Validity and ethics of penile circumference measures of sexual arousal: a critical review

Wheeler and Rubin (1987) advanced evidence that penile volume responses (PVRs) were no more sensitive than penile circumference responses (PCRs) in measuring erection which the authors incorrectly identified with sexual arousal. Knowledge of the literature would have led them to question that identification and the methodology of their study. PVRs have repeatedly been demonstrated to assess validly not erection but the sexual orientation of individuals, when derived from the early stage of erectile response to brief stimuli that were from their onset of moderate erotic strength. PCR assessment has been of the degree of erection to stimuli of 2-10 min duration. No success has been reported using PCR measures of erection to classify subjects individually as to their sexual orientation. Classification of groups of 30 but not 6 homosexuals was successful using their PCRs to nudes. Attempts to identify rapists and pedophiles from normals, and aggressive from nonaggressive rapists and pedophiles by PCRs have failed to be replicated. In comparing PVRs and PCRs, Wheeler and Rubin used as stimuli three 10-min presentations of a film which apparently did not immediately introduce erotic material. This procedure would not elicit meaningful PVRs. Though never validated as a measure of individuals' sexual arousal, PCR measures of erection are currently widely recommended for assessment and determining treatment of individual sex offenders. If these assessments could affect or are believed by the offenders to affect the outcome of the legal processes in which they are involved, the procedure is not only scientifically unsupported, it is unethical.