University of Otago researchers say they have discovered a new way to understand subtle differences between male and female behaviour.
They say a hormone called mullerian inhibiting substance works on the brain to create behaviour that is generally thought to be masculine.
The substance is only found in males, and scientists have known for decades that it plays a role in the development of reproductive organs.
Neurobiologists at the University of Otago say trials using mice show it also works on parts of the brain unrelated to sex.
One of the researchers, Associate Professor Ian McLennan, says male and female mice exhibit different tendencies. Male mice, for example, show a greater interest in exploring and moving beyond boundaries than female mice.
Professor McLennan says males with lower levels of MIS showed less interest in exploring new environments.
He says a three-year study of the hormone in five-year-old and six-year-old children has been under way for 12 months, to try to determine the effect of the substance on people.