The gender-neutral trend capitalizes on fears that parents have of inadvertently limiting their child’s potential. We want the best for our children; for daughters to grow up to be as competitive for STEM jobs as their male counterparts, and for sons to possess strong social and communication skills. But whether your child leans toward gender-atypical traits will likely have more to do with the prenatal environment —testosterone levels in utero — than a perfectly balanced upbringing.

In steadfast pursuit of gender equality and to promote nonconformity, it’s become popular in some social circles to start early, very early, by raising young children in a gender-neutral way: not revealing the baby’s sex at birth, dressing them and their bedroom in various shades of oatmeal, encouraging them to play with gender-neutral toys. There’s also pressure on corporations to help; parental complaints led Target to stop sex-segregating its toys, for instance.

Offering kids the opportunity to pursue what they’d like, freed from societal expectations, is an undeniably positive thing — whether it has to do with toys, clothing, or their future aspirations. But the scientific reality is that it’s futile to treat children as blank slates with no predetermined characteristics. Biology matters.

A large and long-standing body of research literature shows that toy preferences, for example, are innate, not socially constructed or shaped by parental feedback.

Most girls will gravitate toward socially interesting toys, like dolls, that help social and verbal abilities develop. Most boys will gravitate toward toys that are mechanically interesting, like cars and trucks, fostering visuo-spatial skills.

An immense body of neuroimaging research has shown brain differences between the sexes.

One recent study, published in Infant and Child Development, showed that these preferences emerge as early as nine months of age — before children are developmentally aware that gender differences exist, at around 18 months.

Another piece of evidence comes from studying girls who were exposed to high levels of testosterone prenatally, in the case of a genetic condition called congenital adrenal hyperplasia, or CAH. Girls with CAH tend to be gender nonconforming, and will prefer toys that are typical to boys, even when their parents offer more praise for playing with female-typical ones. This speaks to the vital role of hormones in developing gender preferences and sex differences in behavior, more broadly.

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