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Does fetal testosterone influence how children play? December 19, 2009

Posted by Geekgirl in brain, Developmental, in the womb, social.
Tags: ,

I remember when my son was little, parents tried very hard to have their children of either gender play with both “girl and boy” toys. Yet, if you ask most parents, it just didn’t work most of the time. Children are born who they are. Since that time, there has been quite a bit of research showing that, typically, girls naturally choose girl toys and boys naturally choose boy toys.

But not always. So, why do children choose girl toys or boy toys? Do girls exhibit ‘male typical play’ and vice versa? And why?

These researchers did the following experiment. In a nutshell, they measured the amount of testosterone in the amniotic fluid of pregnant women. Then, as those children grew up, the parents were asked standardized questions about their childrens play and behavior. The result? The more testosterone that the fetus was exposed to, the more likely the child was to engage in “male typical” play. This held true for both boys and girls. There were about 200 children in the study and the average age of the child at the time of the survey was eight years old.

I’ve abbreviated the research article, but since it is publicly available, I’ve included the pdf.

fetal testosterone

The authors also make another interesting point. Previous studies have found a correlation between the amount of testosterone and male typical play in girls but not boys. These experiments relied on measuring the amount of testosterone in the mother’s blood, not the amniotic fluid. Since a fetus has direct exposure to amniotic fluid but not the mother’s blood, using this method makes the data more reliable. How the experiment is done is always critical to the results.

Fetal Testosterone Predicts Sexually Differentiated Childhood Behavior in Girls and in Boys

Copyright © 2009 Association for Psychological Science

February ; 20(2): 144–148.

Bonnie Auyeung1, Simon Baron-Cohen1, Emma Ashwin1, Rebecca Knickmeyer1,2, KevinTaylor3, Gerald Hackett4, and Melissa Hines5

1Autism Research Centre, Department of Psychiatry, University of Cambridge; 2Department of Psychiatry, University of North Carolina at Chapel Hill; 3Department of Clinical Biochemistry, Addenbrooke’s Hospital, Cambridge, United Kingdom; 4Department of Fetal Medicine, Rosie Maternity Hospital, Cambridge, United Kingdom; 5Department of Social and Developmental Psychology, University of Cambridge


Mammals, including humans, show sex differences in juvenile play behavior. In rodents and non human primates, these behavioral sex differences result, in part, from sex differences in androgens during early development. Girls exposed to high levels of androgen prenatally, because of the genetic disorder congenital adrenal hyperplasia, show increased male-typical play, suggesting similar hormonal influences on human development, at least in females. Here, we report that fetal testosterone measured from amniotic fluid relates positively to male-typical scores on a standardized questionnaire measure of sex-typical play in both boys and girls.

These results show, for the first time, a link between fetal testosterone and the development of sex-typical play in children from the general population, and are the first data linking high levels of prenatal testosterone to increased male-typical play behavior in boys.

Sexual differentiation of the mammalian brain occurs under the control of gonadal hormones, particularly androgens, during early development.  Manipulating androgens prenatally or neonatally permanently alters brain regions and behaviors that show sex differences  For instance, in rodents and non human primates, treating developing females with testosterone or other androgens increases male typical play, whereas reducing androgens in developing males reduces it. Androgen exerts similar effects on sex-typed reproductive behaviors and on neural sex differences.

In humans, sex differences in toy preferences have been observed in children as young as 12months of age , and these differences, along with sex differences in playmate and activity preferences, grow larger as children progress into middle childhood. The strongest evidence that androgens influence human sexual differentiation comes from studies of play behavior in girls exposed to abnormally high levels of androgens because of congenital adrenal hyperplasia(CAH), a genetic disorder that causes excess adrenal androgen production beginning prenatally.


Participants were recruited from a longitudinal study of the effects of fetal testosterone on child development. All mothers had undergone routine amniocentesis in the Cambridge, UnitedKingdom, region and given birth to healthy singleton infants. Materials for the present study were sent to all 452 available mothers, who were asked to complete a questionnaire about their child’s activities and interests. Complete information was obtained for 112 male and 100 female offspring (mean age = 8.59 years, SD= 0.97 years, range = 6.38–10.30 years). No significant differences were observed for the predictor or control variables between the larger and current sample in this study.


