There is currently no empirical basis for condemning most sexual practices, as strange or disgusting as people may find them. Nor is there any empirical basis for condemning sexual abstinence: in particular, there is at best weak support for the idea of a hunger-like sex drive. The one randomized controlled study of sexual frequency found that increasing couples' frequency of sex worsened their mood. Clinical trials of sexual behavior would be necessary to begin shedding light on the issue of what sexual habits are most beneficial.
The word "sex" often refers specifically to coitus (penile–vaginal intercourse), but various other activities are usually also considered sex, such as anal sex, fellatio, cunnilingus, and mutual masturbation. Sex is typically between two people, but then there's group sex. Typically the participants are of opposite sexes, but sometimes they aren't. Often the participants are roughly the same age and consider themselves to be in a passionate and intimate relationship although they aren't related by blood, but sometimes they're of vastly different ages or they don't even know each others' names or they're siblings. Usually sex is consensual, but sometimes it isn't: a party who doesn't really want to have sex has somehow been coerced into it. And if one of the participants is human, then usually they all are, but sometimes animals are included as well. Finally, masturbation is clearly a close relative of sex but is generally considered to be distinct from it for the simple reason that only one party is involved.
Are these practices ethical? Are they reasonable things to do? Some, to be sure, are not. Rape is unethical, almost by definition, and quite dangerous to victims, as discussed in a later chapter. People occasionally kill themselves masturbating: Blanchard and Hucker (1991) summarize 117 cases of autoerotic asphyxia in two Canadian provinces within fourteen years. And if media violence can make people more violent (it can, even if the likes of Jack Thompson have caricatured this view: see, for example, Anderson et al., 2010), then presumably violent sexual roleplaying can as well.
That said, I think these potentially problematic practices are the exceptions when it comes to sexual behavior. Most of the excuses people come up with for condemning certain kinds of sex don't hold water. Sex can cause unwanted pregnancies or transmit deadly diseases, but pregnancy is easy to avoid, and the risk of infection can be reduced to a low level. Sex can be disgusting (to only one person or to the vast majority of the human population), but simply because something is disgusting doesn't mean it's destructive or dangerous. Sex can violate religious codes, but religious codes by nature rest on belief in supernatural phenomena and are therefore indefensible from an empirical perspective. Sex can even violate prejudices that may well be innate to humans because of their value for evolutionary fitness, like the taboo against incest, but prejudice alone is no justification. For example, Haidt, Bjorklund, and Murphy (2000) told subjects a short story in which two siblings copulated consensually and with a condom. Less than 11 of the 30 subjects judged this to be acceptable, although 23 subjects together made 38 statements that they were dumbfounded, that is, statements "to the effect that they thought an action was wrong but they could not find the words to explain themselves".
This is not to say that blanket relativism is necessarily correct, either:
It has often been asserted (by some sexologists, sex educators, and sex therapists) that all sexual behaviours are approximately equal. This assertion springs from the confluence of political prejudices, weak research methods, and unquestioning devotion to the received lore. [Brody, 2006, p. 393]
Even if I wouldn't put it as strongly as Brody, I agree with his point that it is unjustifiable and dangerous to assume that every flavor of sex is equal. What we need, if we want to make prescriptive claims about sexual behavior—that is, claims about what people should do—is true experiments (clinical trials, of a sort) that randomly assign regimes of sexual behaviors and observe the consequences, for behavior as well as for health.1 Only experiments with random assignment can provide direct evidence of causation or the lack thereof. By and large, such research does not currently exist. In the meantime, we should suspend our scorn. It is inappropriate to condemn that to which we can't attribute potential harm. Hence the title of this chapter.
I know of one study in which sexual behavior, or at least the frequency thereof, was randomly assigned to subjects. Loewenstein, Krishnamurti, Kopsic, and McDonald (2015) observed 64 opposite-sex couples for three months, asking 35 of them to have sex twice as often as they usually did. Experimental couples indeed reported having sex more often than control couples: their mean frequency was greater by 0.4 occasions per week. But experimental couples had the lower mean score on a 14-point scale of mood, by 2.6 units. These results suggest that, despite observational findings that more sexually active people are happier (e.g., Blanchflower & Oswald, 2004), sex does not make people happy.
