While on the campaign trail Donald Trump was criticized for an incident in which he performed an exaggerated and unflattering  impression of journalist Serge Kovaleski, a Pulitzer-prize winning journalist with a physical disability. While Mr. Trump insists that he was not mocking Mr. Kovaleski—and instead pointed out that he referred to Mr. Kovleski as “a nice reporter”—his nonverbal signals told a different story.

Those signals probably sent a powerful message. Recent research has explored whether young children develop bias against people by watching the nonverbal displays of the adults around them. The findings are worrying as they suggest that children can “catch” prejudice that they observe in adults, even when the bias is more subtle than that demonstrated by Trump.

In our forthcoming paper in Psychological Science, four- and five-year-old children observed adults display negative nonverbal signals, scowling and using an unfriendly tone of voice toward one person, while displaying positive nonverbal signals to another person. Moments later, children showed a bias in the same direction—favoring the person who received positive nonverbal signals.

This research shows that children are very sensitive to the cues adults provide about who they like and who they don’t like, who is thought of as “good” and who is thought of as “bad” by others around them. In other words, children can “catch” bias from adults even when adults don't explicitly teach it to them, demonstrating that adults’ unspoken biases can impact the social biases of the children around them. This means that children do not just pay attention to the things we say, they also pay attention to how we convey our preferences.

Of course we can think of many reasons this might be a reasonable strategy for young children to adopt. When a mom scowls at the neighbor it may be for good reason—perhaps he is someone she would like her children to avoid. But our findings suggest that children will take this bias one step further. Children did not just develop a bias against the individual who they saw the nonverbal bias demonstrated against. Their biases spread to a friend (who was also portrayed as a member of the same group) of the individual who received negative nonverbal signals.  The fact that biases were extended to others suggests that this process may lay the foundation for larger intergroup prejudices to develop.

But outside of the research lab, children might get mixed signals, just as Trump appeared to mock Mr. Kovaleski while also calling him nice. What matters most, our words or our actions?

Researchers Luigi Castelli, Cristina De Dea and Drew Nesdale, ran just this experiment. They showed White children a White actor displaying nonverbal bias against a black person while saying overtly friendly or neutral statements. Subsequently, the researchers examined the children’s attitudes toward the Black person, finding that children seemingly ignored the verbal messages they heard. Children who saw a white actor displaying negative nonverbal signals toward a black person showed negative attitudes toward the black actor whether they had heard the actor verbally address the black actor positively or neutrally. Even more worryingly, in a follow-up study, children not only showed bias against the original black person, but also against a new black person they hadn’t seen before.

What does this all mean? Children are looking to the adults in their world to understand what is right but also who to like or approach and who to avoid or distance from. When children see the adults in their lives, or on TV, show nonverbal bias, they take in this information, incidentally learning to think that some people are better than others. In fact, they may even take it one step further—learning to think that some groups are better than others.

Ultimately, this new research suggests that we can involuntarily communicate our own biases to our children through our nonverbal behaviors. This means that ultimately we, as adults, need to be more conscious of the biases that we may be modeling for our children. Given how easily children catch social biases from the adults around them, we might begin to think about the messages we are sending our children, both spoken and unspoken.