Research concerning the effects of pornography is inconclusive on the issue of crime. Some studies support the contention that the viewing of pornographic material may increase rates of sexual crimes, while others have shown no effects, or indeed even a decrease in the rates of such crimes.
An epidemiological study describes the association between given behaviours or environmental conditions, and physical or psychological health by means of observation of real-world phenomena through statistical data. In other words: the relation between behaviour and psyche. Epidemiological studies generally have high levels of external validity, insofar as they accurately describe events as they occur outside of a laboratory setting, but low levels of internal validity, since they do not strongly establish cause-and-effect relationships between the behaviours or conditions under study, and the health consequences observed.
In 1970, the studies on pornography and sex crimes in Denmark by the Danish criminologist Berl Kutchinsky found that the legalizing of pornography in Denmark had not – as the researchers expected – resulted in an increase of sex crimes.
This result presents a stark contrast to the 1986 review of epidemiological studies by Neil M. Malamuth who found that the quantity of pornographic material viewed by men was positively correlated with degree to which they endorsed sexual assault. Malamuth’s work describes a diverse sample of Canadian men that the more exposure to pornography led to higher acceptance of rape myths, violence against women, and general sexual callousness.
On the other hand, the failure to find a statistically significant correlation led Malamuth to examine other interesting correlations, which took into account the information about sexual (direct or indirect) contact the samples obtained in their childhood. Here, pornography emerged as the second most important source of information.
In a 1965 paper called Sexual Deviation as Conditioned Behavior: A Hypothesis, R.J. McGuire found that the viewing of pornography can serve as a source of a paraphilic so-called vivid sexual fantasy which, when contemplated during masturbation, may condition men into perversion.
But in conclusion, the relations between these private acts and sexually related acts of crime are still inconclusive because of the valid laboratory researched evidence on both side of the argument. Experimental results are not immediately reliable outside the controlled environment.