Vaginal pulse amplitude response patterns during erotic conditions and sleep.
Vaginal photoplethysmography has been used to investigate sexual arousal response patterns in small samples of sexually functional and dysfunctional women, but selection of subjects for these studies has not been of a standardized nature. In the present study, two groups of women, who placed in either the upper or lower percentile ranks on the Sexual Arousal Inventory (Hoon et al., 1976a), were compared on a physiological measure of sexual arousal, vaginal pulse amplitude (VPA), during both waking erotic conditions and sleep. As hypothesized, no differences in VPA were found between groups during either waking or sleeping conditions. Contrary to expectation, groups also did not differ on subjective ratings of their laboratory arousal. With both groups combined, differences in VPA levels were evident between baseline and erotic conditions. Similarly, VPA levels differed between stages of sleep, with highest levels observed during rapid-eye-movement (REM) sleep. These findings suggest that self-reported low arousability is not based on lack of physiological response and that retrospective, self-report measures of sexual arousability differ in important ways from subjective and physiological measures of sexual arousal in the laboratory. In order to adequately assess sexual arousability, future researchers must either devise laboratory conditions that more closely resemble erotic stimuli occurring in subjects' natural environments or validate physiological measures of arousal in nonlaboratory settings. Finally, the nocturnal evaluation of VPA seems potentially useful for cases in which organic factors may be contributing to sexual dysfunction.