Rape to exert power and control?

Found via the German "Alles Evolution" blog. Thx:

The effect of conjugal visitation on sexual violence in prison - D'Alessio SJ et al - 2012

At present, there are two opposing theories of the causes of sexual violence. The feminist perspective asserts that sexual violence is motivated primarily by an offender’s desire to exert power and control over another individual. Therefore, according to this theory, conjugal visitation should have little or no effect on sexual offending in prison. In contrast, sexual gratification theory argues that the ultimate motivation for rape and sexual violence is to achieve sexual gratification. Therefore, based on this view, conjugal visitation should reduce sexual offending in prison.[...]

After taking into account the size of the prison population*, the researchers found that the rate of sexual violence was significantly lower in states that allowed conjugal visitation: 57 incidents per 100,000 inmates compared with 226 incidents per 100,000 inmates in states that do not allow the practice. This finding casts doubt on the feminist perspective and supports sexual gratification theory