It was suspiciously warm, the reception given to a study published a week ago in the Journal of Sexual Medicine. A survey of 4,600 young people in the Netherlands, aged 15 to 25, found the behavioral impact of pornography—most of it online now—to be surprisingly small. Reaction to the news? People didn't whoop exactly. But you know they wanted to.

Pundits loved the contrarian view, parents loved being let off the hook. Of course, to the study's author, who said "previous studies could have overestimated the association between pornography and sexual behaviors," there is a better response: Sure, fella. The same way we overestimated the association between alcohol and reckless driving. Let me take you for a spin.

For a year I've been asking young folks about pornography's effect—and they've been honest. When I asked one successful 29-year-old last week if she feels porn influences her life, in bed or out, her answer was typical. "A thousand percent," she said. This woman finds herself repeatedly in porn-informed situations that are unpleasing, even unpleasant, while—crucially—her partner feels nothing's amiss. This isn't about one girl's luck or one guy's moves. It's about a generation of them. I've never felt so lucky to be over 40.

Today 12% of websites are pornographic, and 40 million Americans are regular visitors—including 70% of 18- to 34-year-olds, who look at porn at least once a month, according to a recent survey by Cosmopolitan magazine (which, let's face it, is the authority here). Fully 94% of therapists in another survey reported seeing an increase in people addicted to porn. It has become a whole generation's sex education and could be the same for the next—they are fumbling around online, not in the back seat. One estimate now puts the average age of first viewing at 11. Imagine seeing "Last Tango in Paris" before your first kiss.

Countless studies connect porn with a new and negative attitude to intimate relationships, and neurological imaging confirms it. Susan Fiske, professor of psychology at Princeton University, used MRI scans in 2010 to analyze men watching porn. Afterward, brain activity revealed, they looked at women more as objects than as people. The new DSM-5 will add the diagnosis "Hypersexual Disorder," which includes compulsive pornography use.