The male orgasm: pelvic contractions measured by anal probe.

Pelvic muscle contractions during sexual response can be monitored conveniently by the anal probe method described. Eleven young adult male subjects were each recorded for three sessions of masturbation to orgasm. Electrical signals from an anal pressure probe were automatically digitized by computer. Orgasmic contractions were easily distinguished from voluntary contractions by the steadily increasing intervals and complete muscle relaxation between orgasmic contractions. At orgasm each subject produced a characteristic series of contractions starting abruptly at an intercontraction interval of about 0.6 seconds, and continued for 10 to 15 contractions at an increasing increment of about 0.1 second per contraction. Pressure amplitude, representing the force of contractions, increased from the beginning of the regular series to a maximum at the seventh or eighth contraction. Area under the pressure curve, reflecting muscular exertion during contraction, generally increased throughout the regular series. Each man's pattern of contractions was very similar from one session to the next and distinguished his records from others'. Individuals' patterns could be grouped into three types, based chiefly on the location of the regular contraction series within the subjective span of orgasm. The most common type was a simple series of regular contractions. It had the shortest duration and fewest contractions. The next most common pattern began with the regular series, followed by a number of irregular contractions. This type was longest in duration. One man with a third type of intermediate duration, had a number of preliminary contractions before the series of regular contractions began in midorgasm.

Labial and vaginal blood volume responses to visual and tactile stimuli.

Five women volunteers participated in two experimental sessions designed to evaluate the response patterns of two objective psychophysiological measure of women's sexual arousal to different methods (and intensities) of sexual stimulation (i.e., an erotic film and manual self-stimulation). A vaginal photoplethysmograph was used to measure vaginal blood volume response and a labial thermistor-clip was used to measure temperature changes of one of the minor labia. Both measures usually covaried in a highly significant manner during both types of stimulation, with the largest responses typically being evoked by the physical stimulation. The response patterns for the two measures were also similar following both methods of stimulation if the woman did not experience orgasm; both measures decreased to some extent after the stimulation ended but usually remained well above the prestimulatory baseline. Orgasm, however, affected the two genital measures differently. The vaginal blood volume measure decreased dramatically during the reported orgasm, possibly because of vaginal contractions, and then increased to at least the preorgasmic level that occurred during the stimulation. The labial measure did not change during the reported orgasm but decreased relatively rapidly soon after.

A study of fantasy-based sexual arousal in women.

The self-reported use of sexual fantasy as an aspect of sexual behavior in natural settings was examined with respect to genital responding to both sexual fantasy and an erotic audiotape within the laboratory. It was predicted that subjects who self-reported a higher frequency of using sexual fantasy during either masturbation or sexual interaction with a partner in extralaboratory settings would be more highly responsive on genital measures of sexual arousal obtained when the subject was generating sexual fantasy within the laboratory. Forty-five female subjects (median age, 21) completed a battery of questionnaires, which included three scales of general imagery ability and frequency, and a detailed sexual history. All subjects then experienced an initial nonstimulated baseline period followed by a second baseline period and an exposure to an erotic audiotape. Genital responding was measured by vaginal photoplethysmography. Those subjects who reported more frequent use of fantasy during masturbation outside the laboratory showed greater genital responses during both fantasy and tape-elicited arousal than those reporting less use of masturbatory fantasy. One of the imagery questionnaires yielded a significant correlation with genital response in the fantasy condition. It appears that cognitive factors have predictive significance for measures of vaginal pressure pulse responses to erotic tape recordings and fantasies.

Sexual behaviour during ovarian cycles, pregnancy and lactation in group-living stumptail macaques (Macaca arctoides).

Sexual interactions were studied in a large, well-integrated group of stumptail macaques, continuously living together. Copulations with the highest-ranking male and with young males were equally distributed over the ovarian cycle. Copulations with other adults males also occurred during all cycle phases, but were most frequent peri-ovulatory. This was most distinct in conceptive cycles. Copulatory activity continued during early pregnancy, but was virtually absent during the middle and latter part of pregnancy and during lactation. Fluctuations in copulation frequency could be attributed to fluctuations in female attractivity (as measured by directed male masturbations), but not in proceptivity (spontaneous presents) or receptivity (acceptance ratios). However, hormonal influences on attractivity could be overruled by social factors. With regard to the expression of heterosexual behaviour, stumptail macaques seem to be less hormone-dependent than other primate species studied, both in the laboratory and under more natural circumstances.