Scientists at the University of Cambridge and the Rosie Hospital have shown that girls and boys often differ in what they pay attention to, even at birth. Finding these differences at such an early age indicates they may begin developing before birth.
According to the research, some psychological differences between males and females (such the development of social skills) may not just depend on the experiences we have growing up, but could also be influenced by prenatal biology too.
The study, published today in Biology of Sex Differences, involved 130 newborns at the Rosie Hospital. It builds on previous research by the same lab and uses robust methods to demonstrate the differences.
Previous research has shown that girls, on average, learn to talk earlier and develop social skills faster than boys. Studies have also found differences in brain structure at birth between males and females.
Scientists have long debated whether these differences are due to culture or biology. One way to answer this question is to test if differences are present soon after birth, before society and culture have influenced a child’s development.
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.
Professor Sir Simon Baron Cohen, Director of the Autism Research Centre, University of Cambridge
The new results align with the findings of a previous study published in 2000, which found that girls at birth on average looked longer at faces, and boys on average looked longer at objects.
In today's study, infants were presented with side-by-side moving videos of a human face and an object - a Newton’s cradle.
The team found that, regardless of sex, newborn infants generally preferred to look at the face. However, on average, females were even more likely than males to spend time looking at the face than at the object.
Since the test was done within hours of birth, the study suggests the differences are largely the result of biological factors before birth (such as hormone levels and genetics).
The new study used more robust methods compared to the original 2000 study. In particular, it included more consistent testing across all the babies involved and used more reliable methods to monitor what babies were looking at.
The researchers are continuing to follow the children included in this research to understand whether the differences observed shortly after birth have any effect on how each child develops - including how quickly they learn key social skills.
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.
Yumnah Khan, a PhD student at the Autism Research Centre, University of Cambridge
The research was led by a team from the Autism Research Centre in the University of Cambridge.
Earlier this year the centre received a $34.5 million philanthropic donation from K. Lisa Yang (opens in a new tab) to support research aimed at improving the health and wellbeing of autistic people and their families. The donation included $6.4 million to support the creation of The K. Lisa Yang Autism Clinical Centre, which will be based in the planned Cambridge Children’s Hospital (opens in a new tab).
They hope their work could lead to better understanding of neurodiversity and conditions such as autism, which is currently diagnosed about twice as often in boys than in girls.
The research was supported by Wellcome, the Simon Foundation Autism Research Initiative (SFARI), and a PhD studentship from Trinity College, Cambridge and the Cambridge Trust. The follow-up study is funded by the K. Lisa Yang Centre for Autism Research at Cambridge, which is part of the Yang Tan Collective.