A failure to demonstrate changes in sexual interest in pedophilic men: comment on Müller et Al. (2014).

Abstract

Muller et al. (2014) presented data representing test–retest results from penile plethysmography testing (PPT) among 43 men diagnosed with pedophilia. They claimed to have found evidence for impressive change in PPT-measured preferences for child versus adult stimuli and asserted that ‘‘this represents a significant challenge to the hypothesis that sexual interest in men with pedophilia is unchangeable.’’ Although it would be both newsworthy and uplifting if Muller et al. had indeed shown that meaningful changes in such preferences occurred among pedophilic men, unfortunately the data presented by Muller et al. do not come close to establishing this. In this critique, I explain why the data by Muller et al. fail to show meaningful changes in PPT-measured arousal patterns. The main concern is this: PPT arousal patterns have measurement error (and there are indications that the data of Muller et al. include substantial measurement error). Thus, to show that a man’s change in PPT indices is meaningful, one must demonstrate that the change does not simply reflect measurement error, a necessary step that Muller et al. did not even attempt. I suggest some ways of accomplishing this in future research.