If this is the same research that always gets cited, then it more accurately shows that boy and girl monkeys played with the wheeled toys an equal amount, but the girls played with the doll toys more.
That still shows a gender imbalance, but I find it interesting that it always seems to be used to imply that girls don't like trucks, rather than boys don't like dolls as much.
(A similar rhetorical trick is used when talking about favorite colours. Apparently lots of people's kids just love pink and this tells them it's all genetic, yet if you survey women their favourite color is the same as men, blue. They just collectively prefer pink more than men relatively speaking)
The preference for dolls is likely related to the role of females in childcare. Males are more the explorers and hunters. Women never explored nor hunted very much.
That still shows a gender imbalance, but I find it interesting that it always seems to be used to imply that girls don't like trucks, rather than boys don't like dolls as much.
(A similar rhetorical trick is used when talking about favorite colours. Apparently lots of people's kids just love pink and this tells them it's all genetic, yet if you survey women their favourite color is the same as men, blue. They just collectively prefer pink more than men relatively speaking)