Sexual Abuse: A Journal of Research and Treatment [saj] pp916-sebu-469147 July 16, 2003 14:2 Style ﬁle version Nov 28th, 2002
Sexual Abuse: A Journal of Research and Treatment, Vol. 15, No. 4, October 2003 (
Circumferential Change Scores in Phallometric
Assessment: Normative Data
Richard J. Howes
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 erec-
tion) 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 appli-
cation of the principles of science will the procedure of phallometric assessment
fulﬁll its true potential.
KEY WORDS: penile plethysmograph; phallometry; sexual arousal interpretation; sexual offender
assessment; phallometric testing.
Many researchers have endorsed the view that the procedure of phallometric
assessment has demonstrated both validity and a considerable potential for clini-
cal application (Earls, 1983; Howes, 1995; McAnulty & Adams, 1992; McGrath,
1992; Murphy & Barbaree, 1994; Quinsey, Lalumiere, Rice, & Harris, 1995;
Simon &Shouten, 1991; Williams, 1995).Penile tumescencehas beendescribed as
the most sensitive index of sexual arousal and the most reliable of the physiological
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