Yep, once the monkeys realized that they could see themselves, their first thought was "I wonder what my taint looks like." This proved that the rhesus macaques have a concept of self, like humans, and that they are major pervs, also like humans.
In a different study in the growing field of monkey boners, a group of researchers at the Duke University Medical Center took photos of female macaques' behinds and loaded them on a computer (it's unclear why they couldn't just type "monkey butts" on Google like the rest of us). The researchers then showed the pictures to male rhesus macaques and rewarded them with juice every time their eyes moved from picture to picture.
To set the mood, the headphones are playing Yello's "Oh Yeah" on repeat.
However, they found that male monkeys were willing to give up juice to continue looking at compromising photographs of females. Not just any females, but high-ranking ones -- essentially, they were paying to look at top-quality porn, because even monkeys know that you can get the amateur stuff anywhere for free. On the other hand, when the researchers put low-ranking females on the screen, they had to give the macaques extra juice to make them watch. They had to pay monkeys to look at ugly butts.
So what does this prove? For starters, that monkeys discriminate against each other based on their social status, just like us. The low-ranking females weren't necessarily "uglier" than the high-ranking ones; they were just more submissive. The other thing this proves is that monkeys will give up material goods to get momentary satisfaction, which leads us to the fact that ...