A Test of Three Different Explanations for Low Stimulus Response Discrimination in Phallometric Testing

Abstract

ABSTRACT Phallometric assessment is used to assess men’s sexual interest in children and to assist in risk assessment and treatment planning. A common response pattern, especially when the assessment is conducted in a forensic context, is an indiscriminate pattern of penile responses: No sexual stimulus seems to produce a substantially higher response than another. This indiscriminate response profile could be the result of (1) faking good (in particular, reducing the responses to child stimuli); (2) floor or ceiling effects caused by low or high arousability, or (3) non-exclusivity (the individual is similarly sexually interested in both children and adults). In this study of 2,858 adult male patients who underwent volumetric phallometric assessment for sexual interest in children between 1995 and 2011, we tested these three possible explanations. Results showed support for each of the explanations, but the variance accounted for in response discrimination was quite small when considering each explanation (separately or when considered together). We discuss avenues for future research to better discern the causes of indiscriminate responding in phallometric assessment.