Outcome Variable—The Pre-School Activities Inventory (PSAI) is a psychometric scale,with established validity and reliability, developed specifically to assess variability in sex typical behavior within each sex. It includes 24 items and is completed by a parent to describe the child’s behavior. Higher scores reflect more male typical behavior, and females with CAH obtain elevated (more male-typical) scores on the PSAI in comparison to unaffected female relatives (Hines, Brook, & Conway, 2004),suggesting sensitivity to the effects of prenatal androgen exposure.

Predictor Variable—Amniotic fluid samples were collected between weeks 11 and 21 of gestation. This timing coincides with the hypothesized critical period for human sexual differentiation, which is thought to occur between approximately weeks 8and 24 of gestation. Fetal testosterone was measured in amniotic fluid.

Control Variables—Gestational age at amniocentesis, maternal age, maternal education,and child’s age at PSAI assessment were included for control purposes. Gestational age and child’s age were assessed from medical records.


As expected, boys had higher amniotic testosterone than girls in general  Boys also had higher PSAI scores. Maternal education, maternal age, child’s age, fetal testosterone levels, sex, and the interaction between sex and fetal testosterone were included in the analysis  The only significant predictors included in the final model were sex and fetal testosterone.

Within-sex analyses on the full data set indicated that testosterone correlated positively with PSAI scores for both girls  and boys. The size of the correlations between PSAI scores and fetal testosterone level did not differ significantly between the sexes.  For within-sex regression analyses, the same predictor variable selection procedure described above was used. For girls, maternal age, child’s age (suppressor), and fetal testosterone levels were included in the analysis. Fetal testosterone level was the only significant predictor retained in the final model,  For boys, fetal testosterone level and maternal age were entered in the analysis. The final regression model for boys retained both fetal testosterone level and maternal age.


We found a significant relationship between fetal testosterone and sexually differentiated play behavior in both girls and boys. The large sample and the specific measure used may account for our ability to detect this relationship, even though two prior studies did not detect it.

Because children in the current study were developing typically, and because measures of testosterone were taken directly from the fetal environment, our results strengthen the evidence that testosterone plays a role in sexual differentiation of human behavior.

Prior studies linking prenatal testosterone to childhood play have relied on clinical populations or measures of maternal hormone levels. Our study avoids problems of interpretation associated with those approaches. Our results also differ from prior findings in that we found a relationship between prenatal testosterone and sex-typical play in both boys and girls. In contrast, studies of children with CAH have reported elevated male-typical behavior in girls but not boys, and the prior study relating maternal testosterone during pregnancy to childhood behavior found a relationship in girls but not boys.

Thus, our data are the first documentation that androgen exposure prenatally relates to sexually differentiated play behavior in boys and in girls. In addition, the current results support an organizational, as opposed to current, activational role of testosterone, because play behavior is measured in childhood, when concurrent testosterone levels are low.Prior difficulty finding predicted relationships between testosterone and behavior in boys may reflect the use of approaches that are not well-suited to its detection. Boys with CAH, unlike girls, may adjust testicular androgen production prenatally, thus avoiding marked androgen elevation, and testosterone in mothers and daughters correlate, whereas there is no correlation between testosterone in mothers and sons, making maternal samples less useful for detecting hormone-behavior relationships in boys. Therefore, studies relating amniotic fluid testosterone to subsequent behavior may be particularly useful for elucidating the role of testosterone in the behavioral development of boys.


This work was supported by grants from the Nancy Lurie-Marks Family Foundation and the Medical Research Council(to S.B.-C.) and by National Institutes of Health Grant HD 24542 (to M.H.). B.A. was supported by a scholarship from Trinity College, Cambridge. We are grateful to the families who have taken part in this longitudinal study over many years and to Ian Goodyer, Greg Davis, and Ieuan Hughes for valuable discussions



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