Operating characteristics of the vaginal photoplethysmograph: some implications for its use

Two operating characteristics of the vaginal photoplethysmograph were examined in an attempt to explain some of the methodological variance in the data produced by this device. Both the original Sintchak and Geer (1975) vaginal probe and a modified LED probe were examined for response consistency and temperature sensitivity. The results reveal that, for both types of probes, there is a considerable drift over time when the device is operated on DC in a temperature and light-controlled environment. This drift was not consistent across devices or trials, thus eliminating the possibility of experimentally or statistically controlling for it. In addition, both types of device were found to be extremely temperature sensitive when operated on DC in a light-controlled environment. Implications for continued use of the vaginal photoplethysmograph in research and clinical settings are discussed and recommendations are made regarding alternative genital measures of sexual arousal in women.