KEY POINTS:
Behavioural differences between mothers of daughters and mothers of sons may be related to testosterone levels rather than sex stereotyping, Auckland University researchers have discovered.
The differences between mothers studied in their first interactions with their newborn babies were thought to be a result of stereotyping and conformity to social norms.
But Valerie Grant, a medical and health sciences researcher at Auckland University, and her team have found the behavioural differences may be because of varying maternal testosterone levels.
Evolutionary and developmental psychologists have shown that mothers of boys differ from mothers of girls even before their babies are born.
Women pregnant with boys are more likely to be anxious or angry during pregnancy, while women carrying girls are more likely to stay calm.
However, women pregnant with boys have better spatial skills.
The Auckland researchers have shown that mothers of daughters interacted with their babies by responding to the babies' vocalisations, whereas mothers of boys held them upright by the trunk and initiated more interactions with them.
Mothers of sons and mothers of daughters reacted very differently to videotapes of children behaving in a risky manner.
Mothers of two young sons were more likely to express encouragement of risk-taking behaviour than mothers of two young daughters, who in turn were nearly four times more likely to stop the tape when risky behaviour was shown.
Animal behaviourists noticed that dominant mothers had more male offspring more than 20 years ago and within a decade studies showed that human mothers had a similar tendency.
More recently, Dr Grant said, there had been the suggestion that mothers who had above-average female testosterone were more likely to conceive male offspring.
"If true, this could go some way to explaining most of these findings, since they are almost all potentially linked to variations in the mothers' testosterone levels."
- NZPA
