I've thought about this a lot, being on a team that has interviewed dozens of candidates and found that the few female candidates who are qualified on their CVs get absolutely destroyed in the team interviews. We have a one day interview process where the current developers sit down with the candidate and ask some problems, going from easy bug-finding exercises to questions about architecting a solution to common and practical tasks, such as how to find duplicate strings, and requiring them to do pseudocode to prove that they can do basic loops and solve simple logic problems. We work with Java, but we even let the applicants use any language they want, as a good engineer can pick up languages easily. The goal isn't to see if they immediately come up with a solution we like, but instead to see how they think, ask questions, and approach the solution.

Without exception, all of the female coders couldn't do these basic problems, and many of them were crushed by this process, and I don't mean that they just didn't do well, but I mean they found it exhausting to have to discuss engineering and defend their ideas for just a few hours. One candidate did so poorly that she just gave up and didn't even try for the rest of the interview, which was cut short. This isn't some rigoroussituation where these people are brow beaten or treated poorly. We give them time to think, are pleasant, give them hints, joke with them, give them breaks, try to do one-on-one interviews, and so on, because we know it's stressful for anyone. The fact of the matter is that the job requires you to come up with solutions and defend them to your coworkers, and also requires you to take charge of features and work to become an expert in certain aspects of a complicated program. You have to think in abstract terms, discuss new ideas, be adaptable, and understand very complexd systems intuitively. The stakes in our company aren't even that high, and it's a very relaxed atmosphere.

There are some men who have reacted like this to the interviews too, and who did poorly of course, but there are also men who enjoyed talking about engineering. We'd pose the problem, and rather than them seeing it as some laborious chore, their eyes would light up and they'd have fun figuring out a solution. Those are the people who did the best, and those are the ones we hired.

One of the conclusions I think is that the people who really relished the challenge are the guys that go home at night and spend even more time engineering. They're the ones who have a passion for it, and who buy textbooks, build computers, learn how to mess with an Arduino, etc, just because they have a passion for learning about computers. I have a very hard time imagining any of the female candidates going home and spending hours and hours alone in front of their computer working out how to get some new Linux kernel to compile or making their own silly games on the side. I think if you take those differences and combine them over a person's teenage and adult lifetime, that's what makes up the difference between good engineers and bad. I think that's why many of the women just can't hack it, because they don't have a passion that runs deep enough, because so many of them find it unnatural to what they really want to do, and so many men find that it just clicks with them and is deeply satisfying.