and grooming, and so it is controlled by some pretty fundamental brain circuitry, meaning it can quickly develop into an automatic reaction. Added to this, there is a ‘tidying up’ element to nail biting – keeping them short – which means in the short term at least it can be pleasurable, even if the bigger picture is that you end up tearing your fingers to shreds. This reward element, combined with the ease with which the behaviour can be carried out, means that it is easy for a habit to develop…
I don’t even know what got me to stop biting my nails other than, one day, deciding I didn’t want to do it anymore.