First take a look at these objects, some of the actual ones neuroscientists Amir Homayoun Javadi and Natalie Wee used in their study:
The two groups of faces are the same (though in a different order), three of a series of computer-generated faces made to look androgynous. If you saw more of faces 1-3 as male, and more of faces 4-6 as female, though, you're like the 30 subjects Javadi and Wee tested. The study authors had the subjects do some memory and counting tasks (a little more complicated than the above) with objects traditionally associated with women (like lipstick) or men (like motorcycles, because a man without a motorcycle is like a fish without ... something). Then they asked the subjects to choose the gender of the androgynized faces (the study included two more we didn't show above).
Somewhat surprisingly, looking at "womanly" objects like lipstick and earrings made subjects more likely to see an androgynous face as male, and vice versa — staring at motorcycles made faces look more female. This is called an "adaptation effect," in which looking at something for a long time makes you more likely to see its opposite. The study authors compare it to looking at a white screen after staring at red for a long time — the white screen will appear green. The fact that the adaptation effect occurs with objects and faces, they write, suggests that our brains have a centralized way of dealing with gender, which we apply to both objects and people. So looking at lipsticks is like staring at a screen that says "female," after which you're more likely to see something neutral as male.
The study authors aren't sure yet if there's a brain region specifically responsible for perceiving gender in both objects and faces, or if the region responsible for telling us lipsticks are for girls merely works in concert with the one telling us who is, in fact, a girl. Whatever the case, their research shows something else interesting — our perception of the "gender" of objects is apparently quite strong, strong enough to change our perception of the gender of people. The study subjects were between 18 and 24 years old, and it would be interesting to see this research done on younger people — when, exactly, do our brains learn that motorcycles are for boys?