GENDER DIFFERENCES IN EROTIC PLASTICITY

 

Gender Differences in Erotic Plasticity: The Female Sex Drive as Socially Flexible and Responsive

 

2000 by the American Psychological Association

Volume 126(3), May 2000, p 347–374

Department of Psychology, CaseWestern ReserveUniversity

Roy F. Baumeister, Department of Psychology, CaseWestern ReserveUniversity, Cleveland, Ohio

 

 
 
 
 
 
 
 
 

 

 

Revised Date: July 6, 1999; Accepted Date: July 6, 1999

 

Responding to controversies about the balance between nature and culture in determining human sexuality, the author proposes that the female sex drive is more malleable than the male in response to sociocultural and situational factors. A large assortment of evidence supports 3 predictions based on the hypothesis of female erotic plasticity: (a) Individual women will exhibit more variation across time than men in sexual behavior, (b) female sexuality will exhibit larger effects than male in response to most specific sociocultural variables, and (c) sexual attitude–behavior consistency will be lower for women than men. Several possible explanations for female erotic plasticity are reviewed, including adaptation to superior male political and physical power, the centrality of female change (from no to yes) as a prerequisite for intercourse, and the idea that women have a milder sex drive than men.

 

 

Sex and mating seem to be accomplished in a fairly straightforward, predictable, even routine manner in many species of animals. Human sexuality, in contrast, has long been recognized as a rich, confusing tangle, in which biological drives, sociocultural meanings, formative individual experiences, and additional unknown factors play powerful roles. Among the most basic unresolved questions about human sexuality is that of the relative contributions of nature and culture: Does sexual response depend primarily on sociocultural factors such as meanings, context, relationship status, communication, norms, and rules—or is it mainly determined by hormones, genes, and other biological processes? Even in recent decades, theories about human sexual desire have differed radically in their relative emphasis on nature and culture. To be sure, hardly any theorist goes to the extreme of insisting that either nature or culture is totally responsible for determining the human sex drive, but the compromise formulations differ widely in their relative emphasis.

The two most influential theories about sexuality have been the social constructionist and the essentialist (DeLamater & Hyde, 1998). Social constructionist theories have regarded human sexual desire as shaped extensively by culture and socialization, often mediated by language as an ordering principle that is shared in common with other people. These theorists emphasize cross-cultural variation to argue for the cultural relativity of sexual desire (see, e.g., Staples, 1973). Who does what to whom sexually is regarded as a product of cultural rules and individual, linguistically mediated decisions rather than as a biological imperative. Social constructionist theories have also been invoked by feminists to depict human sexual desire as shaped by patriarchal society as part of its efforts to exploit and subjugate women (see, e.g., Kitzinger, 1987). Although social constructionists do not deny that there may be certain biological foundations to sexuality, they emphasize culture and social influence as the decisive factors in explaining human sexuality.

Essentialist theories, in contrast, propose that there are true and definite forms of sexuality that remain constant, even though situational factors may occasionally interfere with or shape their expression. As DeLamater and Hyde (1998) emphasized, evolutionary and sociobiological analyses of sexuality fall in this category, for they explain sexuality in terms of innate motivational patterns that have evolved to suit the reproductive contingencies of males and females so as to maximize the passing on of each person's genes (see, e.g., Buss & Schmitt, 1993). Some of these theories treat culture as a system adapted to accommodate the innate biological patterns(See, e.g., Symons, 1995)

 
 
 
 
 
 
 
 

. In any case, biology, not culture, is featured as the main source of causal explanations.

The present article offers yet another conceptualization of the relative contributions of nature and culture to human sexual desire. The point of departure is that there is no single correct answer that holds true for all human beings. Instead, I suggest that female sexuality, as compared with male, is more subject to the influence of cultural, social factors. Although male sexuality must frequently make concessions to opportunity and other external constraints, male desire is depicted here as relatively constant and unchanging, which suggests a powerful role for relatively rigid, innate determinants. Female sexuality, in contrast, is depicted as fairly malleable and mutable: It is responsive to culture, learning, and social circumstances. The plasticity of the female sex drive offers greater capacity to adapt to changing external circumstances as well as an opportunity for culture to exert a controlling influence. From the global perspective of the broader society, if controlling people's behavior is the goal, women's sexual patterns are more easily changed than men's.

