Control of penile tumescence: the effects of arousal level and stimulus content

The present study investigated the ability of incarcerated rapists to control penile tumescence at three different levels of arousal while viewing stimuli varying in content. Changes in penile tumescence were measured via mercury-in-rubber strain gauge plethysmography. Ss were presented attractive slide-transparencies of nude adult females and were instructed to allow themselves to become aroused. When the desired level of arousal for a particular trial was reached (25, 50 or 75% of full erection) the stimulus was removed and replaced with a second stimulus. These second stimuli belonged to one of four categories: (1) the same slide presented again; (2) a novel, but equally attractive slide of an adult female; (3) a blank slide; or (4) a slide of a nude prepubescent female. Ss were instructed to reduce their arousal as much as possible during this second stage while continuing to view the stimulus. Results indicate that control over penile tumescence is more difficult at low levels of arousal (25 and 50%) than at high levels (75%). It was also found that the content of the stimulus being viewed differentially affected the Ss' ability to control penile tumescence. The results are discussed with reference to current assessment techniques.