I am interested in reasons why people engage in body modifications, such as piercings or tattoos. I am aware of some religious reasons, and some religions forbidding such activity, but I am interested in personal reasons in particular.

For example, I don't see how piercings and tattoos communicate fitness or fertility, help with symmetry, or improve sexual attractiveness. Perhaps there are other emotional or linguistic meanings involved?

Is there research into why people use piercings or tattoos for personal reasons?