The surprising way girls and boys behave differently just hours after birth

It’s an age-old question: How much of the differences between the way men and women behave are a result of nature, and how much is nurture?A new study could shed more light on this.It shows different behavior between newborn boys and girls could appear just hours after birth.Researchers from the University of Cambridge believe forces at work before birth — like sex hormone levels, might play a role, or even that the changes are a result of a slightly faster cognitive development in newborn girls.They showed newborns — only about 33 hours old — two videos.

One was a human face, the other, an animated Newton’s cradle (swinging metallic spheres).Both sexes spent slightly longer looking at the face than at the Newton’s cradle.But researchers found that girls spent proportionally more of their looking time on the face than boys did.In terms of absolute time spent looking, girls looked about 10 seconds longer at the face compared to the Newton’s cradle, while the boys didn’t have a significant difference between the time spent looking at either video.The researchers say this suggests girls had a preference for the face, while the boys didn’t show a preference.You might assume this means that girls are naturally more social, with an innate interest to be with and interact with other humans.

Unfortunately, it’s not that simple.This study didn’t follow the newborns as they grew, so it can’t tell us whether these early differences predict later behavior.We can only say that, at around 33 hours old, girls in this experiment showed a stronger preference for the face than boys did.It’s also important to note that this study joins a body of research that doesn’t tell a clear story about sex differences at birth.

A 2025 review of research on this subject found that there was no significant difference between boys’ and girls’ fixation on human faces.They also found there wasn’t any difference in boys and girls when it came to “contagious cryin...