Circumferential change scores in phallometric assessment: normative data.

Phallometric testing is a procedure that has enjoyed considerable popularity as an objective component in the assessment of sexual offenders. The value of this procedure may be most notably compromised in the realm of interpretation, and problems in interpretation are particularly acute for those participants where full arousal is not obtained during testing. The calculation of Percent Full Erection (PFE) scores has of necessity involved a speculative component in such cases. Eliminating this speculation through empirical investigation was the purpose of the current research. Circumferential change scores (from flaccidity to full erection) were obtained for 724 respondents at nine North American correctional facilities, allowing for the calculation of descriptive statistics and a determination of the distribution characteristics of these scores. The results provide an empirical basis for calculating PFE scores and interpreting phallometric data in those cases where full arousal is not obtained, and specific confidence levels associated with interpretation are offered. It is suggested that only through a more rigorous application of the principles of science will the procedure of phallometric assessment fulfill its true potential.