Even Preschoolers Make Snap Judgments About Faces

Researchers have long known that adults make snap judgments about strangers. Seeing someone’s face for a fraction of a second (about 100 milliseconds) is all it takes to decide that they are trustworthy, mean, smart, or friendly. But how early do humans develop this impulse?

According to a study by a research team including Chicago Booth’s Alexander Todorov, children as young as four years old instinctively describe people’s faces using such traits. By the time children reach school age, they’re already using faces as clues to personality.

“You have this adage, ‘don’t judge a book by its cover,’ but we know from lots of research that people can’t help but do it,” Todorov says. “And, in fact, it seems to happen very early in development.”

Science has shown that children will make judgments about faces when prompted—when asked which face of several presented looks “nicer,” for example. But it hasn’t been clear whether kids think in trait terms on their own or learn to do so. That answer could be critical for designing interventions aimed at reducing bias, the researchers explain. If children spontaneously assign personality traits to strangers based on appearance, the roots of social stereotyping may begin earlier than previously understood. And if they don’t, it could be an indication that snap judgments are shaped by cultural exposure.

To study spontaneous impressions, the researchers tested a group of children aged 4–10. The children—nearly 200 from the United States and about 60 from the United Kingdom—were shown photos of unfamiliar faces and asked open-ended questions such as, “Tell me about this person.” The study design allowed the kids to describe anything they wanted including a person’s appearance, clothing, or emotions. They could even make guesses about the person’s life. The researchers showed the same photos and posed the same questions to about the same number of adult participants for comparison.

The researchers coded the thousands of responses, indicating whether they referenced personality traits (such as “nice,” “mean,” “smart,” or “shy”) or made nontrait observations (such as “has brown hair” or “looks happy”).

The kids who were involved in the study didn’t need prompts or leading questions; they volunteered personality judgments on their own. That basic pattern was observed in the youngest participants. The responses across the age range tended to cluster around familiar social traits such as kindness or meanness, friendliness, intelligence, and trustworthiness—the same broad dimensions that adults commonly use when judging faces.

However, the youngest children used fewer trait-based descriptions overall and relied more on obvious, surface-level observations. Older kids’ descriptions became increasingly rich, sophisticated, and trait focused—and gradually approached adult patterns, indicating important developmental changes in face perception.

The findings suggest to the researchers that the foundation of snap judgments forms early, while experience and cognitive growth refine the judgments over time. Think of this like learning to speak: the instinct presents early, but the capacity for language becomes more complex with age.

The study demonstrates that social perception is a deeply rooted human tendency, the researchers write. By the time children are old enough to ride a bike or read a chapter book, they’re already trying to make sense of people by reading faces and forming first impressions. Just as it does for adults, that instinct likely helps children navigate the social world by figuring out who seems friendly, safe, or approachable.

But the findings also suggest that the seeds of bias may be planted early, underscoring the importance of society’s role in shaping those first impressions.

Todorov points to previous research indicating that adults treat others differently on the basis of their automatic impressions. For example, adults tend to be gentler with a baby-faced kid than with one who looks less childlike. “We have lots and lots of evidence from adults that these impressions are not innocuous,” he says. Given the opportunity, “people will act according to their impressions.”

In this latest study, while the children aged 4–7 sometimes used trait characteristics to describe the faces they saw, they did so far less often than adults did. The findings suggest that there could, therefore, be a window of opportunity to intervene in ways that reduce bias as kids age. Future research could spell out how.