Male monkeys prefer boys' toys

"It's thought of as a sexual stereotype: boys tend to play with toy cars and diggers, while girls like dolls. But male monkeys, suggests research, are no different (see a related video report).
This could mean that males, whether human or monkey, have a biological predisposition to certain toys, says Kim Wallen, a psychologist at Yerkes National Primate Research Center in Atlanta, Georgia.
Wallen's team looked at 11 male and 23 female rhesus monkeys. In general the males preferred to play with wheeled toys, such as dumper trucks, over plush dolls, while female monkeys played with both kinds of toys.
This conclusion may upset those psychologists who insist that sex differences – for example the tendency of boys to favour toy soldiers and girls to prefer dolls – depend on social factors, not innate differences." link