The Empirical Status of the Preparation Hypothesis: Explicating Women's Genital Responses to Sexual Stimuli in the Laboratory.

Research conducted in our laboratory and in other laboratories has revealed that (1) women's genital responses to visual and auditory stimuli are strongly affected by the presence of sexual cues, but that (2) specific sexual cues (e.g., gender of actors, the presence of sexual violence) often have little impact on the magnitude of the responses-that is, similar genital responses are observed to very different sexual stimuli. In addition, (3) women's genital responses do not strongly correspond with self-reported sexual partner and activity preferences, or (4) with self-reported sexual arousal during the presentation of sexual stimuli. Taken together, these facts represent a puzzle, especially considering that men's genital responses are highly affected by specific sexual cues and strongly correspond to stated preferences and self-reported sexual arousal. One hypothesis to explain female low cue-specificity and low concordance (relative to men) is the preparation hypothesis: Women's indiscriminate genital responses serve a protective function. That is, they do not indicate or necessarily promote sexual interest and motivation, but rather prepare the vaginal lumen for possible sexual activity and therefore prevent injuries that may occur as a result of penetration. We review evidence for and against this hypothesis. We conclude that the evidence is favorable but not entirely convincing, and more work is required to reach a firm conclusion. We offer directions for future research.

Can the Vaginal Photoplethysmograph and Its Associated Methodology Be Used to Assess Anal Vasocongestion in Women and Men?

Forty years ago, researchers documented changes in vascular and muscular activity within the anal canal of women and men who engaged in sexual self-stimulation. Vascular changes were assessed using a photoplethysmograph that aimed to detect changes in pelvic vasocongestion. An important advantage of detecting sexual response within the anal canal is that the device, its anatomical placement, and the data output are identical for women and men, therefore facilitating gender comparisons of response patterns. In this study, the vaginal photoplethysmograph (VPP), the most common measure of genital response in women, was administered intra-anally as an anal photoplethysmograph (APG) to examine its validity and sensitivity as an indicator of sexual response. The final sample comprised 20 women and 20 men who were exposed to 12, 90-s sexual and nonsexual film clips while their APG responses were recorded. Participants also rated their sexual arousal and affective responses to the stimuli. There was evidence that APG responses were specific to sexual stimuli and were sensitive to erotic intensity in women. The degree of discrimination between sexual and nonsexual stimuli was lower in men. Unlike most sexual psychophysiological studies, the positive correlation between physiological and self-reported sexual arousal was stronger in women than in men. There was a relatively high number of data artifacts and the waveform morphology was uncharacteristic of that typically observed with VPP. The potential role of anal musculature interference on the APG signal is discussed, as well as avenues for future research.

Effect of a Condom Cover on Vaginal Photoplethysmographic Responses.

INTRODUCTION: The vaginal photoplethysmograph (VPP) is a reusable intravaginal device often employed in sexual psychophysiology studies to assess changes in vaginal blood flow, an indicator of sexual arousal. AIM: To test whether placing a disposable cover on the VPP probe impacts the acquired data. A condom cover would reduce risk of disease transmission and likely increase participant comfort but may negatively impact the VPP signal. METHOD: The genital responses of 25 cisgender women (mean age = 21.3 years, standard deviation = 2.6) were assessed with VPP in a within-subjects design with 2 conditions-with and without a polyisoprene condom cover. Sexual responses were elicited by audiovisual film clips that varied in erotic intensity: nonsexual (nonsexual male-female interaction), low-intensity sexual (nude exercise), and high-intensity sexual (male-female intercourse). Women continuously rated their sexual arousal during stimulus presentations. MAIN OUTCOME MEASURE: Change in vaginal pulse amplitude and also self-reported sexual arousal. RESULTS: The magnitude of sexual response to each stimulus category and the overall pattern of results were found to be highly similar in the cover-off and cover-on conditions. The high-intensity sexual stimulus category elicited a greater sexual response than all other categories. The low-intensity sexual category elicited a (small) genital response in only the cover-on condition, although we suspect this is a spurious finding. There was no difference in the average number of edited movement artifacts across conditions. CLINICAL IMPLICATIONS: Potential benefits of encasing the VPP probe with a protective cover include enhanced participant safety and comfort, especially if assessing genital responses of high-risk or immunocompromised samples. The use of a cover complies with current guidelines for reprocessing semi-critical medical devices (eg, vaginal ultrasound probes) in many regions. STRENGTHS & LIMITATIONS: Although the idea of a VPP probe cover had been discussed among sexual psychophysiology researchers, this is the first study to empirically test whether a cover could jeopardize VPP data. Potential limitations include the use of a 10-Hz VPP sampling rate and a cover that was not tailored to the size of the VPP probe. CONCLUSION: Placing a protective cover on the VPP probe did not appear to meaningfully impact sexual arousal or the VPP data. Based on these results and the potential advantages of a protective cover, researchers may wish to integrate the use a condom cover in their experiment protocols and clinical applications. Sawatsky ML, Lalumière ML. Effect of a Condom Cover on Vaginal Photoplethysmographic Responses. J Sex Med 2020; 17:702-715.