Definitions

I use the term gender to refer to maleness and femaleness, whether biological or social, in order to reserve the term sex for activities leading to orgasm or genital arousal. The term erotic plasticity is used to refer to the degree to which a person's sex drive can be shaped and altered by cultural and social factors, from formal socialization to situational pressures. Thus, high erotic plasticity entails being subject to situational, social, or cultural influence regarding what types of partners and what types of sexual activities one would desire and enjoy. Desiring to perform the same act with a new partner does not necessarily constitute plasticity, for it is quite possible to have a stable, consistent desire to perform certain acts with many different partners.

The “sex drive” is a hypothetical construct, and research studies actually measure attitudes, behavior, and desire. The term attitude is used here to refer to general opinions and abstract rules that encompass broad categories and multiple situations. Desire refers to situation-specific feelings of sexual arousal and wanting to engage in particular acts with particular partners. Behavior refers to what the person actually does, such as physically engaging in particular sex acts. Desire may contradict attitudes, such as when a person feels an urge to have sex with a partner who is regarded as off-limits. Behavior can contradict either desire or attitude, such as when a person refrains from much-wanted sex or has intercourse with a forbidden partner.

Theory: Differential Plasticity

The central idea of this article is that the female sex drive is more malleable than the male, indicating higher average erotic plasticity. More precisely, female sexual responses and sexual behaviors are shaped by cultural, social, and situational factors to a greater extent than male. Plasticity could be manifested through changes in what is desired (e.g., type of partner, type of activity), in degree of desire (e.g., preferred frequency of sex, degree of variety), or in expression of desire (e.g., patterns of activity). Changes in attitudes may contribute to these behavioral changes.

Because debates about female sexuality are often perturbed by bitter conflicts based on implicit value judgments, it is important to address the value question explicitly. Frankly, I see almost no reason to think that it is better or worse to have high erotic plasticity, and so the present hypothesis does not entail that one gender is better (or better off) than the other in this regard. The difference may be important for predicting a variety of behavior patterns, attitudes, misunderstandings, and conflicts, but there is no inherent moral or practical superiority on either side.

There are two small exceptions to the value-free tone of my hypothesis. That is, two small value judgments could be made, and they point in opposite directions. The first is that it is generally better to be flexible because one can adapt more readily to changing circumstances. The capacity to change is inherently adaptive, and being adaptive is good. In this respect, women may be better off than men if the present hypothesis is correct because their sexuality can adjust more easily and readily. Thus, if changes in social circumstances place equal demands for adjustment on males and females, the females will be more successful than the males at making these adjustments, or they will be able to achieve that success with less difficulty.

The other exception is that higher erotic plasticity may render a person more vulnerable to external influences, with the resulting possibility that one could end up being influenced to do things that are not in one's best long-term interests. In simple terms, it may be easier to talk a woman into doing something sexual that she does not really want to do or something that is not good for her, as compared with talking a man into doing something that is comparably contrary to his wishes and needs. The present hypothesis has to do with receptivity to influence, and being receptive to influence can under some circumstances take on a negative tone (e.g., gullibility).

Neither of these value-linked effects is likely to be widespread or powerful. Hence, erotic plasticity should not be invoked to argue for the superiority of either gender.

