Editor's summary in Nature of a recent paper by Fehr and colloborators Cooperation is child's play:
"The way that children interact in specially designed tests (well, games) can illuminate the mechanisms behind human altruism and cooperation. Fehr et al. present evidence that young children's other-regarding preferences (where 'Smarties, jellybabies and fizzers' are the rewards in a sharing game and an envy game) take a particular form — inequality aversion. This behaviour pattern develops between the ages of 3 and 8 years. Aged 3 or 4, most children behave selfishly, while by the age of 7 or 8 the vast majority prefer resource allocations that remove inequality. But if the removal of advantageous inequality involves costly sharing, the egalitarian allocation is chosen less often and children tend to favour members of their own social group. These findings suggest that egalitarianism and parochialism have deep developmental roots."
The summary has links to related papers which need subscription. Nature News also has a summary which does not need subscription Children learn rules of equality by age eight. Excerpts:
"Although this might seem an obvious finding, it's important to confirm anecdotal evidence with experiments, says Matthias Sutter of the University of Innsbruck in Austria, who studies fairness and trust behaviour in children. "Having children myself, I can confirm [that 3-year-olds are selfish]," he says. "But we don't know when the change happens, or the magnitude of the change."
Several other factors influenced how egalitarian the children were. The team found that children without siblings were 28% more likely to share than children with siblings. On the other hand, the youngest children in a family were 17% less willing to share than children who had only younger siblings. Sutter, who is one of five children, thinks these results make sense: "You have to take care that you get some of the pie," he says. "If you're an only child, there's no need for that."
In addition, if children knew that their partner was from the same playgroup or school (an 'ingroup' member), they were more concerned about being fair, and with age this bias increased. This suggests that being nice to people you know – parochialism – is something that develops alongside a sense of equality, says Fehr.
Chimps versus children
The findings are also interesting from an evolutionary perspective, the team suggests. Similar experiments performed on chimpanzees show that the animals aren't willing to provide food for a partner even if it doesn't affect the food they receive2. "Chimps seem not to care about the other's welfare in this game, whereas children at age eight already care a lot, but children at age three care only a little," Fehr says.
Further work along these lines could reveal more about why humans are so bothered about fairness, and the part this has played in building human societies. Without it, says Sutter, "there would be no education, no socialization, no social norms"".