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The Clitoral Photoplethysmograph: A Pilot Study Examining Discriminant and Convergent Validity
Kelly D Suschinsky1, Amanda J Shelley1, Jeroen Gerritsen2
1Department of Psychology, Queen's University, Kingston, ON, Canada.
Introduction:
The clitoral photoplethysmograph (CPP) is a relatively new device used to measure changes in clitoral blood volume (CBV); however, its construct validity has not yet been evaluated.
Aim:
To evaluate the discriminant and convergent validity of the CPP. For discriminant validity, CBV responses should differ between sexual and nonsexual emotional films if the CPP accurately assesses clitoral vasocongestion associated with sexual arousal; for convergent validity, CBV responses should significantly correlate with subjective reports of sexual arousal.
Methods:
Twenty women (M age = 21.2 years, SD = 3.4) watched neutral, anxiety-inducing, exhilarating, and sexual (female-male sex) audiovisual stimuli while their genital responses were measured simultaneously using vaginal and clitoral photoplethysmographs and CPPs. Most of these participants continuously reported sexual arousal throughout each stimulus (n = 16), and all reported their sexual and nonsexual affect before and after each stimulus; subjective responses were recorded via button presses using a keypad.
Main Outcome Measures:
Vaginal pulse amplitude (VPA), CBV, and self-reported sexual arousal and nonsexual affect were used as main outcome measures.
Results:
CBV demonstrated both discriminant and convergent validity. CBV responses were similar to VPA responses and self-reported sexual arousal; all responses differed significantly as a function of stimulus content, with the sexual stimulus eliciting greater relative changes than nonsexual stimuli. CBV, but not VPA, was significantly (negatively) correlated with continuous self-reported sexual arousal during the shorter sexual stimulus. CBV was significantly negatively correlated with VPA for the shorter sexual stimulus.
Conclusion:
CBV may be a valid measure of women's genital sexual arousal that provides complementary information to VPA and correlates with self-reported sexual arousal. Given our relatively small sample size, and that this is among the first research to use the CPP, the current findings must be replicated. More research using the CPP and other devices is required for a more comprehensive description of women's physiological sexual arousal.