Empirical Predictions

The hypothesis of differential erotic plasticity permits empirical predictions. A first, basic prediction is that intraindividual variation (i.e., within-person variance) in sexual behavior will be greater among women than men. If women are malleable in response to situational and social factors, then as a woman moves from one situation to another, her sexual desires and behaviors may be subject to change. The lesser (hypothesized) flexibility of men would mean that male sexual patterns will remain more stable and constant across time and across different situations. (Lack of opportunity may be an exception: A man's sexual behavior may depend on whether he can find a willing partner.) Physical changes, such as ill health or major hormonal changes, might well have a strong effect. But as regards changing social situations and different life circumstances, the average man's desires should remain more stable and constant than the average woman's.

This theory does not extend to making predictions about interindividual variations, because these could well depend on innately or genetically prepared patterns. The men in a given culture may collectively have more variations in their individual sexual appetites than do the women without violating the hypothesis of female plasticity. A familiar example of gender differences in interindividual variance in genetically influenced traits is found in research on mental retardation and intelligence: The two genders have nearly identical mean IQ scores, but the males have higher variance, therefore being proportionally overrepresented at both extremes (Jensen, 1998; Lehrke, 1997; J. A. F. Roberts, 1945). Such patterns are plausible with sexuality, too, and I am not making predictions about interindividual variance (although evidence about paraphilias are considered briefly among the possible limitations and counterexamples). The present hypothesis concerns only intraindividual variance: Once a man's sexual tastes emerge, they are less susceptible to change or adaptation than a woman's.

A second prediction is that specific sociocultural factors will have a greater impact on women's sexuality than on men's. To put this prediction in more precise, statistical terms, the sociocultural variables will have bigger effect sizes in predicting responses of women than of men. Thus, women will vary more than men from one culture to another and from one historical period to another. Socializing institutions, such as schools and churches, should produce bigger changes in women than in men with regard to sexual behavior.

A final prediction is that attitude–behavior consistency (with regard to sex) will be lower among women than men. If female sexual response is malleable by situational and social factors, then a woman's behavior cannot be easily predicted by her attitudes (especially general, abstract attitudes). In simple terms, her sexual responses depend more on external context than on internal factors, relative to those of males, and so her attitudes are less likely to determine her behavior. She may, for example, hold an attitude in favor of using condoms or against anal intercourse, but situational factors may intrude to cause her to act contrary to those attitudes under some circumstances (and even to desire such attitude-contrary acts). This prediction is methodologically a useful complement to the first one because it avoids the confound that data on women are somehow simply more conclusive or reliable than data on men. The erotic plasticity hypothesis predicts that cultural and social factors will show higher correlations with sexual responses of women than men—whereas attitude–behavior correlations will be lower for women than for men.

Reasons for Plasticity

Why should women have more erotic plasticity than men? I have three different hypotheses, each of which could offer some potential insight into the gender difference in erotic plasticity.

The first is based on the difference in power. On average, men are physically stronger and more aggressive than women, and they also tend to hold greater sociopolitical and economic power. If two partners' sexual wishes were to differ, the man would have several advantages over the woman for getting his way. Greater flexibility on the part of women would be one adaptive response to the standard problem of bonding with someone who would be able to impose his desires by means of physical coercion or social power, should that ever become necessary (as he saw it). Biologists and evolutionary psychologists believe that the relative superiority of male physical power is strongly linked to male reproductive patterns and goals (such as male competition under circumstances of extreme polygyny; Gould & Gould, 1997; Ridley, 1993), and feminists emphasize that male political power shapes the sexual interactions between the sexes and results in the cultural suppression of female sexuality. The present suggestion could be seen as another such process, in which women became socially malleable as an adaptation to male power.

The second is that flexibility may be an inherent requirement of the female role in sex. The simplest version of this would emphasize that most societies (including other species similar to humans) limit sexual activity by having the female refuse sexual offers and advances from most males. Of course, if females refused all male advances, the species would fail to reproduce. Women are negative toward most potential sex partners (i.e., most men) but occasionally switch to positive. A negative response is the woman's default option, as it were. In practice, this entails that sex generally commences when the woman switches her initially negative stance to a positive one. That is, when a couple begins having sex, it is mainly because the woman has changed her decision: The woman initially rejects the man's advances but later changes her vote from no to yes. The centrality of this change (from no to yes) in female sexuality requires each woman to have a certain degree of flexibility, and the broader patterns of erotic plasticity would follow from this foundation. Change requires changeability and hence begets further change.

