Sex differences in face looking preferences at birth.

While sex differences in behaviour have attracted considerable scientific interest, their underlying causes are complex and remain poorly understood. One approach to understand whether early biological factors might play a partial role is to study newborns, who have limited postnatal experiences. Previous research on neonatal sex differences is extremely limited, and studies that do exist have yielded mixed results, raised methodological concerns, and are yet to be replicated. To assess these gaps, the present study aimed to reevaluate sex differences in neonatal attention. 130 neonates (67 males, 63 females; mean age = 33 h) were presented with a video of a human face and a non-social object. When analysing percentage looking times, on average, females allocated a greater percentage of time looking at the face relative to males (d = 0.40). When analysing absolute looking times, females showed a preference for the face compared to the non-social object, while males showed no preference for either. However, no differences were observed between males' and females' absolute looking times for the face or object, indicating that sex differences are most prominent in the relative allocation of attention. Since sex differences in relative attentional patterns are present from the earliest days of life, one possible explanation for this effect may be due to contributions from prenatal factors (e.g., sex hormones). However, alternative explanations may be that these differences reflect general maturational differences between males and females or arise from low-level visual properties of the stimuli rather than their social versus non-social content.