Assessing the effects of mass media is never simple, but the important questions about pornography are obvious: What happens when a culture is saturated with sexually explicit images eroticizing male domination and female subordination? When those images become increasingly cruel and degrading to women and increasingly racist? When pornography becomes the de facto sex education for most boys and an increasing number of girls?

These disturbing trends do not apply to all pornography. There are many varieties made by hundreds of small producers, but the porn industry around Los Angeles dominates, shaping cultural ideas about sexuality, relationships and intimacy. Just as the food industry shapes how we eat and the fashion industry shapes how we dress, the sex industry shapes the way we think about sex.

This dominant source of pornography has some consistent themes. The most extensive peer-reviewed study in the past decade found that a majority of scenes from 50 top-rented porn movies contained physical and verbal abuse of female performers. Physical aggression – including spanking, open-hand slapping and gagging – occurred in 88 percent of scenes, with expressions of verbal aggression – usually a man calling a woman derogatory names – in 48 percent.

Individual experiences as a viewer of pornography differ, and many men and some women report pleasurable experiences. But clear patterns emerge from more than 30 years of academic research and organizing informed by a feminist critique of pornography. In heterosexual couples, men who habitually use pornography sometimes withdraw from intimacy with female partners, and sometimes make demands on female partners for sexual acts that are uncomfortable, painful or degrading to the woman. Women in heterosexual relationships report that both these behaviors can destroy relationships, and men sometimes report that they are aware of the damage but cannot break the habit.

Anyone who doubts these trends should talk to marriage therapists and divorce lawyers.

Although there is little systematic research on performers, anecdotal evidence suggests it’s a harsh business for women. The industry portrays high-profile performers with glamorous lives, but producers and directors we’ve interviewed said candidly that the industry “chews up and spits out” women. According to the Adult Industry Medical Health Care Foundation, which provided testing and health care for performers in Los Angeles until it closed last year, female performers are at risk for injuries and diseases. The group’s founder once said the average career of these women was “six months to three years, tops,” after which they must cope with a variety of physical and psychological problems.

Pornography is the industrialization and commodification of sex, and like all big industries, its product is generic, formulaic and plasticized. These images tend to rob sex of its creativity, playfulness and intimacy, and hence are ultimately profoundly alienating. The performers, the consumers and the culture deserve better.