The third possible explanation is based on differential drive strength. This would invoke the politically unpopular but theoretically plausible view that women have a weaker sex drive than men. A relatively weak motivation is presumably easier to redirect, channel, or transform than a powerful one. Women could thus more easily be persuaded to accept substitutes or alternate forms of satisfaction, as compared with men, if women's overall sexual desires are milder.

Proximal Sources of Plasticity

These root causes may be translated into the actual degree of behavioral plasticity of living individuals either through innate, genetic patterns or by social learning processes and personal experiences (even conscious adaptations). The nature of the mediating, proximal causes is not easily resolved, but a few speculative suggestions may be offered. How, then, is erotic plasticity actually instilled?

The possibility that it is biologically based must be considered. Many sexuality-based traits are supposedly genetically prepared by the X chromosome, of which women have two and men only one. Having two different sets of relevant genes could allow for greater flexibility than having only one. Specifically, the two X chromosomes could carry different prescriptions for behavior, and hence it would be up to the environment to determine which one would prevail. Males, in contrast, would receive a single and unambiguous genetic program, leaving less opportunity for the environmental influence.

Hormone levels provide another plausible basis for differential plasticity. Research has generally found that testosterone is the single hormone that has the greatest effects on sexual behavior in both males and females. Because males have substantially more testosterone than females, male behavior may be more subject to its causal influence than female behavior. (On the other hand, female receptors may be more sensitive to testosterone than are those of males, which could offset the difference in quantity of the hormone.)

In another relevant line of argument, T. Roberts and Pennebaker (1995; also Pennebaker & Roberts, 1992) have concluded that men are generally better than women at perceiving and detecting their inner bodily states. They noted that in socially impoverished environments such as laboratories and hospitals, males consistently outperform females at estimating their own bodily reactions such as blood pressure, heartbeat, stomach contractions, respiratory resistance, finger temperature, and blood glucose levels. This gender difference disappears when measures are taken in naturalistic and meaning-rich settings, in which multiple cues about sources of feelings are available. Roberts and Pennebaker proposed that men judge their emotional and arousal responses based on direct detection of physiological cues, whereas women rely more on social and situational cues to know how they respond. If this is true generally for all emotions, it would presumably be even stronger for sexual responses, because the signs of arousal are much more salient and unambiguous in the male than in the female. This argument could also explain why testosterone and other inner, biochemical realities have stronger effects on male than female sexuality: If men are more attuned to their inner bodily states, then their level of testosterone would exert a stronger effect on their behavior.

Yet another possibility is that males have evolved to be more strongly driven by natural and genetic factors. Some authors have speculated that there may be a higher rate of mutations among males than females. One such speculation is that the Y chromosome (unique to males) might be a popular target of mutations. Nature may have targeted males and the Y chromosome for trying out new mutations because the greater reproductive variance among males would give more opportunity for natural selection to operate (discussed by Kacelnik, 1999). The difference in reproductive variance is well established. In human beings, for example, most females produce at least one child, and hardly any woman has more than 10 babies. In contrast, many men have zero offspring, and others exceed 10 by substantial amounts (Gould & Gould, 1997; Ridley, 1993). Thus, men exceed women at both extremes of reproductive outcomes (i.e., more at zero and more over 10). These differences help determine how long natural selection takes to sort out whether a particular mutation increases or decreases reproductive success. The relatively small variation in female reproductive outcomes entails that many generations would be required for a given mutant to prove itself better or worse than the original. In contrast, a mutation in males might yield bigger effects within fewer generations: An adaptive mutation might help a male produce dozens of offspring, and a maladaptive one would quickly be eliminated from the gene pool. Because males thus make more efficient vehicles with which to select and evolve, therefore, male sexual behavior may have gradually become more encumbered with such biological influences.

