In 2001, the psychologists Roy F. Baumeister, Kathleen R. Catanese, and Kathleen D. Vohs carried out a meta-analysis of 150 different studies which asked: Is There a Gender Difference in Strength of Sex Drive? Intuitively, everyone already knew the answer to that question, but their mega-investigation categorically confirmed that, yes, men have more frequent and more intense sexual desires than women. Though it sounds like a simple solution to a rather obvious hypothesis, you can’t take out a ruler and measure libido in isolation. Interpersonal relationships are incredibly complex and within them, sexual desire is influenced by everything from upbringing, to wellbeing, to whether or not you have put the garbage out, or unstacked the dishwasher.
Because no single factor determines the motivation to have sex, Baumeister et al tackled the question from all angles. Literally. They established that: Men think about sex more often, experience more frequent sexual arousal, have more frequent and varied fantasies, desire sex more often, desire more partners, masturbate more, want sex sooner, are less able or willing to live without sexual gratification, initiate more and refuse less sex, expend more resources and make more sacrifices for sex, desire and enjoy a broader variety of sexual practices, have more favorable and permissive attitudes toward most sexual activities, have fewer complaints about low sex drive in themselves (but more about their partners), and rate their sex drives as stronger than women. Which is pretty damn conclusive.
Studies which show that men are more sexually driven than women are interesting, but the biological evidence for why those differences exist is more so. Testosterone has long been identified as integral to sex drive, and the fact that females have substantially less testosterone in their bodies is one obvious explanation for lower libido in women, however, oestrogen, a hormone we have in abundance, has also been implicated in decreased sexual desire. We all know that changes in oestrogen levels through the menstrual cycle creates peaks and troughs in sexual desire (e.g., Adams, Gold, & Burt, 1978). Less well known is the fact that surgically induced postmenopausal women who receive oestrogen therapy report depressed sexual desire, activity, and pleasure (Nathorst-Boos & von Schoultz, 1992; Sherwin et al., 1985; Shifren, Nahum, & Mazer, 1998) and decreased well-being (Nathorst-Boos, von Schoultz, & Carlstrom, 1993). In contrast, a double-blind, placebo-controlled, 52-week trial in which 814 women with hypoactive sexual desire disorder were randomly assigned to receive either a placebo, or a testosterone patch, supplementary testosterone was associated with significant increases in desire and decreases in distress, compared to the placebo (Davis et al 2008).
Further evidence to support the importance of testosterone comes from a study of 35 female-to-male transsexuals and 15 male-to-female transsexuals ( Van Goozen, Cohen-Kettenis, Gooren, Frijda, & Van de Poll 1995). A decrease in sexual interest and arousability was found among the male-to-female transsexuals who were administered anti-androgens and oestrogens. However female-to-male transsexuals, who were administered testosterone, reported heightened sexual interest and were more easily aroused.
Evolutionary theorists have argued that low libido in women is a protective mechanism which makes females less willing to engage in casual sex and therefore, less likely to get pregnant by partners who won’t invest in them and their offspring. If this were true though, lesbian couples might be expected to manifest higher levels of sexual activity than heterosexual couples (since the fear of pregnancy would be eliminated), however lesbian couples appear to have even less sex than heterosexual couples. A study by Blumstein and Schwartz (1983) found that in the first 2 years of a relationship, two thirds of the gay men, but only one third of the lesbians were having sex three or more times per week. After 10 years together, nearly half the lesbians, but only a third of the gay men, were having sex less than once a month, however the gay men who had largely ceased having sex after 10 years together were often having sex with other partners, whereas the lesbians who had ceased having sex together were not having sex with anyone. Data on masturbation (Oliver & Hyde, 1993) adds additional weight to the argument that lower libido in women is not explained by evolutionary theory since the vast majority of men (84%) masturbate, but only about half of women so (Jones & Barlow, 1990). Similarly, when asked if they masturbated at least once a year, 80% of boys but only 25% of girls reported at least yearly masturbation (Sigusch & Schmidt, 1973).
The evidence that male and female libidos differ is persuasive and there is certainly no doubt that the gulf between male desire and female disinterest causes a great deal of conflict in long- term relationships. Research by Byers and Lewis (1988) has found that almost half of all heterosexual couples disagree about sex, and every single disagreement involved the man desiring some sexual activity that his female partner did not. Likewise, men and women agree that female reluctance about sex is much more likely to occur than male sexual reluctance (O’Sullivan & Byers, 1995). Although the partner with low desire generally determines whether sex does, or does not happen, the overwhelming opinion in cases of mismatched desire is that the person with the lower libido is the one who needs to change. When sexual reticence becomes an insurmountable problem, women with hypoactive sexual desire are referred to sexual dysfunction clinics (for therapy and testosterone), or psychologists (for understanding and empathy), however the desire to have sex within a long-term relationship is so complicated that it doesn’t necessarily respond to this kind of well-intentioned tinkering.
Instead of trying to encourage these women to be more like men, is it worth stepping away from the presumption that the difference between male and female libido is a problem and questioning whether the push and pull between male and female libido might be an integral part of our sexual motivation? Although mismatched sex drives do cause conflict, a great deal of the associated unhappiness is driven by the expectation that women should be as sexually receptive as men want them to be. In reality, if we lived in a world where men and women possessed equal appetites for sex, where would the sexual tension be? Human sexuality seems to be based on the principle of opposing polarities and the male and female coupling appear to be a biological illustration of positive and negative electromagnetic interaction. Our differing sexual drives are matched in turn by our differently functioning, but complementary reproductive systems. If we accept that our biology is not accident, but design, then it makes sense to accept our distinctive libidos as a part of that.
Although men might argue to the contrary, if men and women had exactly the same drives, sex would almost certainly lose some of its appeal. Dopamine, the neurotransmitter which motivates us to seek sex is stimulated by unpredictability (Berridge and Robinson 1998) and Fmri scans have demonstrated that the anticipation of a reward generates more neural activity than the actual reward itself. As such, as soon as something, anything, that we enjoy becomes both accessible and predictable, we are inclined to lose interest in it. The gap between male and female libidos means that sex is never inevitable and this creates a variable schedule of reinforcement where reward cannot be presumed. In terms of training, variation is the most likely schedule to lead to permanence of behavior because the rewards are not predetermined and this sustains the trainee’s motivation. Basically, although men do want more sex than women, if women were always up for it, men would be less interested, so gender differences in sex drive are really rather clever. As Joyce Carol Oates once said, “Nothing is accidental in the universe”
Thanks to Robert T. Gonzalez for alerting me to the meta analysis. Is There a Gender Difference in Strength of Sex Drive? Theoretical Views, Conceptual Distinctions, and a Review of Relevant Evidence. Roy F. Baumeister, Kathleen R. Catanese, and Kathleen D. Vohs Personality and Social Psychology Review . 2001, Vol. 5, No. 3, 242–273