Some fear that users of online porn who start with vanilla fare will click through to more outré stuff and develop a taste for it. This could, conceivably, be a danger for adolescents. But adults’ tastes seem to be pretty fixed—and quite mundane. Mr Ogas and Mr Gaddam discovered that most of those searching for pornography have just one or two stable interests (body parts, sexual practices, performers’ characteristics and so on). During the three months covered by the AOL data, 56% of those who searched for porn used terms in just one category. The average number of categories was two. Less than 1% searched for terms in ten categories or more. The top four categories were words relating to youth, breasts, vaginas and buttocks. The modal online sexual interest of a heterosexual male is “busty teen” or a variant, says Mr Ogas. “Men don’t start searching for big breasts and work up to bestiality.”

That is reassuring, as far as it goes. But even if porn usage does not change viewers’ tastes, could it be affecting bedroom etiquette? In a study published last year, researchers at London University sought to find out whether porn played a part in young people’s decisions to have anal sex. They interviewed 130 16- to 18-year-olds, some in groups and some alone. Both sexes regarded it as likely to be pleasurable for men but painful for women, at least if they were “uptight” or “naive”. Many of the young men described pressing girlfriends to consent; young women said they continued to be asked, sometimes forcefully, even after repeated refusals.

The participants said that porn “made” men want anal sex—an explanation Cicely Marston, one of the researchers, describes as “partial, at best”. The desire evinced by many young men to boast of sexual conquests seemed to be at least as influential. But porn’s influence was evident in their understanding of sex more generally. The researchers asked them to name all the sexual practices they knew of. They listed many porn tropes, such as threesomes and gang bangs, and some scatological and extremely violent acts made notorious by particular clips and films.