Evolutionary arguments often invoke differential reproductive goals for men and women (see, e.g., Buss & Schmidt, 1993; Gould & Gould, 1997; Ridley, 1993). Because women cannot have as many offspring as men, they are presumably more selective about sex partners. Although one could argue a priori that the greater selectivity could lead to lower plasticity (because the woman can ill afford to compromise or take chances), one might also suggest that selectivity mandates a complex, careful decision process that attends to subtle cues and contextual factors and that this very complexity provides the basis for greater plasticity.

The biological and evolutionary arguments suggest searching for erotic plasticity in other species, which is beyond the expertise of the author and the scope of this review. Still, an important recent study by Kendrick, Hinton, Atkins, Haupt, and Skinner (1998) is relevant. In an experimental design, newborn sheep and goats were exchanged, so that the sheep were raised by goats and vice versa. After they reached adulthood, they were reunited with their biological species, and their mating preferences were observed. Consistent with the hypothesis of female erotic plasticity, the adult females were willing to mate with either species. The males, in contrast, preferred only their adoptive species and refused to mate with their biological conspecifics, even after living exclusively with their own kind for 3 years. These results suggest that male sexual inclinations are based on a process of sexual imprinting that occurs early in life and then remains inflexible, whereas female sexual inclinations can continue to change in adulthood.

The hypothesis that male sexuality is subject to an early imprinting process that is irreversible (as opposed to reversible influences on female sexuality) suggests that both genetic preparation and early experiences are relevant. It qualifies the broad hypothesis about greater female plasticity: Perhaps there is a stage early in life during which male sexuality is highly receptive to social, environmental influences. After this imprinting, however, male sexuality remains relatively rigid and inflexible, whereas female sexuality retains plasticity throughout adolescence and adulthood.

This dovetails well with a recent theory of sexual orientation put forward by Bem (1996, 1998). Bem rejected direct genetic influences on sexual orientation but suggested that genes may affect temperament, which may in turn lead a young person to prefer either males or females as friends and playmates. Later, the less familiar gender creates arousal and thereby becomes the focus of sexual attraction. Bem (1996, 1998) has specifically suggested that his theory predicts that female sexual orientation will be more fluid and changeable than male, because little girls are more likely than little boys to have opposite-sex friends and playmates. Because “women actually grow up in a phenomenologically less gender-polarized culture than do men” (Bem, 1998, p. 398), men tend to be polarized into finding only males or only females sexually appealing, whereas women's greater familiarity with both genders enables them to be attracted to either or both. One can extend Bem's argument to propose that this greater bisexual orientation of women will provide the foundation for other forms of plasticity and change. This extension is similar to the argument I made regarding change and the female sexual script, except that the cause of plasticity depends entirely on social factors and early experiences, and any contribution by genetic factors is indirect.

Other, more purely cultural arguments could be proposed to account for differential plasticity. These would suggest that culture teaches men to obey their biological promptings but teaches women to ignore theirs and obey social prescriptions instead. These arguments seem relatively implausible in light of evidence that, throughout history, the prevailing stereotypes have regarded women as closer to nature than men and that in fact when society does try to change women's behavior it usually does so by telling women what is allegedly in their biological nature, as opposed to teaching them to ignore their biological factuality (see, e.g., Margolis, 1984). Still, it is conceivable that new, more plausible versions of these explanations may be forthcoming.

Causal Processes

Last, it is helpful to consider the possible causal processes, even though these extend the theoretical argument beyond what can be tested against the currently available research literature. If the balance of natural versus cultural determinants of sexuality differs by gender, then the causal processes that direct sexual behavior are also likely to differ.

Natural processes are typically mediated by biochemical processes. Hormones such as testosterone are likely to exert strong and direct effects. Despite the fact that the exact processes leading from genes to behavior are not fully understood (although this field is one in which substantial advances are anticipated in the next decade), one assumes that biochemical factors play a crucial role in mediating such processes.

