This seemed to be a good summary:

Many recreational chess players are excited by the prospect of studying the dozen or so major variations on the king’s pawn opening, each of which comes with its own sub-variations? If your instinct tells you that males will be disproportionately drawn toward this kind of intense practice style than females, you’re correct. Studies show that boys and men are more likely to exhibit a “rigid persistence in an activity,” by which “the passion controls the individual” (“obsessive passion” in the literature). In anecdotal terms, we are talking here about the man who drops everything to become, say, a 16-hour-per-day videogamer, or a day-trader, or chess addict. Yes, some women take on these kinds of fixations. But men do it more often, and with greater intensity. Not only do males generally score higher than females in these areas, but there is also a positive relationship between obsessive passion and both chess and Scrabble ratings. The sexes don’t seem to differ in the benefits they gain from practice. But men do tend to enjoy practice more, and so do more of it; habits that are strongly associated with winning. The bottom line: Plausibly, one of the main reasons why there are more elite male chess players is that boys are simply more motivated to do what it takes to become an elite player.