How we dress can even change the way we act. Studies have found that wearing more formal work clothes can get people thinking in a more abstract, big-picture way, and that adults become more focused when they put on lab coats — even if they’re not scientists. It’s not a stretch to think that putting our girls in tighter, frillier, flimsier clothes can imprint them with outdated notions about what they can and should do.

Though designs obviously vary from brand to brand, experts say that overall, the gender discrepancies in kids’ clothes are very real.

“Especially in the toddler years, the boys have more pockets, they have more fun active clothes than the girls,” said Francesca Sammaritano, a children’s wear designer and assistant professor of fashion at Parsons School of Design. “There’s leg room for bending your knees.”

The differences in cut — boxier for boys, narrower and more revealing for girls — have nothing to do with differences in children’s frames. Designers even use the same dress forms for both genders, Ms. Sammaritano said. “The body is the same, size-wise. You’re growing and developing in the same way until you reach six years, more or less.”

The gender divisions are a relatively new thing, said Jo Paoletti, a fashion scholar and author of “Pink and Blue: Telling the Boys From the Girls in America.”

“All you have to do is look at the last 30 years of consumer culture for children to see these stereotypes coming out more and more,” she told me. One reason, she said, is the rise in the 1990s of third-wave feminism, which embraced traditionally feminine looks; another is the prevalence of tests that let parents find out a child’s sex before birth, and have led to the trend of holding gender-reveal parties in pregnancy.

“Parents started reacting to that,” Ms. Paoletti said. “But all it means is, it prepares you to buy all the stuff — and prepares you mentally to be able to raise a human being — according to cultural stereotypes.”