Should boys play with dolls? Should girls play with trucks? The evidence is clear, and surprising.
The evidence on gender and toy preference shows both biological variation and strong environmental influence. Studies of toy preferences in infants before significant socialisation show modest differences in some toys (boys slightly prefer mechanical objects; girls slightly prefer faces). However, the magnitude of these differences is far smaller than the differences produced by socialisation, what children are given, what adults play with in front of them, and what messages they receive about who toys are "for."
Key citation
Alexander, G.M. & Hines, M. (2002). Sex differences in response to children's toys in nonhuman primates. Evolution and Human Behavior · Fine, C. (2010). Delusions of Gender. Norton
Research by Diane Levin and others shows that heavily gendered toy marketing narrows children's play, directing boys away from nurturing, language-rich play (dolls, small worlds) and girls away from spatial, construction play (blocks, vehicles). Both restrictions have developmental costs. Open-ended wooden toys sidestep the problem entirely: a wooden fox, a set of blocks, a stacking toy, these have no gender script. The child writes their own.
Gender-neutral, open-ended wooden toys →Britain's oldest toy maker. Every toy open-ended, wooden, and built for exactly the kind of play the research recommends.