Yesterday, I wrote about selfless capuchin monkeys, who find personal reward in the act of giving other monkeys. The results seemed to demonstrate that monkeys are sensitive to the welfare of their peers, and will make choices that benefit others without any material gain for themselves. Today, another study looks at the same processes in a very different sort of cheeky monkey – human children.

Humans are notable among other animals for our vast capacity for cooperation and empathy. Our concern about the experiences of other people, and our natural aversion to unfair play are the bedrocks on which our societies and moral codes are built. But are we born with this penchant for equality or does it