Editor's Note: This story was updated at 3:30 p.m. E.T.
"Hey, no fair!"
Anyone who's spent more than 5 minutes on a playground is likely to hear that phrase at least a few times.
But it turns out that although kids across the world develop a sense of when they, themselves, have been wronged by a very young age, their tendency to recognize unfairness when others are wronged varies across cultures, new research suggests.
Across cultures, children develop a dislike of receiving less than others by age 10, but it isn't until later that they begin to feel discomfort when others get the short end of the deal, the new research found. In the study of kids ages 4 to 15 from seven countries, children in just three countries showed any sign of caring about fairness for other kids.
"A negative reaction to getting less than others may be a human universal," said study co-author Katherine McAuliffe, a psychologist at Yale University. By contrast, "A negative reaction to getting more than others may be importantly influenced by culture." [5 Ways to Foster Self-Compassion in Your Child]
There's no doubt that fairness looms large in the imagination and concerns of children. From a young age, children have a sense of morality, and will punish nasty puppets that have stolen tasty candy from another child, a study published this year in Current Biology revealed. And tots' desire for justice starts when they're as young as 8 months, a 2011 study in the journal Proceedings of the National Academy of Sciences found. Moreover, past research in the United States showed that children would rather toss a perfectly good piece of candy in the trash than see the candies divvied up unfairly, one researcher previously told Live Science.
The sense of what's fair also changes as people age; older kids are more willing than younger ones to consider merit when looking at how resources are divvied up, a 2010 study found. And even chimps have a sense of fairness, according to research published in 2013 in the journal Proceedings of the National Academy of Sciences.
But McAuliffe and her colleagues wondered how fairness developed across cultures.
To answer that question, the team studied 866 pairs of children, ages 4 to 15, from seven different countries: Canada, India, Mexico, Peru, Senegal, Uganda and the United States. In their setup, they put a pair of children together and had one (the "actor") pull a lever to dispense candy. Half the time, the dispenser gave them a fair split of candy. But the other half of the time, the actor got either more or less than his or her partner. At that point, the lever puller (whose sense of fairness was being tested) could either reject the allocation — denying everyone the candy — or take it.
In all the countries, kids tended to reject a setup where they got less candy than their partners, typically by age 4 to 6 in the United States and by as late as age 10 in Mexico. (All the kids in the Mexican cohort were from small villages and all knew each other, which could have somehow influenced the results, the researchers said.)
But kids had to be much older to reject setups where the lever puller got four pieces of candy and his or her partner got just one.
Moreover, only kids from certain countries rejected this setup. Only American, Canadian and Ugandan children seemed to develop an aversion to their partner getting less than them. The kids who rejected candy allocations that shortchanged partners were pre-adolescents, the researchers reported today (Nov. 18) in the journal Nature.
The finding suggests that the drive to be treated fairly is a basic human response, McAuliffe said. By contrast, equality for others may not be nearly so innate.
"Equality norms are often emphasized for children in Western cultures," McAuliffe said, which may explain why children learn those rules later on in childhood only in Western countries.
(It's possible that Ugandan society also emphasizes these norms. But there is also a huge number of American teachers in Uganda, so perhaps these Westerners are teaching a Western sense of equality to the children in East Africa, the researchers speculated.)
The findings provide a great cross-cultural comparison, and are consistent with those from other studies, which have found people have a "self-serving bias," Keith Jensen, a psychologist at the University of Manchester in England, who was not involved in the study, told LIve Science in an email.
Still, a general concern for the welfare of others is still likely a cultural universal, just one that has a steeper learning curve, he added.
"Children learn the rules of their societies and internalize the norms," Jensen said. "Some norms are easier to learn than others. Learning to be selfish is easier to learn than selflessness."
There are other limitations to the study. For instance, the team doesn't know enough about the cultures in other places to speculate about what aspects of culture are at play, or whether the attitudes of the children reflect the overall inequality that prevails in a country, said study co-author Peter Blake, a psychologist at Boston University in Massachusetts.
Jensen agreed. "The choice of cultures to study was a bit of a smorgasbord, so it’s not possible to make broader claims on the ecological or economic factors that might lead to these results," he said.
For some of the countries, they do have one interesting data point — the Gini coefficient, which is a rough measure of a country's income inequality and could shed light on how kids perceive inequality. However, the variation in each child's microenvironment — whether he or she lives in a village with 500 people who have no access to television or in a bustling metropolis where the wealthy rub shoulders with the have-nots — makes it hard to say how the country's overall income equality would actually affect a child's experience of equality, he added.
"You would need to go much more local to determine what the experience of inequality is," Blake said. "There are no good measures for what children's inexperience of inequality is."
Editor's Note: This story was updated to include additional comment by Keith Jensen.
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Tia is the managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.