That is, Freakonomics applied to tattoos: “…One possibility is that people just enjoy them for their intrinsic beauty, just as they might enjoy a work of art in a museum. The frequency with which people get tattoos in places they can’t easily see (in particular the lower back), makes me think this isn’t the primary answer. Rather, it would seem that the irreversibility of tattoos must be at the heart of their popularity. The fact that tattoos are (essentially) permanent makes them very powerful signaling devices: the more costly it is to take an action, the more powerful the signal that action carries. If I get tattoos on my face that look like the ones that Mike Tyson has, it sends a strong message to society about me…” Here.