This chapter focuses on the laboratory measurement of penile response in the assessment of sexual arousal. Changes in penile tumescence, as measured by penile plethysmography (PPG), is a widely recognized means of measuring male sexual arousal in response to the presentation of various stimuli. Although not part of the
Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) or International Classification of Diseases (ICD) criteria for any paraphilias, PPG is widely considered by researchers and clinicians to be an important contributor in the assessment and treatment of males with paraphilic interests and/or males who have committed sex crimes. PPG, also referred to as phallometry, phallometrics, or penile tumescence testing (PTT), contributes to clinical assessment of paraphilic interests, appraisal of risk of recidivism, and provides an objective measurement of changes in sexual arousal in response to treatment. Before the development of PPG techniques, clinicians assessing individuals to learn their sexual arousal patterns relied primarily on self-report for the evaluation of treatment needs and outcomes.