Plethysmographic Assessment of Incarcerated Nonsexual Offenders: A Comparison with Rapists

Abstract

Plethysmographic testing was completed on 100 research participants from the same medium-security prison population, 50 of whom were incarcerated for nonsexual offenses. In order to strengthen the validity of the research, only participants who achieved full arousal were included in the sample, and the percentage of full erection scores, as well as the Rape Index, were examined. The resulting sexual arousal profiles revealed striking similarities between rapists and control participants, indicating that deviant arousal alone did not distinguish these sexual offenders from nonsexual offenders. The only marked difference between the two groups was in the almost-perfect ability of control participants to inhibit deviant arousal and the weak ability of sexual offenders to accomplish this. The suggestion was advanced that a determination of an offender's ability to inhibit deviant arousal may be the only aspect of plethysmographic testing which has practical application in the assessment of rapists.

Sexual Arousal as a Function of Stimulus Mode: Implications for Phallometric Assessment

“…A similar conclusion was earlier advanced by Howes [18] in a study which compared the sexual arousal profiles of 50 incarcerated sexual offenders with 50 incarcerated non-sexual offenders [18].…”

“…Citing more recent studies such as Hanson and Morton-Bourgon's meta-analytic research which also indicated that deviant arousal to children is related to higher risk of reoffending against children [17], Wilson et al commented, "Perhaps the best means of objectively measuring deviant sexual interest is the phallometric test" [7]. Greater arousal to depictions of coercive sex has been observed in convicted rapists [13,18], and although Wilson et al identified concerns about a lack of standardization they nonetheless observed that "many practitioners continue to view phallometry as a reliable means of assessing deviant sexual interests. "…”

The phallometric assessment of sex offenders: an update

“…For instance, following the methodology recommended by Lalumiere and Quinsey (1993), Barsetti et al (1998), in the study previously reviewed, set the specificity level to minimize the number of false positives at 95% so that only 5% of the non-offenders are wrongly identified as deviant, and reported a resultant sensitivity of 68.4 for intra-familial offenders and 65% for extra-familial offenders so that overall the proportion of misclassified offenders is around 33%. Howes (1998) noted that setting the rape index at 1 led to 23% of his rapist sample being correctly identified and 6% of the controls misclassified whereas when setting the index at 0.7, 53% of rapist were correctly identified and 30% of the controls were misclassified.…”

“…; this is following evidence from Hart and Willmott (1994), who demonstrated that presenting pictures in groups was more discriminatory than presenting them singly. The stimuli are open to criticism for not including neutral scenes (Quinsey and Lalumiere, 1996), or conditions when subjects are asked to suppress their arousal (Howes 1995(Howes , 1998, or enough exemplars of each condition and because the MAR videotape is not explicitly sexual or brutally violent (Harris et al, 1992;Fedora et al, 1992;Lalumiere and Quinsey, 1994) but it has the advantage of being ethically defensible and its consistent use over seven sites means that by the year 2000 a database of over 500 cases will be available to carry out validity/reliability studies.…”

The Utility of the Diagnosis of Pedophilia: A Comparison of Various Classification Procedures

“…For example, numerous studies have demonstrated that a significant proportion of offenders are able to suppress penile responses (Howes, 1998;Kalmus & Beech, 2005;Marshall & Fernandez, 2000). Furthermore, the interpretation of arousal is difficult, as some offenders may not be aroused to a certain stimulus, while others may be aroused to deviant stimuli but are not known to be sexual offenders (Bahroo, 2003).…”