SHE was a hitchhiker. He was a man away from home on business. The circumstances of the rape were only mildly contested in court and the jurors were in complete agreement on the ‘guilty’ verdict. There was, however, less agreement on what would constitute a fair sentence. As might be expected, women jurors were more severe than men; they suggested a sentence nearly 30 per cent longer. Less expected, and much more insidious, was the effect of pornography on their judgment: men who regularly watched pornographic videos suggested sentences half as long as those of other men.

Fortunately, this was not a real trial. The jurors were volunteers participating in a re-enactment of a rape trial to test the effects of exposing people to different amounts of pornography. This experiment is one of a growing number of studies which suggest that pornography changes the attitudes and behaviour of those who use it. And in the real world, these are not just a few dirty old men in raincoats.

Pornography is big business. So-called ‘top-shelf’ soft-porn magazines will sell over 20 million copies this year in Britain and will be read by about 5 million people. Several companies in Europe will secure multimillion-pound turnovers on pornographic magazines and videos – a business with an estimated worldwide value of several billion pounds. The ‘product’ in this vast business varies considerably and it caters for all tastes. At the extremes of hard-core pornography are sadomasochism, paedophilia and bestiality. In both American and Australian classifications of pornographic magazines, a quarter of all titles concerned some such form of sexual deviance. Less extreme hard-core pornography portrays petting, intercourse, oral sex and group sex. By far the most …