This article was originally published in Futurity. 

People in the US cherish their ideals of fairness. And American children can be especially strident—some might say loud—advocates for equality. Anyone who has ever cut and distributed a child’s birthday cake knows how closely those little eyes watch for injustice. And when they see it, especially in their ever-so-slightly-smaller slice, they protest with the anguished cry: “No fair!”

How does this sense of fairness emerge in children? Is it innate or learned? And does it vary across cultures, or do US values represent the norm? Peter Blake, an assistant professor in Boston University’s department of psychological and brain sciences and director of the Social Development and Learning Lab, has spent a decade studying these questions.

His latest research, a collaboration with psychology professor Katherine McAuliffe, tested an unprecedented 866 pairs of children across seven diverse societies to examine how ideas of fairness emerge, finding surprising similarities among children in Canada, the United States, and Uganda. The research appears in Nature.

Human norms of fairness, cooperation, and altruism have puzzled scientists since Darwin’s day and remain vital to our understanding of human evolution. “If you really want to understand humans, you need to understand cooperation,” says Felix Warneken, an associate professor of psychology at Harvard and coauthor of the paper. “We can’t survive on our individual abilities; so much of what we do depends on cooperation.”

In their earlier research, Blake and McAuliffe, who will join the faculty of Boston College in January 2016, tried to establish when children acquire concepts of fairness. “It wasn’t obvious that we’re just born with a sense of fairness, but everyone seems to have one,” says Blake. “How do these different senses of fairness emerge? And do they have a common foundation or origin?”


To examine these questions, the scientists built a toy they call the “inequity apparatus,” or—less forbiddingly—the Skittle-ator.

It’s a two-foot-long wooden plank with two small, raised trays near the center. Two children sit on either side, facing each other, as the scientists place Skittles on the trays. In front of one child are two handles, one red and one green. If the child pulls the green handle, the trays tip toward each child and dump Skittles into bowls where they can keep them. But if the kid pulls the red handle, the Skittles slide into a bowl in the center, where neither child can keep them.

In general, when the scientists offer a young child, around age four or five, a “good deal”—she gets four Skittles and the other child gets one—she pulls the green handle and happily takes the four Skittles. But when the scientists offer a “bad deal”—she gets one and the other kid gets four—most kids pull the red handle and walk away empty-handed. It seems like pure spite—if you get more, I don’t want any—and the scientists say that’s part of it.

But there may be more going on: giving up one Skittle is a sacrifice, but it prevents another kid (“the competition”) from gaining a relative advantage. By pulling the red handle, a child also signals that she won’t be cheated or exploited, even for a tasty sugar hit. “Kids are willing to pay the price to prevent the bad deal,” says Blake. “And it just becomes stronger with age.”

But a funny thing happens around age eight—kids begin rejecting the “good deal,” too, refusing to take four Skittles when the other child gets only one. “At age eight, we saw this sudden shift,” says Blake. “And when we asked the children why, they would say, ‘It’s not fair.’” Not fair, that is, to the other kid.

To double-check these results, the scientists offered children equal allocations of Skittles—I get one, you get one—in what might be called “a good deal for everybody.” Children accepted this offer at all ages.

“It’s a really good test of a child’s sense of fairness,” says Warneken of the Skittle-ator. “The game tests not just what people say, but what they actually do.”

The study design builds on McAuliffe’s previous work with cotton-top tamarins. “Tests from animal studies are very intuitive—you can’t use language or written instructions with monkeys—so the tests also work well with children,” says McAuliffe. The tamarins, it turns out, gobbled Froot Loops at any opportunity, whether the handouts were fair or not. Human children were far more discerning.


These early studies got the scientists thinking. If this trait—refusing a deal that’s unfair to others—appears only around age eight, only in humans, and goes against economic models of rationality, something bigger than biology must be at work. “This seems like a behavior that is shaped by culture,” says Blake.