In contrast, cultural processes are mediated by meanings, which is to say informational, symbolic concepts that can be expressed in language and communicated between group members. Norms, attitudes, rules, expectations, and relationship concepts provide contexts from which specific sexual acts and decisions can draw meaning. Behavior depends on these meanings.

The hypothesized gender difference thus predicts that male sexuality will be shaped more than female sexuality by biochemical factors, including genetics and hormones. In contrast, female sexuality will be more meaning-driven than male sexuality, so that context and interpretation shape women's sexual decision-making (and other sexual responses) more than men's.

Hypothesis Formation: The Sexual Revolution

The present investigation was initially stimulated by a conclusion drawn by Ehrenreich, Hess, and Jacobs (1986) in their history of the sexual revolution in the United States, namely, that that revolution was mainly a change in women not men. Men's sexual desires and attitudes were pretty much the same after the sexual revolution as before it, although men had more opportunities for finding satisfaction afterward. It was women who changed fundamentally. Indeed, according to Rubin (1990), women changed several times, at first embracing a promiscuous enjoyment of casual sex like men, then shifting toward a more limited permissiveness that accepted sex in affectionate relationships but did not eagerly seek out sex with strangers (see also Robinson, Ziss, Ganza, Katz, & Robinson, 1991).

The conclusion that the sexual revolution was primarily a change in female sexual attitudes and behaviors, rather than male, was made by other researchers beyond Ehrenreich et al. (1986). Arafat and Yorburg (1973) and Birenbaum (1970) had already made similar observations. Empirical studies, particularly those that surveyed the same type of sample (e.g., the same college campus) at repeated intervals, consistently found that women's attitudes and behaviors changed more than men's during the 1960s and early 1970s (Bauman & Wilson; 1974; Croake & James, 1973; DeLamater & MacCorquodale, 1979; Schmidt & Sigusch, 1972; Sherwin & Corbett, 1985; Staples, 1973), continuing even into the 1980s (Robinson et al., 1991). Well-constructed national surveys corroborated these conclusions by comparing older people, who had come of age before the sexual revolution, with younger people, whose sexual prime had occurred after the revolution, and these too found bigger differences in women than men (Laumann, Gagnon, Michael, & Michaels, 1994; Wilson, 1975).

As one good example, Laumann et al. (1994) provided data on the proportion of respondents who had had five or more sex partners by the age of 30 (an age when most people have married and ceased accumulating new sex partners). For the oldest cohort, who came of age prior to the sexual revolution, 38% of men had had five or more sex partners by age 30, whereas for the younger cohort, the proportion increased slightly, to 49%. For women, the corresponding numbers are 2.6% and 22.4%. The sexual revolution thus increased men's likelihood of having many partners by 11 percentage points, or by about a fourth, whereas it multiplied women's likelihood by a factor of more than eight and by 20 points. Put another way, the sexual revolution produced a modest increase in the number of men having five or more sex partners, reflecting perhaps nothing more than increased opportunity, but it radically transformed many women's lives and created a large category of multipartnered women that had been almost nonexistent prior to that revolution (Laumann et al., 1994).

The implication that women were changed more than men by the sexual revolution suggested the broader possibility that female sexuality is more historically malleable than male. The present investigation was spurred by this hypothesis. Given the difficulty of drawing firm conclusions about psychological principles from single historical events, especially highly complex ones influenced by multiple factors, I found it necessary to look elsewhere for evidence.

