Your accountant (probably) doesn’t have a tattoo. This isn’t because they’re scared of needles or because they’re uncool losers. It’s because tattoos are essentially costly signals that change the perception of others. These costly signals have been proven to increase sales of MP3 players, to boost blood donations, and to get diners to pay more for their meal. Hear how on today’s episode with world-renowned behavioural scientist Uri Gneezy.