Caspar writes:

“I am a developmental psychologist specializing in infant cognition and once dated a auditory neuroscientist. We knew we would hit off when on our very first date we both agreed that the Necker cube, as well as being one of the most psychologically profound optical illusions there is, would make an excellent tattoo. So on our fourth date, we went and got matching copies.You see it happening here: www.loadofold.com/ade/necker1.html

We didn’t stay together very much longer but both still love our tattoos. Especially, showing them off at conferences.