Discriminative and Predictive Validity of the Penile Plethysmograph in Adolescent Sex Offenders

The current study addresses the discriminative and predictive validity of the penile plethysmograph (PPG) in a sample of 132 male adolescent sex offenders who were admitted to a sex offender treatment program. The subjects were assessed pretreatment and posttreatment, under two different instructions sets: an Arouse condition, where subjects allowed themselves to become aroused; and a Suppress condition, where subjects attempted to suppress or control their arousal. Under the pretreatment Arouse condition, the group with male child victims demonstrated significantly greater arousal to child stimuli than the group with female nonchild victims. However, the group with female child victims could not be differentiated from the group with female nonchild victims. Under the Suppress condition, there was no evidence of discriminative validity for any of the PPG indices. As for predictive validity, posttreatment arousal to male and female children was significantly related to sexual offense recidivism. Posttreatment inability to suppress deviant arousal to male and female children was also significantly related to sexual offense recidivism over the 6-year follow-up period. In light of these findings, the implications for adolescent sex offender research and treatment are discussed.