Some white-faced capuchin monkeys stick their fingers deep into the eye sockets of their friends, and others will use an ally's body parts to whack a common enemy. A new study found that older, sociable capuchins are prone to inventing more new types of social behaviors, many of which seem to function as tests of friendship or displays against enemies. However, younger monkeys are more innovative with their behavior in different categories - for example, ways to interact with the physical environment, such a flipping over cow pies to use as see-saws. Some white-faced capuchin monkeys stick their fingers deep into the eye sockets of their friends. A new study found that older, sociable capuchins are prone to inventing more new types of social behaviors, many of which seem to function as tests of friendship or displays against enemies.