MIT Study of Tsimané People Shows How to Trick Kids Into Giving You Cookies

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How does a child's sense of fairness develop? An MIT study shows it's numbre sense and not necessarily age. Image: Flickr/Michael Coghlan cc license.
How does a child’s sense of fairness develop? An MIT study shows it’s numbre sense and not necessarily age. Image: Blogtrepreneur under cc license.

Imagine the injustice: your child, perhaps aided and abetted by your significant other, baked cookies, and now, because they did the baking, they feel entitled to the lion’s share of the cookies. You, on the other hand, know that, regardless of who did the baking, the only fair distribution is an even one: you should split the cookies three ways (or two, or four, or nine, or whatever is the cookie-eating population of your close family).

MIT researchers worked with the Tsimané People near San Borja, Bolivia to discover how to keep your family’s overdeveloped sense of moral justice from interfering with your dessert: having an equal distribution of rewards despite an unequal investment of work depends on keeping your kids from learning to count.

The study speaks to a longstanding question in child development: younger kids gravitate toward an egalitarian model of fairness–your two-year-old would split the cookies evenly (though if your two-year-old is anything like mine were, I would first evaluate whether the cookies contain “secret ingredients”). But, as kids get older, they switch to a merit-based opinion of fairness–if your 12-year-old baked the cookies while you, say, snuck into his bedroom to read his comic books, you would be lucky to get even a fraction of what he kept for himself.

The question is, what is it about child development that turns an equitable two-year-old into a selfish, hoarding 12-year-old? Is it a natural process of aging? Is it socialization? Is it… something else? To answer the question, the researchers took advantage of an important fact of Tsimané culture: in this society, children learn to count at very different ages.

The researchers gathered 70 children ranging in age from three to 12 and assessed their years in school and their counting ability. Then they explained the following scenario: “One day, two children had been sent to pick bananas. The first child worked very hard and brought back many bananas. The second child did not work very hard and only brought back a few bananas.” The experimenter represented this by putting 18 banana cutouts next to the hard-working child and 4 banana cutouts next to the lazy child. Now the kids were given cookie cutouts and asked to distribute them as rewards “fairly” between these kids.

Sure, more older kids chose a merit-based distribution, giving more cookies to the hard-working kid. But it wasn’t clean–there were older kids who were egalitarians and younger kids who were steely-eyed little cookie hoarders. Much cleaner was whether or not they could count–an egalitarian versus merit-based opinion of fairness depended on a child’s concept of numbers. Fifty-seven percent of kids who couldn’t count split the cookies evenly; 74 percent of kids who could count gave more cookies to the hard-working kid.

“Our results show that numerical concepts can influence how we reason about fairness,” the authors write.

And so your quest for cookies despite sloth depends on keeping your children from learning to manipulate numerical concepts. Of course (and perhaps worth mentioning), the reverse may also be true–your child’s development of a nuanced concept of fairness may depend on learning to manipulate numerical concepts. Who says math doesn’t matter in the real world?

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