When I did Psych, there seemed to be more females than maless, but it wouldn't have been 90/10. Probably about 65% females? At a guess...
You definitely shouldn't let gender decide whether or not you want to do a course. It should be based on whether or not you actually like it!
My two majors (anthropology and philosophy) are interesting. Anthropology is definitely dominated by females while philosophy is dominate by males (it depends on what type of philosophy for some extent, continental seems to attract more females to put the ratio at around 50/50 but analytic/applied is definitely male dominated). Interestingly, in subjects that are dominated by males, there is usually much less opportunity to get a word in, but I feel more compelled to join in on the debate in order to cut through all the bullshit that's being said and the debate can get both lively and obscure, which is entertaining. In female dominated tutes, there seems to be less talking overall, but it at least seems as though people have done the reading and everyone knows what they're talking about. This could reflect the subjects I've been doing, rather than gender though, and come to think of it, philosophy probably does attract the 'let's say stuff for the sake of sounding clever'-type.