Regression to the Mean Mimicking Changes in Sexual Arousal to Child Stimuli in Pedophiles

The sexual preference for prepubertal children (pedophilia) is generally assumed to be a lifelong condition. Müller et al. (2014) challenged the notion that pedophilia was stable. Using data from phallometric testing, they found that almost half of 40 adult pedophilic men did not show a corresponding arousal pattern at retest. Critics pointed out that regression to the mean and measurement error might account for these results. Müller et al. contested these explanations. The present study shows that regression to the mean in combination with low reliability does indeed provide an exhaustive explanation for the results. Using a statistical model and an estimate of the retest correlation derived from the data, the relative frequency of cases with an allegedly non-pedophilic arousal pattern was shown to be consistent with chance expectation. A bootstrap simulation showed that this outcome was to be expected under a wide range of retest correlations. A re-analysis of the original data from the study by Müller et al. corroborated the assumption of considerable measurement error. Therefore, the original data do not challenge the view that pedophilic sexual preference is stable.