A study conducted by researchers from the University of Cambridge indicates that behavioral differences between newborn boys and girls may emerge just hours after birth. The study involved observing 33-hour-old infants who were shown two videos: one of a human face and another of an animated Newton’s cradle. Both sexes spent slightly more time looking at the human face, but girls spent a greater proportion of their viewing time on the face compared to boys. Specifically, girls looked at the face for about 10 seconds longer than they did at the Newton’s cradle, while boys did not show a significant preference for either video.
The researchers suggest that these findings may indicate a preference for social interaction in girls, although they caution that the study does not establish whether these early differences predict future behavior. The research joins a broader discussion on sex differences at birth, noting that a 2025 review found no significant differences in fixation on human faces or in responses to crying between boys and girls.
Factors such as prenatal sex hormone levels, particularly the surge of testosterone in boys during early pregnancy, may contribute to observed behavioral differences. Additionally, researchers highlight the potential influence of gender socialization, suggesting that even subtle differences in how adults interact with newborns based on gender could play a role. They also note that girls may exhibit faster cognitive development, which could enhance their ability to process complex visuals like faces. However, the study acknowledges that the visual characteristics of the videos may have influenced the results, and further research is needed to clarify these findings.