The Vaginal Photoplethysmograph and Devices for Women: Gauging Female Arousal

Abstract

Researchers began to develop and to design machines for measuring women’s physiological changes during sexual arousal in the context of second-wave feminism in the late 1960s and early 1970s. A number of women-oriented machines were only used once or twice due to their painfulness, impracticality, or inability to provide quality data for analysis. Machines for women that have achieved stability in the research community include the vaginal photoplethysmograph (aka vagina photometer) and the labial thermistor. The vaginal photoplethysmograph measures vaginal blood volume (VBV) or vaginal pulse amplitude (VPA), depending on whether the researcher uses DC or AC current, respectively. Though the vaginal photoplethysmograph is currently the most popular instrument in studies of women’s sexualities, the fact that no one is sure what it measures or what those measurements indicate hampers its usefulness. In light of the problems associated with the vaginal photoplethysmograph, researchers often put it or other genital measurements together with non-genitally specific measurements such as blood pressure cuffs, respirators, and thermographs. Those combinations of machine-gathered data over the past four decades show that overall men’s subjective and physiological patterns of sexual arousal correlate much more often than do women’s patterns. Whether those gender differences are physiologically based or due to results from incomparable machines remains an open question.