Regression to the Mean or the Semmelweis Reflex?
We are delighted to have the opportunity to respond to a fourth critiqueofouroriginalstudy(Mulleretal.,2014) In thecurrent critique by Mokros and Harbermeyer (2015) they offer an essentially statistical argument based on a quasi statistical reanalysis of the raw data on which our study was based. They begin their article by referencing a study concerning flight cadets in which regression to the mean was used to explain the observation that cadets who performed poorly on the first training session were more likely to perform better on a second session than cadets who performed better on the first session (Kahneman,2012).This,ofcourse, isbecause theperformance of cadets on training sessions naturally changes. Since change is so common in the life sciences, we are surprised that the idea that sexual interest can change causes so much angst. One explanation may be the Semmelweis reflex, based on the apocryphal tale of how the medical establishment refused to accept Semmelweis' observation that hand washing was associated with decreased infant mortality on obstetrics wards (Sinclair, 1909).The Semmelweis reflex states there is tendency to reject new evidence if it appears to contradict the current paradigm. MokrosandHarbermeyer(2015)claimedthat''regression to the mean in combination with low reliability does indeed provide an exhaustive explanation for the results [of our study] We respectfully respond that invoking two phenomena (regressionto themean andreliability) to explainanobservation is not the same as refuting the alternative explanation, which is that sexual arousal patterns as measured by phallometry can change in the same way that the performance of cadets can change. Further, as we stated in our response to previous critics (Fedoroff et al. 2015) regression to the mean might explain a flattening out or averaging of phallometric test results but does not explain an increased response to adult stimuli by men who previously responded most to children. As we stated in the limitations section of our original article, phallometric testing has important limitationsandwecontinuetorecommendactual prospective replications of our study (we are currently conducting one ourselves that we hope will directly address the well founded concerns of our critics) We agree that reliability isan important issuethathasbeen inadequatelyaddressed in the literature on phallometry. Ideally, this would involve establishing equivalent stimulus sets that could be presented in a test retest study in which the time interval is short enough to exclude the possibility that the participant's interests have changed. Our group is hoping to accomplish both tasks in future work. We would like to emphasize some lessons to be learned from the Semmelweis story. In the case of Semmelweis, he simply observed an association and recommended a change in practice that followedfromanunprovenhypothesis: thathandwashing decreased infant deaths. Sadly, his recommendation was ignored, in part, because it preceded development of germ theory and contradicted the paradigms prevalent at the time that Semmelweis was practicing. In a similar vein, our group has presented data that can be explained in multiple ways, including the possibility that pedophilic sexual interest can decrease at the same time that adult interest increases. If true, it opens up new ways to research and treat people with pedophilia. If wrong, little harm can result from telling people with pedophilia there is evidence that pedophilia gets better, though some disagree. Conversely, the harm that may result from telling people with pedophilia there is no evidence they can recover is analogous to telling doctors there is no point in washing their hands. J. Paul Fedoroff Paul.Fedoroff@theroyal.ca
Archives of sexual behavior