Judgment of age and attractiveness in a paired comparison task: Testing a picture set developed for diagnosing paedophilia

Purpose. The Not-Real-People picture set serves as stimulus material for assessing paedophilic sexual interest. The pictures were generated according to five stages of sexual maturation from infancy to adulthood. While experts seem to be able to discern between the pictures based on maturity levels for a nude variant of the stimuli, it remained unclear whether lay persons would be able to reliably distinguish between picture of clothed individuals from various maturity levels. Methods. Heterosexual university students (52 females, 50 males) participated in a paired comparison task, deciding which of the persons shown on two pictures was younger and which one was more attractive. Additionally, reaction times were recorded. Results. Both male and female judges were able to differentiate between stimuli from the opposite sex with regard to age: the perception of the stages of pubertal development conformed to a measurement on a ratio scale. Similarly, the decisions on attractiveness of the categories were in accordance with a ratio scale. Male participants favoured adolescent and adult female stimuli. Contrary to expectation, female participants did not show a preference for any single age category. Conclusions. The stimuli appear suitable for diagnostic purposes. The participants’ decisions reflect the inherent maturity levels of the persons depicted. Reaction times in the paired comparison paradigm increase with task difficulty (i.e., similitude of pictures). The implications for indirect measures of sexual interest, based on reaction times, are discussed