New research has found robust sex differences in boys’ and girls’ toy preferences across a range of ages, time periods, countries, and settings.

The study, which was published in the scientific journal Infant and Child Development, found that children overwhelmingly chose to play with toys typed to their gender. Boys played with male‐typed toys more than girls did, and girls played with female‐typed toys more than boys did.

“For some people the topic of gender difference in toy choice is controversial, because they passionately believe that such gender differences should not exist. For other people the topic is trivial, because for them it is totally obvious that there are gender differences in toy choice,” remarked study author John A. Barry of University College London’s Institute for Women’s Health.

“My interest in this topic stems from my research into polycystic ovary syndrome (PCOS), a condition in which women have slightly elevated testosterone. The cause of PCOS is not known, but animal research suggests that the female fetus in a PCOS pregnancy is exposed to elevated levels of testosterone, programming for later development of PCOS.

“If elevated prenatal testosterone is the cause, then one of the effects we might see in childhood is increased interest of girls in male-typical toys,” Barry told PsyPost. “Thus, if we see greater interest in male-typical toys in PCOS girls, then this is potentially an important finding in helping our understanding of the cause and therefore potential cure for PCOS.”

For their study, the researchers conducted a meta-analysis of 16 studies from 1980 to 2016, which included a total of 787 boys and 813 girls (ages 1 to 8 years). A meta-analysis is a method used to statistically summarize the results of multiple studies.

The researchers excluded studies that relied on self-reported data from parents or children. Instead, the 16 studies in the meta-analysis were all observational studies of children in free play.

The studies were conducted in the United States, Canada, Europe, Israel and China.

The sex difference in toy preference held even after the researchers accounted for the effects of the presence or absence of an adult, the study setting, the gender equality status of the country, year of publication, and presence of gender‐neutral toys.

But that does not mean these factors had no influence. For example, the meta-analysis found that boys did play with male‐typed toys less when at home than when in a laboratory and girls played with female‐typed toys less in more recent studies.

“There is a fashion today to say that gender is purely a social construct. In reality, gendered behaviour is a mix of biology and social influence, and I think our meta-analysis supports this view,” Barry told PsyPost.

The study should not be misinterpreted as suggesting that boys and girls should only play with toys that correspond to their gender roles, he warned.

“I think the major caveat is that the findings of this study are descriptive, not prescriptive. In other words, the meta-analysis demonstrates, for example, that in general boys prefer playing with male-typical toys, but this is not to say that boys should play only with male typical toys,” Barry explained.

“The studies show that a minority of children play with gender-atypical toys. My interpretation of this is that playing with gender-atypical toys is a common and harmless variation on the norm, not to be discouraged.”

Previous research has found that children as young as 9 months-old prefer to play with toys specific to their own gender. But Barry said that many people still object to the idea that innate differences between boys and girls exist.

“Research into gender differences often attracts criticism which seems to be based on the moral judgement that biological bases for sex differences are somehow harmful to society,” he told PsyPost. “As scientists, and as members of the public who value truth over opinion, we need to move beyond moralistic arguments about facts and instead use the facts in beneficial ways (for example, understanding the cause of PCOS).”

The study, “Sex differences in children’s toy preferences: A systematic review, meta-regression, and meta-analysis“, was co-authored by Brenda K. Todd, Rico A. Fischer, Steven Di Costa, Amanda Roestorf, Kate Harbour, and Paul Hardiman.