Newborn Baby Face Preference Study Reveals Early Sex
A 2026 Cambridge study of 130 newborns found girls spent more time looking at faces than boys within hours of birth, suggesting prenatal biological roots
Female newborns spent more time looking at a face than male newborns, who showed no clear preference, in a test of social versus nonsocial stimuli. The study provides the earliest evidence to date of sex differences in social attention, appearing at an average age of just 33 hours.
On average, female infants spent a greater proportion of viewing time looking at the social stimulus than male infants. Female newborns spent about 58.5 percent of their time looking at the face, while male newborns spent about 51.2 percent. Females spent more time looking at the face than at the mechanical object, whereas males did not show a clear preference for either stimulus.
Research builds on two-decade-old findings with improved methods
The study confirms and strengthens findings from the same lab published in 2000, which also found that girls at birth looked longer at faces and boys looked longer at objects. The new research used more robust methods, including more consistent testing and reliable monitoring of infant gaze.
Researchers tested 130 newborn infants at the Rosie Hospital in Cambridge within hours of birth. The sample included 67 males and 63 females. Each baby watched two videos side by side for up to 70 seconds. One video showed a young woman moving naturally, making eye contact, and occasionally smiling. The other showed a Newton’s cradle, a row of metal balls that swing and knock into one another.
Observers who manually judged where the babies were looking did not know the baby’s sex or which image appeared on each side, a blind analysis designed to reduce bias. The babies had very little experience outside the womb at the time of testing.
Differences likely rooted in prenatal biology, not experience
Researchers suggest the differences are largely the result of biological factors before birth, such as hormone levels and genetics. The study did not measure hormones or genes, but the fact that differences occur within hours of birth, before extensive postnatal experience, points to prenatal influences. Differences in early maturity could also be a factor.
Findings relate to autism and neurodevelopment, with follow-up underway
Understanding early sex differences may help understand neurodiversity and conditions such as autism, which is currently diagnosed about twice as often in boys than in girls. The team is conducting a longitudinal follow-up study to see if early sex differences contribute to later differences in mind, brain, and behavior.
The researchers are continuing to follow the children to understand if early differences affect later development, including social skill acquisition and autism risk. Professor Carrie Allison, Deputy Director of the Autism Research Centre, emphasized the variation in the findings. Average differences between males and females do not apply to all individuals and show substantial overlap. Sex differences at birth are starting points but do not fully determine later development, as biological and social factors always interact.
The research team was led by Ph.D. Student Yumnah Khan and supervised by Professor Sir Simon Baron-Cohen, director of the Autism Research Centre at the University of Cambridge. Dr. Alex Tsompanidis was also a member of the team. The researchers are conducting a longitudinal follow-up study to see if early sex differences in gaze contribute to later differences in mind, brain, and behavior.