Genital lubrication: A cue-specific sexual response?

Women's genital responses are sensitive to the presence and intensity of sexual cues, yet some stimulus features (e.g., male vs. female actors, consensual vs. non-consensual interactions) have little influence on the magnitude of response-a phenomenon called low cue-specificity. Genital responses are typically assessed using vaginal photoplethysmography, a measure of vaginal vasocongestion, itself a precursor to lubrication. One explanation for low cue-specificity is the preparation hypothesis: Women genitally respond to almost all sexual cues because lubrication functions to protect genital organs from potential injury should vaginal penetration occur. In order to test the preparation hypothesis, both vaginal vasocongestion and introital lubrication were assessed in a sample of 20 women in response to sexually explicit films. While patterns of vasocongestion were consistent with low cue-specificity for gender cues and type of sexual activity, lubrication was specific to women's most preferred sexual stimulus categories. These results are inconsistent with the preparation hypothesis.

Consensual Victim-Perpetrator Intercourse after Nonconsensual Sex: The Impact of Prior Relationship.

Some female victims of nonconsensual sex subsequently have consensual sexual intercourse with the perpetrator and are more likely to do so if intercourse occurred during the nonconsensual sex than if it did not. Some evolutionary psychologists have postulated that there is something significant about nonconsensual intercourse that causes women to subsequently have a sexual relationship with the perpetrator (e.g., risk of pregnancy). In this study, we investigated a parsimonious explanation that has previously been overlooked: Intercourse is more likely during nonconsensual sex when the victim and perpetrator have previously had a sexual relationship; thus, subsequent consensual intercourse may simply be a continuation of that prior relationship. A sample of 945 women completed an Internet-based survey, of whom 41% had experienced nonconsensual sex since age 14. As expected, victims who had intercourse with perpetrators prior to the nonconsensual sex event were significantly more likely than other victims to experience nonconsensual intercourse and to engage in subsequent consensual intercourse with the perpetrator. When considering only the small subsample of victims who never had a prior romantic or sexual relationship with the perpetrator, the odds of subsequent consensual intercourse were still significantly greater following nonconsensual sex with intercourse versus without intercourse.

Assessment of Introital Lubrication.

Vaginal vasocongestion and lubrication serve to prepare the vaginal lumen for sexual activity. Lubrication is important for sexual functioning and difficulties with lubrication are one of the most commonly reported symptoms of sexual dysfunction. Few studies have empirically examined how vasocongestion and lubrication relate to one another and there are currently no well-established measures of lubrication. In this study, we designed and tested a simple method to assess lubrication at the vaginal introitus in 19 healthy women, using litmus test strips. We examined the relationship between lubrication and vaginal vasocongestion (measured with a photoplethysmograph) when elicited by audiovisual sexual stimuli (male-female sexual interactions). Lubrication was elicited by the sexual stimuli and was strongly correlated with reports of sexual arousal. Unexpectedly, lubrication was not correlated with vasocongestion, even though the latter was also elicited by the sexual stimuli. We discuss the implications of these findings for informing our understanding of the female sexual response and the potential clinical and scientific utility of this new measure.