Our ignorance is a double-edged sword. The dearth of experiments on the consequences of sexual behavior vitiates criticism of sexual indulgence, but it also vitiates criticism of sexual abstinence. So, we can't recommend sex any more than we can condemn it, particularly in light of the findings of Loewenstein et al. (2015).
Perhaps because of the "political prejudices" of which Brody speaks, researchers have historically been less careful to suspend judgment when discussing abstinence than indulgence. For example, Kinsey, Pomeroy, and Martin (1948), who are famously nonchalant in their reporting of such controversial topics as "animal contacts" (bestiality), characterize another writer's claim that the "idea that sex intercourse is necessary for the health of the young man" is "mistaken" as a "moral evaluation" (p. 26), and they say of repeated attempts to stop masturbating "It is difficult to imagine anything better calculated to do permanent damage to the personality of an individual." (p. 514). In fact, the central argument of Jones's (1997) biography of Kinsey is that Kinsey pretended to be an impartial observer, but in reality sought to liberalize American sexual attitudes. Unfortunately, his extensive research on people's actual sexual behavior says nothing about how better or worse off people would be if they made different sexual choices, which I guess comes to show that the is–ought distinction is a perennial problem for scientists.
The sex drive need not exist
Political prejudice or not, though, anti-abstinence is a logical consequence of an idea with a long history among writers on sexuality and widespread acceptance among the public today: the sex drive. By "sex drive", I mean a motivation to seek sexual gratification that varies in a cyclic, time-dependent fashion like homeostatic motivations such as hunger, thirst, fatigue, and the desire to eliminate. The idea is that sex drive gradually builds up over time until it is reset by sexual activity. (The antithetical, less popular notion is that sexual desire eventually atrophies without gratification.) The word "libido" is often used interchangably with "sex drive", but "libido" is closely associated with Freud's peculiar ideas about sexual motivation providing the motivation for everything, so I avoid using it.
Freud (quoted in Apfelbaum, 1984) entertained a hydraulic notion of sex drive, in which "pressure on the walls of the seminal vesicles" had to be relieved by ejaculation. Kinsey et al. (1948) use the term "sexual outlet" to refer to orgasm frequency presumably because it is sex drive that one needs an outlet for. Closely tied to the idea of sex drive, albeit distinct, is the idea that low frequency of sexual activity is destructive to health or psychological functioning—if this idea were true, sex drive would be useful in the same fashion as hunger. Furthering the analogy with hunger, fear of sex has been called "sexual anorexia" (Carnes, 1998).
Recently, however, the notion of sex drive has been questioned. Bockting (2003) describes masturbation as "not a substitute for those who are sexually deprived, but an activity that stimulates and is stimulated by other sexual behavior". Toates (2009) makes similar claims and proposes that "[sexual] frustration does not reflect a pressure build-up arising from some diffuse regulatory substance[…] Rather[…] frustration would be triggered by (a) the thwarting of forward engagement with sexual incentives and (b) intrusive sexual imagery associated with lack of availability." The overall theme is a change of focus from state to stimulus. Toates's final point also suggests a causal role for people's mental imagery on sexual motivation, which is kind of the reverse of the idea that intrusive sexual imagery is a consequence of sex drive.
What empirical evidence can be brought to bear on the question of whether sex drive exists? Again, there are no relevant experiments. It is known that there exists a refractory period, a short time after orgasm during which sexual arousal is inhibited, at least among men (Levin, 2009). However, the few measurements of refractory periods that have been made, all in young men, have yielded intervals from orgasm to erection or from one orgasm to another on the order of 15 minutes (citing from Levin, 2009: Ekmekçioğlu, Inci, Demirci, & Tatlişen, 2005; Aversa et al., 2000; Mondaini et al., 2003). If the sex drive has more than a slight effect on sexual behavior, it must operate on the same timescale as intervals between instances of sexual activity in real life: hours, days, months, or years. Consider http://reddit.com/r/NoFap, an Internet community dedicated to abstinence from masturbation. Its users, who humorously call themselves "fapstronauts", characterize abstinence from masturbation as "the ultimate challenge"; their lapses should therefore be a clear example of the sex drive in action. But fapstronauts measure their time since last masturbatory orgasm in days, not minutes or hours, and consider 90 days a milestone. The refractory period is too short to play a role here.