Evidence of Female Plasticity

The method of reviewing the literature was as follows. I began with the most recently available volume of the Journal of Sex Research (1996 at the time) and worked backward to the first volume, reading all abstracts and all relevant articles. By covering the major journal in its entirety, I hoped to minimize the dangers of selective review and confirmation bias. The Archives of Sexual Behavior then received a similar treatment by a research assistant. These articles offered a useful starting point, and their reference lists were used to find further sources in other publications. The National Health and Social Life Survey (NHSLS; Laumann et al., 1994) was carefully scrutinized, inasmuch as it offers the most comprehensive and scientifically valid survey data (and indeed it is covered in a separate section). Additional sources were suggested by colleagues and by helpful reviewers of a previous draft, and more recently published work was added during revisions.

Data on sexuality are often less than perfect, partly because of the ethical and practical difficulties of studying sex. A summarizing discussion of limitations in the data and general critique is provided after the evidence itself is presented. Alternative explanations are discussed at that point, but two of them deserve to be acknowledged at the outset.

First, it is conceivable that there are more efforts to control female than male sexuality. This is not actually an alternative explanation in the usual sense, because it is fully compatible with the view of greater female plasticity. If female sexual behavior can be regulated more effectively than male sexuality, then it would make sense for society to focus its efforts on controlling females. Still, it is plausible that some findings regarding greater variation or causal impact among females could reflect variation in sociocultural controls rather than differential plasticity. The so-called double standard may be one example, if indeed it means that society permits or has permitted men to do things forbidden to women.

Second, the findings regarding the power of specific sociocultural variables to change sexual behavior have to contend with different baselines in some cases. For example, if education increases the proportion of men who engage in some sexual practice from 70% to 80% while increasing the corresponding proportion of women from 30% to 80%, some readers might refuse to regard this as evidence of greater impact on women: It might be that the effect of education on men was limited by a ceiling effect.

Intraindividual Variability

The first major prediction is concerned with intraindividual variability. If erotic plasticity is greater among females, then women should show more variation across their individual sexual histories than men. The focus is on whether particular persons exhibit changes in their sexuality across time.

One gender difference in intraindividual variability was noted by Kinsey, Pomeroy, Martin, and Gebhard (1953). Although their sampling has been criticized as not up to the best modern standards, that criticism is irrelevant to this finding, and their data on individual sexual histories are among the most detailed ever collected. They found that some women, but hardly any men, showed patterns of substantial swings in degree of sexual activity. A woman might go through a phase of having a great deal of sex, then have no sexual activity of any sort for months, and then enter into another phase of having a great deal of sex. If a male were to experience a romantic break-up or a physical separation from his sex partner, he would tend to keep his orgasm rate constant by resorting to masturbation or other activities, but women did not necessarily do this. “Discontinuities in total outlet are practically unknown in the histories of males,” unlike females (Kinsey et al., 1953, pp. 681–682). These discontinuities are thus an important confirmation of the hypothesis of female erotic plasticity.

Intraindividual change was the focus of an investigation by Adams and Turner (1985), who compared the reports of current sexual activity among an elderly sample (age 60–85) with the same people's retrospective reports of what they did in young adulthood (age 20–30). Adams and Turner pointed out that most studies of the effects of aging on sexuality simply emphasize reductions in drive and energy and hence decreased sexual activity, and so they looked especially for any signs of increasing activity. Only a small minority of their sample showed increases on any of the measures, but this minority was predominantly female. Thus, one pattern of intraindividual change over several decades (increasing sexual activity) was found mainly among females, and this pattern is of particular interest because it is not confounded by loss of vigor or declining health, which would make evidence of reduced sexual activity less relevant to the present theory.

Some of Adams and Turner's (1985) most interesting data concern masturbation. They found that in comparisons of young adulthood with old age, women showed remarkable, significant increases in masturbation (10% to 26%), whereas men showed a nonsignificant decrease over the same age span (32% to 26%). Adams and Turner noted that their sample overrepresented married women, so the change does not simply reflect a shift into masturbation as the women lost their partners. Even more important, Adams and Turner reported that the old men who masturbated were typically continuing a pattern of masturbation that was present in young adulthood, whereas the women who masturbated in their 20s had typically discontinued that activity late in life. (Also, given the increase in overall numbers, the strong majority of the women who masturbated in old age had not done so in their 20s.) The authors concluded that the masturbation data showed that “women displayed more plasticity in behavior than men” (p. 134).

