Volunteer bias in sex research: effects of variable stimuli content and intrusiveness of measurement

Previous studies of volunteer bias in sex research found that volunteers for such studies differed from nonâ volunteers in terms of reporting increased heterosexual experience; more liberal attitudes toward sex; increased exposure to commercialized erotica; and an increase in sexual trauma. The object of this study was to investigate the effects that varying the stimuli content (i.e. heterosexual vs gay male vs lesbian) of films used in sexual arousal studies would have on volunteer rate and characteristics of the volunteers. Also investigated was the effect of varying intrusiveness of measurement (physiological vs subjective measures) and the interaction of film and measurement type. 285 female and male undergraduates volunteered for a questionnaire study of sexuality. Demographics, heterosexual and homosexual behavior, exposure to pornography, attitudes toward sexuality and homosexuality and oneâ s position on a sexâ role continuum were assessed. Subjects were provided with a complete written description of a further study of sexual arousal, utilizing sexually explicit films, in which the stimuli content and the intrusiveness of measurement the subject would experience were randomly varied. Previous findings regarding volunteers were replicated except for reporting of sexual trauma. Volunteers reported more sexual fantasies with both heterosexual and homosexual themes. They scored higher on sensation seeking and experience seeking. No conclusions could be drawn regarding impact of sexual preference or homosexual activities due to the limited reporting of such behaviors. No significant effects were found for intrusiveness of measurement. Pseudo-volunteers for the arousal study were found to be significantly different from non-volunteers on several variables. This resulted in questioning the classification of pseudoâ volunteers with nonâ volunteers. Possible directions for future research are presented.