306 Is stranger rape a strategy to avoid female courtship behavior?: a parallel fMRI and penile plethysmography study

Abstract

The absence of pleasant and friendly interaction with a woman prior to attack is a typical feature of stranger rape. This might indicate several mechanisms – the impulsivity of a perpetrator (cannot control their sex drive), the preference for humiliation and control (sadistic-like motivation) or their inability to achieve satisfactory sexual satisfaction in the context of normal female courtship behavior. Given that there is empirical evidence against first two possibilities (Harris et al., 2012; Seto et al., 2012), we tested the third possibility. We hypothesized that genital display of a female preceded by courtship behavior will create lesser penile reaction and lesser brain activation in rapists as opposed to controls, while the ratio will be reversed for the naked female displaying her genitalia preceded by non-courtship-like behaviors. The sample consisted of 15 convicted male rapists (diagnosed mainly as F65.9 “disorder of sexual preference not otherwise specified” in ICD-11) and 15 control males matched for demographic characteristics. Participants were exposed to the set of still pictures representing following conditions: 1) genital display preceded by courtship-like facial expressions, 2) genital display preceded by lustful facial expressions, 3) genital display preceded by facial expressions of distress, 4) genital display preceded by pictures of nature (control condition). Duration of each set of stimuli (a unit of analysis) was 18 seconds. The experiment lasted 36 minutes in total. Stimuli were presented in pseudo-random order. During the experiment, we simultaneously measured sexual arousal and brain response, using custom-built volumetric penile plethysmography (Heinrich SOM) and 3 Tesla magnetic resonance device, respectively. Other related variables (e.g. frequencies of solitary and dyadic sexual activities, sexual fantasies, ability for attachment and romantic love and specifics of courtship behavior) were assessed using questionnaires and anamnestic interview. SPSS 20 and SPM 12 software (MATLAB-associated) were used for data analysis.