One prediction of the notion of sex drive is negative relationships between various sources of orgasms. (By a "negative relationship", I mean that the more frequent one source of orgasm, the less frequent another.) In particular, laypeople sometimes suppose that nocturnal emission exists in order to keep the sex drive from growing too intense when one doesn't have enough orgasms while awake, and similarly that masturbation exists to compensate for insufficient sex. Data on the former point is scarce; in fact, data on anything about nocturnal emission is almost nonexistent. Kinsey et al. (1948) weakly suggest a negative relationship but don't examine the question quantitatively. Yu (2012) conducted a survey of 52 men that focused on pornography use and dream content. He found that nocturnal-emission frequency was negatively correlated with masturbation frequency; among several pairs of measures, the strongest relationship was a Spearman correlation of −.41.
There is more data on the relationship between masturbation frequency and sex frequency. The overall picture, while not consistent, is generally damaging to the idea of sex drive. Zamboni and Crawford (2002), using a large sample size of 543, found a small positive correlation (+.17) between masturbation frequency and sex frequency for both genders. Abramson (1973) found a positive correlation between masturbation frequency and sex frequency among women. Similarly, Davidson (1984) and Pinkerton, Bogart, Cecil, and Abramson (2002) found positive relationships between masturbation frequency and number of sex partners among women. Regnerus, Price, and Gordon (2017), using a large nationally representative sample of Americans, found a weak positive relationship among women and a weak negative relationship among men, both of which varied according to other variables such as whether the subject was married and the subject's reported sexual contentment. On the other hand, there are several failures to find significant correlations (Clifford, 1978; Greenberg, 1972; Kontula & Haavio-Mannila, 2002; and among men only, Abramson, 1973).
I know of a single relevant animal study. Thomsen and Soltis (2004) observed the masturbation patterns of wild male Japanese macaques. Masturbation rates were very high by human standards, with multiple instances per hour being typical. The presented data doesn't directly address the issue, but it suggests a negative relationship between masturbation and sex. On the subject of masturbation rates in general, and animals in particular, I reviewed literature with an eye to comparing typical masturbation rates between species (see appendix: http://arfer.net/w/esa/animast). The range goes from stallions, which seem to typically masturbate 10 times per day, to common chimpanzees, in which masturbation has only ever been observed in unusual rearing conditions. Among the species that have been studied, humans (or at least, American adults) have a fairly intermediate rate.
A recent sex survey with a sample size on the order of Kinsey et al.'s is the National Health and Social Life Survey (Laumann, Gagnon, Michael, & Michaels, 1994). I ran my own analysis of this dataset (for details, see appendix: http://arfer.net/w/esa/sexmastf) and found no correlation between sex frequency and masturbation frequency among women, and a small negative correlation (Kendall τ = −.1) among men.
What can we conclude? We have at most weak support for the notion of sex drive. I suggest we disbelieve in the sex drive until it's more convincingly demonstrated. In fact, a full-blown sex drive is not necessary to explain sexual self-control failures. We could instead attribute such failures to three phenomena that also play roles in drug addiction:
- A withdrawal phase in which desire does increase over time, but only for a relatively short time after the last indulgence. (Presumably, this effect can be attributed to gross changes in neurotransmitter concentrations in the brain.)
- Stimulus exposure (i.e., a reminder of sex or drugs).
- Spontaneous lapses in persistence without any changes in the relevant incentives. (For example, a result of the experiment of Luhmann, Ishida, & Hajcak, 2011, I learned of from personal communication is that, not infrequently, subjects would wait a few seconds for a delayed reward before spontaneously giving up and taking the smaller, immediately available reward.)
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Although Brody intends to demonstrate that coitus is superior to masturbation and other kinds of sex, at least for women, his research is insufficient for this goal, since it never randomly assigns subjects to coitus versus other-sex or masturbation conditions.