Procedure
Upon entering the laboratory, participants were asked to read an information letter, explaining that the study was intended to measure the effect of sexual arousal and alcohol on working memory, reaction times to computer tests and condomless sex. Then, they were asked to sign an informed consent statement. Subsequently, it was checked whether they were sober using the AlcoTrue CThree drinks were them consumed. One minute after participants finished their third drink another breathalyzer test was administered, to assure there was no lingering alcohol present in participants’ saliva that could confound the measurement. Next, they were verbally instructed how to apply the penile plethysmograph, then privately applied the plethysmograph. Next, a baseline penile circumference measurement was performed. Subsequently, participants rated their level of subjective sexual arousal, their subjective level of intoxication, and how many of the drinks they had consumed they believed contained alcohol.After all baseline measures were completed, participants viewed a five-minute video clip that was either erotic or neutral in nature. They wore headphones to hear the sound of the movie clip while watching the video on screen. After they watched this video, without any further instruction participants were asked to complete measures of explicit attitudes, risk perception, and intentions. Next, the n-back task was administered on screen while participants still could hear the audio from the video clip through the headphones but were not shown the visual content. This was done in order to try and maintain sexual arousal during the working memory task (Geer & Fuhr, After participants had completed one condition (erotic or neutral), they were given a break to wash out any carry-over effects from the sexual arousal manipulation. During this ten-minute break, they were asked to play some casual games on a tablet computer. The sexual arousal washout period has been used before in within-subjects designs of studies into sexual arousal effects on condom use intentions (e.g., Wolfs et al., Participants were asked to return to the laboratory for a second session exactly one week later (same day of the week and same hour). This second session was identical to the first one with the exception that there were no baseline measurements at the beginning of the session and that participants were assigned to the opposite beverage conditions in the second session. The order of beverage condition and sexual arousal condition was counterbalanced between participants.This protocol was approved by the medical ethical committee of the Zuyderland Hospital in Heerlen, the Netherlands, and by the Ethics Review Committee Psychology and Neuroscience at Maastricht University, the Netherlands.