Macaque apes turn out to be like humans:
Platt found that male macaques strongly preferred to look at pictures of females' rear ends and dominant males' faces. They liked them enough to pay, by sacrificing a chance to get a treat. But you had to bribe those same monkeys with treats to persuade them to look at female macaque faces or the faces of subordinate males.
This article available online at:
http://www.theatlantic.com/daily-dish/archive/2007/12/the-neurology-of-porn/223066/
