Why do people wear Rolex watches or drive Bentleys, when less expensive goods can perform better? Why does anyone fight the crowds at the Louvre to see the "Mona Lisa" for 30 seconds, when they could view it online for hours? Well, they may be engaging in "costly signaling," in which people display their wealth to seem desirable, even if it costs money to show they have money. And it's not only people who use costly signaling: Male peacocks grow longer tails to be more attractive to females, at the cost of being easier to catch by predators.