volunteer, without difference in erection patterns from the average population. One criticism of reoffending studies is that cultural attitudes that assume that men are sexually attracted to what they phallometrically respond to may cause men with no actual sexual interest in children to identify as pedophiles due to knowing that they phallometrically respond to them, making them more likely to be convicted again. Utility Erectile dysfunction The penile plethysmograph has value in screening organic versus psychogenic erectile dysfunction in urological polysomnography centres. Lack of sexual response during REM sleep may indicate that further evaluation by a urologist is required. When applied during nerve-sparing surgery, electrical stimulation penile plethysmograph is an erectile dysfunction prognostic. The patient is provided with objective information on his specific outcome which aids in planning for further erectile function therapies. Male homosexuality Phallometry may be able to distinguish gay men from heterosexual men. A phallometric study indicated that men who are more homophobic show greater penile arousal to stimuli depicting gay sex than do less homophobic men. Pedophilia, hebephilia, pedohebephilia, and ephebophilia Studies examining the efficiency of using penile plethysmograph to distinguish pedophilic men from non-pedophilic men, including hebephiles, show that a majority can be correctly assigned to the proper category. Sensitivity of a phallometric test is defined as the accuracy of the test to identify pedophilic (or hebephilic) individuals as having these sexual interests. Specificity of these tests is defined as the accuracy of the test to identify non-pedophilic (or non-hebephilic) individuals as such. Meta-analytic research has shown that sexual offenders against children show greater responding on phallometric tests for pedophilia and hebephilia than controls. Volumetric penile plethysmography In one study, 21% of the subjects were excluded for various reasons, including "the subject's erotic age-preference was uncertain and his phallometrically diagnosed sex-preference was the same as his verbal claim" and attempts to influence the outcome of the test. This study found the sensitivity for identifying pedohebephilia in sexual offenders against children admitting to this interest to be 100%. In addition, the sensitivity for this phallometric test in partially admitting sexual offenders against children was found to be 77% and for denying sexual offenders against children to be 58%. The specificity of this volumetric phallometric test for pedohebephilia was estimated to be 95%. Further studies by Freund have estimated the sensitivity of a volumetric test for pedohebephilia to be 35% for sexual offenders against children with a single female victim, 70% for those with two or more female victims, 77% for those offenders with one male victim, and 84% for those with two or more male victims. In this study, the specificity of the test was estimated to be 81% in community males and 97% in sexual offenders against adults. In a similar study, the sensitivity of a volumetric test for pedophilia to be 62% for sexual offenders against children with a single female victim, 90% for those with two or more female victims, 76% for those offenders with one male victim, and 95% for those with two or more male victims. In a separate study, sensitivity of the method to distinguish between pedohebephilic men from non-pedohebephilic men was estimated between 29% and 61% depending on subgroup. Specifically, sensitivity was estimated to be 61% for sexual offenders against children with 3 or more victims and 34% in incest offenders. The specificity of the test using a sample of sexual offenders against adults was 96% and the area under the curve for the test was estimated to be .86. Further research by this group found the specificity of this test to be 83% in a sample of non-offenders.