The differentiation of francophone rapists and non-rapists using penile circumferential measures

Since 1977 there have been seven published and two unpublished reports concerning the differentiation of rapists and non-rapists using penile circumferential measures. Of the published experiments, six report significant differences between groups. The purpose of the present investigation was to extend the scope of this work using a French-speaking population. Ten rapists and ten non-rapists were exposed to four classes of audiotaped stimuli: mutually consenting, rape, aggressive and sexually neutral episodes. Penile circumference changes were recorded during stimulus presentation. The results indicated that while rapist and non-rapist groups were not distinguished in terms to their response to mutually consenting sex, the two groups were distinguished with respect to their responses to rape episodes. The discrimination was even more marked when the results were individually analyzed using the rape index. Thus we were able to validate, in French-speaking subjects, the differentiation between rapists and non-rapists using penile measures. Several hypotheses are advanced which could explain the differences between experiments which demonstrate and those which fail to demonstrate discrimination between groups.