Alex McKay recalls being startled when the 13-year-old boys he was addressing in a Toronto sex-education class began peppering him with graphic questions. “A lot of the questions, I soon realized, revolved around these young boys having looked at pornography,” said Mr. McKay, research director for the Sex Information and Education Council of Canada. The boys were preoccupied with how well-endowed the male porn stars were, not to mention their bizarre habit of ejaculating on their partners’ faces. “What a lot of their questions boiled down to was, ‘Is what I’m seeing in the porn that I’m watching what sex is really supposed to be like? Is this how I am supposed to behave?’ ” Mr. McKay recalled. The proliferation of online porn means the sorts of questions Mr. McKay first encountered at the dawn of the Internet age in the 1990s arise ever more frequently as teens and even preteens come into contact with sexually explicit images. Despite parents’ best efforts to shield their children, about 40% of those aged 10 to 17 are exposed to online pornography, one recent U.S. study found. Porn has moved from dingy bookshops to the mainstream, a trend reflected in the opening scene of last year’s comedy hit Superbad, in which the high-school-age characters discuss the merits of various hard-core Web sites. To researchers at Brigham Young University, today’s youth are “Generation XXX.” Their study of students at six U.S. universities found that viewing porn has become as accepted an activity as having a few beers at the pub. “Results suggest that pornography is a prominent feature of the current emerging adulthood culture,” the authors wrote. Less clear is how this growing pastime is affecting sexual relationships. Mr. McKay said parents and educators need to do a better job preparing children for the new age. “The Internet’s not going away, and pornography is certainly not going away, so the pertinent question is how are we teaching young people to deal with it, and that’s a question that most people don’t want to ask,” he said. Kim Martyn does not shy away from the subject in her job promoting sexual health to youth for Toronto Public Health. She has worked in the field for 25 years and says there is nothing new about young guys learning from pornography; what has changed is that the images are so readily available, and they are “more raw, more hardcore.” Ms. Martyn worries about the detrimental effect such content has on young viewers lacking sexual experience and media awareness. “I don’t think that serves them well in terms of their relationships and what they expect from themselves,” she said. In her teaching, she introduces the subject of pornography to students as early as Grade 5, advising them how to deal with unwanted exposure to porn. “We talk about pop-ups and what to do with that,” she said. It is better they be prepared, she reasons, “than ashamed and scared to tell someone that this is on the computer.”

She is also troubled by the hateful nature of the pornography kids are most likely to stumble across in a cyber world where women are routinely referred to as sluts and bitches. “The cheap stuff is often the worst stuff in terms of misogyny, in terms of using images of really young girls,” she said. “None of that serves to inform young people, male or female, what healthy sexuality is about.” Despite inhabiting a hyper-sexualized — some have called it “pornified” — world, today’s youth are not necessarily better informed, Ms. Martyn said. “They might know there’s something called anal sex. They might know something about oral sex.… They all know about transgender,” she said. “But they don’t know the basic stuff relevant to them. They don’t know how you can tell if someone likes you. They still have no clue in terms of when you know if you’re ready to have sex.” Francine Duquet is a professor of sexology at Université du Québec à Montréal researching the hyper-sexualization of teenagers. It was not that long ago that magazines showing a little too much flesh were stopped at the border, and you had to be 18 to purchase the relatively tame likes of Playboy. Now she comes across children whose natural curiosity has led them to porn sites featuring bestiality and group sex. Children aged 13 and 14 ask whether sex necessarily involves three orifices, she said. “What we have to make young people understand is that sexual relations are, above all, relations with another person. It is not a matter of genital acrobatics. I always tell young people that it’s not the Cirque du Soleil of sex. It’s a relationship with another person who has his modesty, history, desire and limits,” she said. “It’s not just a matter of orifices and appendages.” Sylvain Boies, a psychologist in Victoria, was one of the first researchers to begin looking at the effect of Internet pornography. In a 2002 survey of Canadian university students, he found that more than 40% used the Internet for sexual entertainment, and that nearly half of those had started at age 16 or younger. He suspects those numbers have only gone up with the spread of the Internet. “Adolescence is a period of exploration. That’s very normal,” he said. “At the same time, it creates the foundation for intimacy. It sets the tone for how they will create deeper affiliations with other people. Certainly, if the images of intimacy and sexuality that they see are pornographic versus even erotic, that creates for a lot of young men … the idea that women are always ready and available and want sex all the time. That’s what they see in the images.” He witnesses this phenomenon among men in his practice. “There is a whole industry telling them what their sexuality is about,” he said. “Consumers of pornography start believing that’s what sex is about. What is removed is the intimacy.” In a 2003 article in New York magazine, feminist writer Naomi Wolf described the effects of the new porn culture on young women. “Now you have to offer — or flirtatiously suggest — the lesbian scene, the ejaculate-in-the-face scene,” she wrote. “Being naked is not enough; you have to be buff, be tan with no tan lines, have the surgically hoisted breasts and the Brazilian bikini wax — just like porn stars.” She recounted conversations with college-age women who feel “that they can never measure up, that they can never ask for what they want; and if they do not offer what porn offers, they cannot expect to hold a guy.”