Penile Plethysmograph Stimulus Sets

Does Use of Age and Gender Appropriate Voices Affect Arousal to Child Victim Scenarios?

The sexual abuse of children is a major public health problem. The identification and treatment of offenders against children and potential offenders against children is an area of important research. In North America, estimated sexual offenses number more than 100,000 annually (USDOJ, 2006). Most reported offenses involve men assaulting children. Many sex offenders show deviant (abnormal) sexual arousal patterns. Penile plethysmography (PPG) is the “gold standard” for objective measurement of sexual arousal in men (Fedoroff et. al., 2009). PPG consists of presenting a variety of test stimuli to the person being tested. During PPG, electronic measurements are made in any changes in the person’s penile circumference. It is assumed that increases in penis diameter after presentation of a test stimulus reflect the degree of sexual arousal that the stimulus elicits. Despite the widespread use and published research on the reliability and validity of PPG, there is still lack of universal standard for assessment or subsequent analysis of response to treatment. One reason for the lack of standardization is the fact that different labs use different stimulus sets. For example, in the United States only auditory stimuli are used, while in Canada there is greater reliance on visual stimulus sets. The primary aim of this study is to establish the efficacy of a novel stimulus set that will be acceptable for use in both the United States and Canada. A secondary aim is to compare the efficacy of age and gender congruent auditory stimulus sets to the stimulus set that does not have these characteristics.

Stimuli sets can be visual, auditory or both. In Canada PPG stimulus sets are a combination of audio depictions of sexual encounters paired with non-sexual photographs of age congruent nude males or females. In the United States, the federal government made it illegal to possess photographs of nude persons under the age of eighteen even for clinical, forensic or research purposes. As a result, all the stimulus sets in the United States are strictly audio or audio with non-nude photos. In Canada, nude pictures are still legal for these purposes and are used routinely. The audio depictions in both the United States and Canada have historically used adult male voices speaking in a monotone voice to describe a variety of legal and illegal sexual scenarios.

The Sexual Behaviors Evaluation, Research and Treatment Clinic and Laboratory at the University of South Carolina School of Medicine used the Marshall audio set in the past and have recently developed a stimuli set using age and gender-congruent voices known as the Real Child Voices (RCV) set. The Sexual Behaviours Clinic (SBC) at the Royal Ottawa Mental Health Care proposes to compare the RCV stimuli with our current stimuli set (SBC stimuli). The SBC has used an independent set of audio-taped stimuli and a set of nude slides for more than 20 years. Although our assessment procedures have good sensitivity and specificity, responses to auditory stimuli using an adult voice and auditory stimuli using an age and gender congruent child’s voice have never been directly compared in a scientific protocol.

The study participants will be adult SBC out-patients (PATIENTS) who sought treatment for sexual problems involving children and healthy male controls (CONTROLS) who have no known sexual interest in children and no history of sex offenses. Both groups of participants (PATIENTS and CONTROLS) will be tested in the SBC PPG lab with the Real Child Voices (RCV) set and the SBC audio and nude slides. Each participant will be tested using both stimulus sets (RCV and SBC stimuli) but the order of presentation of the RCV or SBC stimulus sets will be randomized. This study will provide empirical data concerning whether the RCV stimulus set is as sensitive and specific as the SBC stimulus set.

Data from this study will be of immediate benefit for the SBC since it will assist in validating current and novel assessment paradigm and potential measures of treatment efficacy. Information about the effect of age and gender congruence on auditory stimuli will also be of use in the elucidation of a more sophisticated explanation of why some men have engaged in harmful sexual behaviors. This study will improve the ability of mental health practitioners to evaluate and treat persons with sexually aggressive offending, and problematic sexual behaviours, and aid those responsible for the determination of appropriate treatment settings and risk appraisal.

Investigators: Jonathan Gray, Paul Fedoroff, Susan Curry

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