See Baby Discriminate

More disturbing, Vittrup also asked all the kids a very blunt question: "Do your parents like black people?" Fourteen percent said outright, "No, my parents don't like black people"; 38 percent of the kids answered, "I don't know." In this supposed race-free vacuum being created by parents, kids were left to improvise their own conclusions—many of which would be abhorrent to their parents.

Vittrup hoped the families she'd instructed to talk about race would follow through. After watching the videos, the families returned to the Children's Research Lab for retesting. To Vittrup's complete surprise, the three groups of children were statistically the same—none, as a group, had budged very much in their racial attitudes. At first glance, the study was a failure.

Combing through the parents' study diaries, Vittrup realized why. Diary after diary revealed that the parents barely mentioned the checklist items. Many just couldn't talk about race, and they quickly reverted to the vague "Everybody's equal" phrasing.

Of all those Vittrup told to talk openly about interracial friendship, only six families managed to actually do so. And, for all six, their children dramatically improved their racial attitudes in a single week. Talking about race was clearly key. Reflecting later about the study, Vittrup said, "A lot of parents came to me afterwards and admitted they just didn't know what to say to their kids, and they didn't want the wrong thing coming out of the mouth of their kids."

We all want our children to be unintimidated by differences and have the social skills necessary for a diverse world. The question is, do we make it worse, or do we make it better, by calling attention to race?

The election of President Barack Obama marked the beginning of a new era in race relations in the United States—but it didn't resolve the question as to what we should tell children about race. Many parents have explicitly pointed out Obama's brown skin to their young children, to reinforce the message that anyone can rise to become a leader, and anyone—regardless of skin color—can be a friend, be loved, and be admired.

Others think it's better to say nothing at all about the president's race or ethnicity—because saying something about it unavoidably teaches a child a racial construct. They worry that even a positive statement ("It's wonderful that a black person can be president") still encourages a child to see divisions within society. For the early formative years, at least, they believe we should let children know a time when skin color does not matter.

What parents say depends heavily on their own race: a 2007 study in the Journal of Marriage and Family found that out of 17,000 families with kindergartners, nonwhite parents are about three times more likely to discuss race than white parents; 75 percent of the latter never, or almost never, talk about race.

In our new book, NurtureShock, we argue that many modern strategies for nurturing children are backfiring—because key twists in the science have been overlooked. Small corrections in our thinking today could alter the character of society long term, one future citizen at a time. The way white families introduce the concept of race to their children is a prime example.

For decades, it was assumed that children see race only when society points it out to them. However, child-development researchers have increasingly begun to question that presumption. They argue that children see racial differences as much as they see the difference between pink and blue—but we tell kids that "pink" means for girls and "blue" is for boys. "White" and "black" are mysteries we leave them to figure out on their own.

It takes remarkably little for children to develop in-group preferences. Vittrup's mentor at the University of Texas, Rebecca Bigler, ran an experiment in three preschool classrooms, where 4- and 5-year-olds were lined up and given T shirts. Half the kids were randomly given blue T shirts, half red. The children wore the shirts for three weeks. During that time, the teachers never mentioned their colors and never grouped the kids by shirt color.

The kids didn't segregate in their behavior. They played with each other freely at recess. But when asked which color team was better to belong to, or which team might win a race, they chose their own color. They believed they were smarter than the other color. "The Reds never showed hatred for Blues," Bigler observed. "It was more like, 'Blues are fine, but not as good as us.' " When Reds were asked how many Reds were nice, they'd answer, "All of us." Asked how many Blues were nice, they'd answer, "Some." Some of the Blues were mean, and some were dumb—but not the Reds.

Bigler's experiment seems to show how children will use whatever you give them to create divisions—seeming to confirm that race becomes an issue only if we make it an issue. So why does Bigler think it's important to talk to children about race as early as the age of 3?

Her reasoning is that kids are developmentally prone to in-group favoritism; they're going to form these preferences on their own. Children naturally try to categorize everything, and the attribute they rely on is that which is the most clearly visible.