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.

Some of the worst elements of Guyland rest on the twin pillars of men's silence and women's compliance.

Many guys see relationships with women as a zero-sum game: If she wins, he loses. Marriage is the ultimate contest: Her job is to get him to capitulate to marriage. So many men see marriage as the "end of freedom," the end of boyhood. That's why bachelor parties are supposed to revel in that boyish irresponsibility "one last time." So many guys figure, "Why rush into something that means basically that you'll be a prisoner forever?"

Playing along with Guyland may be the only way an individual woman might believe she has a chance at a social life or a relationship. Sometimes it gets pretty crazy, like a sorority requiring that all the pledges sleep with the members of the "brother" fraternity.

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.

Young men are eager to "hook up" with women. And many say they have very good female friends. But some of the emotions circulating among guys make it difficult to form and sustain healthy relationships.