"Pioneering sex researcher Alfred Kinsey, and later, Masters & Johnson, noted differences in sexual outcomes among heterosexuals, gay men and lesbian women as early as the 1940s and 1950s."
On average, men experience orgasm 85.1 percent of the time, with their sexual orientation making little difference.
For women, however, orgasm occurrence is less predictable.
On average, women experience orgasm 62.9 percent of the time during sex with a familiar partner - and this pattern varies with women's sexual orientation, with lesbian women experiencing orgasm more often than heterosexual or bisexual women.
The Indiana University study, titled "Variation in Orgasm Occurrence by Sexual Orientation in a Sample of U.S. Singles" and published online this week in the Journal of Sexual Medicine, uses a large-scale nationally representative sample to examine how self-identified sexual orientation can affect how often lovers have orgasms.
"These findings may contribute to promotion of more informed sexual health, by reminding us to pay attention to individual variation in research and clinical practice -- variation in sexual experiences, variation in sexual identities and variation in sexual outcomes," said lead author Justin R. Garcia, assistant professor of gender studies and research scientist at The Kinsey Institute. An evolutionary biologist, Garcia is also co-author of "Evolution and Human Sexual Behavior."The new study analyzed data from the 2011 wave of the Singles in America study, a now annual survey on the attitudes and behaviors of U.S. singles using nationally representative samples of single men and women ages 21 and older. The Singles in America sample was augmented to provide a better representation of gay men and lesbian women participants. In the current study, respondents were limited to men and women who had sex with a familiar partner during the previous year. It ultimately involved a final sample of 2,850 individuals.
"Moreover, to the extent that lack of orgasm is seen as a common and unwanted problem, learning more about orgasm in same-sex relationships may inform treatment for men and women in both same-sex and mixed-sex relationships," the authors wrote in the article.
What do scientists and clinicians know about orgasms?
Pioneering sex researcher Alfred Kinsey, and later, Masters & Johnson, noted differences in sexual outcomes among heterosexuals, gay men and lesbian women as early as the 1940s and 1950s. Yet little comparative research has been conducted since, leaving gaps in our understanding of sexual outcomes among sexual minorities. Understanding orgasm has implications for research and clinical and therapeutic knowledge involving sexual health and well-being.
Scientists do now know a lot about the psychological and physiological responses involved in orgasm, such as changes that occur in heart rates and blood pressure, and about neural and hormonal changes associated with arousal and climax. What for some can be intense sensations of pleasure are subjective, however, and big gaps remain in what researchers know about orgasm outside the lab. This includes what the researchers describe as "fundamental questions of how demographic factors may contribute to variations in individuals' orgasm experience."
There is even disagreement about the purpose of orgasms, with some evolutionary scientists arguing that orgasm is an adaptation to promote reproduction, while other evolutionary theorists such as IU's Elisabeth Lloyd, a co-author of the current study, argue there is insufficient evidence that such a link exists. Lloyd is author of "The Case of the Female Orgasm: Bias in the Science of Evolution."
Garcia said the range and variation among women in the current study raises numerous questions regarding the medicalization of orgasm, with women more often than men being diagnosed with orgasmic "disorders."
Why the range in experiences?
The researchers speculate on the patterns observed, suggesting it could be the result of such known factors as length of a sexual encounter (earlier research points to lesbian women spending more time per sexual session); differences in gendered and sexual attitudes across sexual orientation; and even possible biological factors, such as prenatal exposure to the hormones testosterone and estrogen.
The study authors note that the National Survey of Sexual Health and Behavior, also led by IU researchers, found a correlation between the rate of orgasms for men and women and the variety of sexual behaviors they reported.
Garcia said that partner communication - both spoken and unspoken - can play a big role in shaping sexual experiences and outcomes, including satisfaction.
"Some individuals will say what they want in a sexual encounter, or may be willing to say as much if their partner asked," Garcia said. "For others, communication may be nonverbal, with body language being key. This may also involve getting to know each other, both in and out of the bedroom, to understand what allows a particular sexual partner to experience a positive sexual outcome."
Importantly, however, Garcia also notes that orgasm should not be equated with sexual satisfaction, as the two can be quite independent, and that in some instances orgasm is not the goal of a sexual encounter.
The researchers said follow-up studies will look at other demographic factors that could influence rates of orgasm and other sexual outcomes among both men and women.
Co-authors are Elisabeth Lloyd from the Department of History and Philosophy of Science in the College of Arts and Sciences at Indiana University Bloomington; Kim Wallen from the Department of Psychology and Yerkes National Primate Research Center at Emory University; and Helen E. Fisher from the Department of Anthropology at Rutgers University. All are affiliated faculty with The Kinsey Institute.
The original rainbow flag, called the Freedom Flag, was devised by Gilbert Baker in 1978. The design has undergone several revisions since its debut with 8 colored stripes, and today the most common variant consists of 6 stripes: red, orange, yellow, green, blue, and violet.
Picture of Gilbert Baker's original Freedom Flag showing the meaning of the 8 colors.