A boy who assaults once in high school may not do it again, which in some ways is good to hear. At the same time, that means a seemingly “good guy” may well do a bad thing. A very bad thing. And afterward it is completely plausible for him to get away without apologizing, facing consequences, making amends. The monster-good guy dichotomy contributes to his denial: He could not possibly really be a rapist because that would make him a “monster,” and he is a “good guy.” So he rationalizes, forgets, goes on to professional success and even a happy marriage. Meanwhile, he may have derailed the life of another human being, causing her years, decades, of pain and trauma.

It is natural for parents to think their own sons would be incapable of sexual misconduct, but that does not absolve them of responsibility for educating their boys. Yet according to a survey of more than 3,000 18- to 25-year-olds published last year by the Making Caring Common project, which is part of the Harvard Graduate School of Education, more than 60 percent of respondents had never had a single conversation with their parents about how to be sure that your partner wants to be having sex with you. A similar share had never been told about “the importance of not pressuring someone to have sex with you.”

Essentially, said Richard Weissbourd, the lead author of the survey, parents have abdicated responsibility for talking with their children, especially their boys, about sexual ethics or emotional intimacy. “If you ask many parents whether it’s really important that your son has a lot of integrity and is a good person, they would absolutely say yes,” he said. “But if you were to ask, ‘Have you talked to your son in a concrete way about the many ways you can degrade women?’ Most parents, I think, would say no.”

Other research has found that parents are vastly more likely to talk to their daughters about sexual readiness and disease protection, perhaps because they believe girls are more vulnerable, emotionally as well as physically. But that leaves boys to learn appropriate behavior from one another as well as the digital street corner.

In locker rooms, fraternity houses and other all-male spaces, they hear that sex is about conquest, about asserting masculinity through domination of girls’ bodies. “It’s not like guys say, ‘Dude, I made her feel great!’” a high school junior in New England told me. “That never happens. It’s always, ‘Bro! I slammed her!’” They’ve banged, they’ve nailed, they’ve smashed, they’ve torn up, they’ve destroyed. It all sounds less that they’ve had sex than that they’ve just returned from a visit to a construction site.

Boys grow up in a world in which women are either hyper-sexualized or absent. In the G-rated movies little boys watch, according to researchers at the University of Southern California, fewer than a third of the speaking characters are female — a figure that has held steady over the 10 years it has been tracked — and the percentage of skin women show is similar to that in R-rated movies (and that’s not because R-rated movies have gotten more conservative).

By their teen years, according to survey results released this month by PerryUndem, a research and polling firm, about half of boys say that several times a week or more they see female characters in video games presented as “hot,” as well as “unrealistic images” of female bodies, or “women whose bodies are more important than their brains or abilities” on TV and in movies and videos. Frankly, 50 percent seems low — and “unrealistic portrayals” an almost comic euphemism.