Cambridge scientists have shown that girls and boys show differences in what they pay attention to, even at birth. Since these differences are present so early, it is possible they emerge due to prenatal factors.
It’s nature and nurture, not nature or nurture
Simon Baron-Cohen
The findings suggest that some psychological differences between males and females (such the development of social skills) may be influenced by both prenatal biology as well as later experience.
The study, published today in Biology of Sex Differences, involved testing 130 newborn infants only hours after birth. It builds on previous research by the same lab and uses robust methods to demonstrate the differences.
For years, research has shown that girls, on average, learn to talk earlier and develop social skills faster than boys. Scientists have long debated whether these differences are due to culture or biology. One way to answer this question is to test if sex differences are present soon after birth, before society and culture have influenced a child’s development.
A study from the University of Cambridge published in 2000 found girls at birth on average looked longer at faces, and boys on average looked longer at objects. Since then, scientists in the field called for a replication of this study. However, no research team has attempted this until now, since it is very challenging to carry out research on newborn infants.
In this new study, infants were presented with side-by-side videos containing a social stimulus, namely a human face with natural movement, and a non-social object, namely a set of metallic balls swinging due to gravity and their mechanical properties (a Newton’s cradle).
The team found that, regardless of sex, newborn infants generally preferred to look at the social stimulus. However, on average, female infants spent a greater proportion of the time looking at the social stimulus compared to male infants, while male infants spent a greater proportion of time looking at the non-social stimulus compared to female infants.
Since this is within hours of birth, before much postnatal experience (such as social expectations based on gender) has occurred, it is likely that prenatal biological factors that differ between the sexes during pregnancy (such as hormone levels and genetics) contribute to the observed on-average sex differences.
Yumnah Khan, a PhD student at the Autism Research Centre, University of Cambridge and the lead researcher on the study, said: “Our recent research has also shown that on-average sex differences are present in brain structure at birth and emerge prenatally. This new study tells us that there are not only on-average sex differences in the brain but also in attention and behaviour.”
Professor Sir Simon Baron Cohen, Director of the Autism Research Centre, University of Cambridge, who supervised the study, said: “This study addresses the age-old question of whether nature plays any role at all in shaping sex differences in the human mind and brain. The fact that we observe these differences within hours of birth, before extensive postnatal experience has occurred, suggests that prenatal factors play a role, and that these prenatal factors – sex hormones and/or genes – go on to interact with postnatal experience. In other words, it’s nature and nurture, not nature or nurture.”
The new study used more robust methods compared to the original 2000 study. In particular, it included more controlled experimental testing conditions as well as a more reliable method to monitor infant gaze. Crucially, the researchers who analysed the videos of the baby’s eyes were blind to the baby’s sex and whether the baby was looking at the social or the non-social stimulus, which ensured that they could not bias the results.
Dr Alex Tsompanidis, Assistant Research Professor at the Autism Research Centre and a member of the research team, said: “Sex differences at birth are important as starting points, but we need to remember that they don’t fully determine how children learn and develop in later life. This is because biological and social factors always interact, contributing to the rich diversity of human societies.”
Professor Carrie Allison, Deputy Director of the Autism Research Centre and another member of the research team, said: “The differences we see don’t apply to all male or all female infants, and are only seen when you compare groups of male and female infants, on average. There’s a lot a variation within, and overlap between, each sex. Our future research needs to better understand that variation.”
The team is now interested to find out if these early sex differences contribute to later differences in children’s minds, brains and behaviour. To test this requires a longitudinal (follow-up) study design, which is underway. The researchers hope that by understanding the origins of the earliest sex differences, scientists can better understand neurodiversity and conditions such as autism, which is diagnosed about twice as often in boys than in girls.
This research was supported by the Wellcome Trust, the Simon Foundation Autism Research Initiative (SFARI), and a PhD studentship from Trinity College, Cambridge and the Cambridge Trust. A follow-up study is funded by the K. Lisa Yang Centre for Autism Research at Cambridge, which is part of the Yang Tan Collective.
Reference
Khan, YT, Tsompanidis, A, Hymanson, E, Wickramanayake, S, APEX Consortium, Austin, T, Allison, C, & Baron-Cohen, S. Sex differences in social attention at birth. Biology of Sex Differences; 21 Sept 2026; DOI: 10.1186/s13293-026-00976-9
Republished from the University of Cambridge under a Creative Commons licence. Read the original article,