But the scientists had only tested children in the United States—actually, only in public parks in and around Boston. Would the results hold across cultures? It’s a question that many researchers are asking more often, especially after an influential 2010 paper in Behavioral and Brain Sciences noted that behavioral scientists conduct most of their research on subjects from Western, educated, industrialized, rich, and democratic (WEIRD) societies.

“Most of what we know about psychology comes from studying university undergrads in Western countries,” says McAuliffe. “But is the developmental trajectory in the United States the same across cultures? What is the true sense of human fairness?”


To test that question, the scientists teamed up with researchers who had ongoing projects in other countries, trained them on the inequity apparatus, and asked them to include the experiment in their repertoire. Over four years, the collaborators tested a total of 866 pairs of children in Canada, India, Mexico, Peru, Senegal, Uganda, and the United States. (While some scientists used different local candies or cookies in the test, others stuck with Skittles if they could find them in local stores. “Skittles have surprising penetration into the global market,” notes Blake.)

The scientists suspected that children from all cultures would reject the bad deal (I-get-one-you-get-four), and that turned out to be the case. However, children tested in Mexico rejected the bad deal at a much later age, around ten instead of four. Blake isn’t sure why this happened, but the Mexican children were from small villages and most knew each other, so he suspects that this personal dynamic might have reduced competition.


The big surprise came with the good deal. The scientists had speculated that children in Canada, like those in the United States, would reject the good deal around age eight, because of common cultural norms. But they weren’t sure how children in non-Western societies would react. “Will older kids reject that good deal everywhere? We predicted that no, that probably is not going to happen,” says Blake. “We found that it showed up in the US and Canada, but it also showed up in Uganda, which kind of threw us.”

Among all the countries tested, only Canada, the United States, and Uganda showed this common trend. The scientists have a few possible explanations for the surprising find. The area of Uganda tested is rural and agrarian—very different from urban United States and Canada—but many schools in the area show a heavy Western influence. Perhaps Western-trained teachers transmitted cultural norms of fairness to their students. Or, says Blake, children in other countries might see this type of fairness as a valuable trait, but one that applies only to adults.

“Or it’s possible that there’s a completely different reason,” says Blake. “Maybe kids in the US will reject the good deal for one reason, and in Uganda they do it for another. We don’t know.”

The study is “really just a first pass,” says McAuliffe, that opens up many questions and avenues for further research. The scientists want to go both broader, studying more societies, and deeper, learning more about each group’s culture. “Right now, we have a good measurement of behavior but no in-depth understanding of cultural patterns, socialization, or anthropology,” says Warneken. The scientists also note that they only tested children up to age 15 and want to test adults at various stages of life. Probably with a prize other than Skittles.

The work contributes to a larger area of research examining both the short- and long-term effects of scarcity and inequity on everything from IQ scores to self-confidence.

“We put kids in a situation where they’re either receiving less than a peer or more. That’s kind of what children are born into, right? They’re born into a circumstance where they have less or more than others,” says Blake. “There are bigger questions there, about when kids really become aware of this and whether it affects the rest of their lives.”

The Templeton Foundation funded the work.

Featured image courtesy of Pixabay.

About The Author

Avatar photo

Barbara Moran is an award-winning science journalist who has written for many publications, including the New York Times, New Scientist, Technology Review, the Boston Globe Magazine, and the Hartford Courant. She has also produced television documentaries for PBS, the Discovery Channel, the History Channel, and others. She has an MS in science journalism from Boston University, and was a 2001 Knight Fellow at MIT. Her first book, The Day We Lost the H-bomb, a narrative nonfiction account of the worst nuclear weapons accident in history, was an Amazon pick of the month when published in 2009, and was shortlisted for the History of Science Society’s Davis Award. Moran’s investigative work has been featured on NPR, CBC, BBC Online, and many other media outlets. In addition to writing for BU Research, she is an adjunct professor in BU's graduate program in science journalism.