Even more surprisingly, sex-typed toy interests have been found to exist in non-human primates such as vervet monkeys and rhesus monkeys.”
—Professor Melissa Hines
“The overall conclusion, based on all these types of research, is that children’s toy preferences relate to the prenatal hormones they were exposed to.”
A steady stream of popular books on how to understand male and female behaviour has suggested that there are hard-wired differences in the brains of women and men and that these intrinsic differences shape our lives and give rise to important differences in social roles and occupational achievement.
The picture that has emerged from rigorous scientific research over the past 50 or so years is, however, rather different. Studies of genetics, prenatal hormones and postnatal socialisation, along with comparisons with other species, now strongly suggest that:
• There are indeed some inborn contributions to differences in gender-related psychology and behaviour,
• But that postnatal socialisation is important as well,
• And that the two types of factors interact in complex ways.
In addition, the myriad types of behaviours that differ for males and females also differ in the formula for combining inborn factors, postnatal socialisation and their interactions to determine outcomes. Indeed, this is why individuals within each sex can differ so dramatically from one another in gender-related behaviours.
Begin with differences in the sex chromosomes, XY for males, XX for females.
• These sex chromosomes contain genes that cause the gonads to develop as testes or ovaries.
• If testes develop, they begin to produce the hormone, testosterone, by about week eight of gestation, causing males to have more testosterone exposure during gestation than females.
• Recent evidence shows that these differences in testosterone levels prenatally relate to the toys that children prefer.
• Higher levels of testosterone are associated with stronger preferences for toys like cars, trucks and weapons, and weaker preferences for toys like dolls.
Not only do boys tend to play with trucks whereas girls tend to play with dolls, but within girls, those who are less interested in dolls and more interested in trucks tend to have been exposed to higher levels of testosterone during gestation,” she says.
“Even more surprisingly, sex-typed toy interests have been found to exist in non-human primates such as vervet monkeys and rhesus monkeys. These observations have led to reconsideration of the roots of children’s toy preferences, which now seem to be more than rehearsals for adult roles. We know it is not the shape or colour of the toys. We think it might be linked to movement.”
In addition to these inborn influences, sex-typed behaviours, such as toy preferences, are partly learned.
• Parents, peers and teachers encourage children to play with sex-typed toys and discourage them, particularly boys, from playing with cross-gender toys. Imitation of people of the same sex, and responses to information as to what is for girls or for boys also are key factors.
• Experiments have shown that children tend to like the objects that they see others of the same sex choosing and that they play more with objects that they have been told are for children of their own sex.
Stereotypes aside, there is also a danger in generalizing. Differences and variations in gender-related behaviour are complex and subtle.
• Once a child is born a huge array of factors come into play, interacting with and expanding upon the influences of early hormone exposure.
• “It’s also important to remember that the variation across individuals within the same sex is far greater than that between the sexes,”
Although we are born with certain tendencies, our brains and our behaviour can and do change over time as we are exposed to different environments.