Undoubtedly, some degree of flexibility would be useful in adapting to marriage because the requirement of coordinating one's sexual activities with a particular partner over a long period of time presumably requires some compromises unless the couple is perfectly matched and their desires wax and wane in complete synchrony, which seems unlikely. Data on sexual changes in the adaptation to long-term marriages were provided by Ard (1977), who, in a 20-year follow-up of a longitudinal study, asked the individuals who had remained married for over two decades how much they had changed from their early ideas, habits, and expectations regarding sex. Wives were somewhat more likely than husbands (13% to 9%) to claim that they had changed “a great deal,” although this difference fell short of significance. Because some people might inflate their self-reported change in order to look good, Ard also asked people how much their partners had changed along the same lines, and these partner reports confirmed—significantly, this time—that the women had changed more than the men: 12% of the husbands, but only 6% of the wives, reported that their spouse had changed a great deal.

The greater change by women than men in adapting to marriage is especially remarkable given some other features of Ard's (1977) data. When asked about their current frequency of sexual activity and their current preferences for frequency of sexual activity, the wives' answers indicated that their marital practices corresponded almost precisely to the amount of sex they wanted, whereas the men reported a significant gap between what they wanted and what they were able to have. Thus, men were not getting what they wanted on this important measure, whereas women were—yet still the evidence showed that women had adapted more than men. Possibly, women succeeded better than the men at adjusting their expectations into line with what they were getting, which could be another manifestation of plasticity and would presumably be a very beneficial adaptation.

Marriage is certainly not the only type of relationship that can produce change in sexual attitudes. Harrison, Bennett, Globetti, and Alsikafi (1974) found that women changed their sexual standards toward being more permissive as they accumulated dating experience. Men did not seem to change as a function of dating experience. One might have predicted that the necessity of compromise would produce change in attitudes in both genders, but Harrison et al. found change only in the females. Reiss (1967) likewise found that women increased their sexual permissiveness after having steady dates or love relationships, whereas the effects of such experiences on men were small and nonlinear. Reiss reported that 87% of the females, as opposed to 58% of the males, had come to accept sexual behavior that initially made them feel guilty. Of these, far more more females than males cited the relationship with the opposite-sex partner as the key factor in bringing about this change. Thus, again, the data suggest greater sexual adaptation in relationship contexts by women.

In the 1960s and 1970s, consensual extramarital sex increased, and researchers were able to examine how people adapted to this unusual behavior (often called swinging). J. R. Smith and Smith (1970) studied this phenomenon and concluded that “women are better able to make the necessary adjustments to sexual freedom after the initial phases of involvement than are men” (p. 136). They noted that this greater adaptability of women was especially remarkable in light of the fact that it had generally been the men who initiated the involvement in swinging. Although Smith and Smith failed to provide quantitative evidence to back their claim of the superior adaptation of women, their observation is noteworthy because it confirms one of the presumptive advantages of plasticity, namely, greater capacity to adapt to new circumstances.

Some of the best and most useful data on intraindividual variability concern sexual orientation and same-sex activity. Operationally, this can be studied by investigating whether homosexual individuals have had heterosexual experience, which would suggest a higher degree of plasticity in their sexual orientation. Beginning with Kinsey's research (Kinsey, Pomeroy, & Martin, 1948; Kinsey et al., 1953), many studies have found that lesbians are more likely to have had heterosexual intercourse than gay males. This effect is especially remarkable given the greater promiscuity of males, although it might have something to do with the greater sexual initiative exhibited by males (which would mean that heterosexuals would likely approach lesbians more than gay males). Savin-Williams (1990) found that four fifths of gay women, but only about half (54%) the gay men, had had heterosexual intercourse. In a quite different sample consisting of gay youth in New York City, Rosario et al. (1996)

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