The pull of Guyland reminds us that women cannot accomplish this transformation alone. In the book's final chapter I argue that just as men need to stand up, do the right thing and break the silence that perpetuates Guyland, so, too, do women need to support each other in resisting its pull.

My colleagues and I have done a survey of 13,000 students on more than 17 campuses, and we found that while sex in college has always been a bit more casual, "hooking up" has pretty much replaced other traditional forms of dating.

So guys who are otherwise sensitive and thoughtful say and do ridiculously dumb things to impress other guys. It's an enormous performance, but guys know that if they fail, they'll be ridiculed as sissies mercilessly.

Guys constantly talk about pornography in two ways: as revenge and as reassurance. When you live in a world in which beautiful, sexy women are all around you, in the same classes, on the same athletic field, competing for the same jobs, then the pornographic world - the world in which women thrill to male sexual desire - reassures men that although they may feel "one down," they're still entitled to women's bodies.

Many boyfriends or close male friends seem so different when they are by themselves, as opposed to when they are with a bunch of other guys. I think it has to do with the desperate desire on the part of guys to be seen as a "real guy" - a real man, a man's man.

It's like what you might call Goldilocks' dilemma in the old fairy tale. Young men see women as "less than" or "better than," but never their equals. And studies indicate that equality is the best foundation for a healthy relationship.

The good news is that women's roles have changed so dramatically over the past three decades that women now expect to have careers, balance work and family, express their individual autonomy.