Does pornography breed rape? Do violent movies breed violent crime? Quite the opposite, it seems.
First, porn. What happens when more people view more of it? The rise of the Internet offers a gigantic natural experiment. Better yet, because Internet usage caught on at different times in different states, it offers 50 natural experiments.
The bottom line on these experiments is, "More Net access, less rape." A 10 percent increase in Net access yields about a 7.3 percent decrease in reported rapes. States that adopted the Internet quickly saw the biggest declines. And, according to Clemson professor Todd Kendall, the effects remain even after you control for all of the obvious confounding variables, such as alcohol consumption, police presence, poverty and unemployment rates, population density, and so forth.
OK, so we can at least tentatively conclude that Net access reduces rape. But that's a far cry from proving that porn access reduces rape. Maybe rape is down because the rapists are all indoors reading Slate or vandalizing Wikipedia. But professor Kendall points out that there is no similar effect of Internet access on homicide. It's hard to see how Wikipedia can deter rape without deterring other violent crimes at the same time. On the other hand, it's easy to imagine how porn might serve as a substitute for rape.
If not Wikipedia, then what? Maybe rape is down because former rapists have found their true loves on Match.com. But professor Kendall points out that the effects are strongest among 15-year-old to 19-year-old perpetrators—the group least likely to use such dating services.
Moreover, professor Kendall argues that those teenagers are precisely the group that (presumably) relies most heavily on the Internet for access to porn. When you're living with your parents, it's a lot easier to close your browser in a hurry than to hide a stash of magazines. So, the auxiliary evidence is all consistent with the hypothesis that Net access reduces rape because Net access makes it easy to find porn.
Next, violence. What happens when a particularly violent movie is released? Answer: Violent crime rates fall. Instantly. Here again, we have a lot of natural experiments: The number of violent movie releases changes a lot from week to week. One weekend, 12 million people watch Hannibal, and another weekend, 12 million watch Wallace & Gromit: The Curse of the Were-Rabbit.
University of California professors Gordon Dahl and Stefano DellaVigna compared what happens on those weekends. The bottom line: More violence on the screen means less violence in the streets. Probably that's because violent criminals prefer violent movies, and as long as they're at the movies, they're not out causing mischief. They'd rather see Hannibal than rob you, but they'd rather rob you than sit through Wallace & Gromit.
I say that's the most probable explanation, because the biggest drop in crime (about a 2 percent drop for every million people watching violent movies) occurs between 6 p.m. and midnight—the prime moviegoing hours. And what happens when the theaters close? Answer: Crime stays down, though not by quite as much. Dahl and DellaVigna speculate that this is because two hours at the movies means two hours of drinking Coke instead of beer, with sobering effects that persist right on through till morning. Speaking of morning, after 6 a.m., crime returns to its original level.
What about those experiments you learned about in freshman psych, where subjects exposed to violent images were more willing to turn up the voltage on actors who they believed were receiving painful electric shocks? Those experiments demonstrate, perhaps, that most people become more violent after viewing violent images. But that's the wrong question here. The right question is: Do the sort of people who commit violent crimes commit more crimes when they watch violence? And the answer appears to be no, for the simple reason that they can't commit crimes and watch movies simultaneously.