I have question on men and girls chess?

at gm level how come men are better than girls at chess? any ideas

Especially as evident by J. Polgar reaching the rank of #8, this question is invalid.

There are many theories as why there is more women in the upper echelon. (Not saying that men are better.)
1. Women prefer to have lives instead of "mastering" this inane game.
2. Men are more likely to have autism, which helps in this specific game. (There is an alternate theory that women suffer from these disorders but the systems are different so they haven't been diagnosed correctly.) (Proposed by @ZefCat.)
3. The brains are wired differently so men have the more spacial/mathematical mind which is helpful for this waste of time activity.
4. Girls are taught from a young age to be pretty and not damage the frail male ego. Boys are taught to win at any costs.
5. As a heavily dominated male activity, women are an oddity at a chess tournament. Even if they're not ogled in a sexual manner, they are stared at and must feel uncomfortable due to this. Even at scholastic events, I find that the mothers are treated like nerd at a sporting event.

re. point 5, I've heard there is some psychology component going on when women play men OTB, men might be more aggressive and women more passive. I'm not sure if they looked at online chess.

btw, lots of people do it including me sometimes by accident, but in most situations we shouldn't call women girls.

Some ideas:

* "There are tournaments for girls and tournaments for people" --> Girl elos are collected in women tourns and thats not where the super GMs play, so there is no exchange of experience and elo points on this level, the avaerage elo is much lower. Girls also may not be taken serious when they get granted these advantages. Look at Hifan You who dosnt play in girl tournaments - she is the highest ranked woman. Judith Polgar also didnt do it - I think, girls should not play in girl tournaments. They should also reject girl prices.

* A girl playing in a man super tourn is still the outsider. No one expects her to win. It is also a statistical thing, if one girls plays in a tourn with seven men, then there is just a 12.5% chance that a girl wins. Super tourns should have the same amount of girls and boys.

* Girls have no female trainers. There may be a chess school specific to girls talents, but girls wont find out unless they train together. Ask the Muzychuk sisters.

* Girls are not supposed to play chess.

@jonesmh Well judging by the fact that there is not a single women grandmaster above 2700 elo at the moment, the question is valid.

Some papers show that women perform below their strength when playing against men, and other state that women perform above their strength. One paper from, using chess games played over the internet, found that women perform worse when they think they're playing against a man. (They scored 50% when they don't know the opponent's gender, but scored <30% when they thought the opponent was a man, although they played the same opponent both times [all four game].)

@Chess-Gamer Well judging that Judith was above 2700 and has beaten every world champion that's alive, that proves that women can perform at this level and aren't simply worse at chess.

You're only talking about one person. She doesn't even play anymore...