Penis Size and Magnitude of Erectile Change as Spurious Factors in Estimating Sexual Arousal

Abstract

Differences in penis size or in the magnitude of change in penis size to full erection can be confounding factors in phallometric assessment of erotic preference. This paper reviews this issue and studies the effect of penis size and magnitude of change in penis size on decisions which might be made in the assessment and treatment of sex offenders. Various techniques for attempting to correct for individual differences are discussed, including the use of percentage of full erection scores, relative arousal scores, and ipsative z-scores. Two studies were undertaken to improve estimates of percentage of full erection scores. In one of these studies normative data on penile circumference in the flaccid state was used to predict full erection. In the other study, self measurements of penis size were used. Results indicated that predictions of full erection from flaccid state may be useful. Self measurements were not found to be useful. Suggestions are made which may minimize the effect of individual differences in penis size in phallometric assessment.