In evolutionary psychology and behavioral ecology, mating strategies refer to the set of behaviors used by individuals to attract, select, and retain mates. Mating strategies overlap with reproductive strategies, which encompass a broader set of behaviors involving the timing of reproduction and the trade-off between quantity and quality of offspring (see life history theory). Relative to other animals, human mating strategies are unique in their relationship with cultural variables such as the institution of marriage. Nevertheless, commonalities can be found between humans and nonhuman animals in mating behavior (see animal sexual behavior).
Research on human mating strategies is guided by the theory of sexual selection, and in particular, Robert Trivers' concept of Parental Investment. Trivers defines parental investment as âany investment by the parent in an individual offspring that increases the offspring's chance of surviving (and hence reproductive success) at the cost of the parent's ability to invest in other offspring.â Trivers posited that differential parental investment between males and females drives the process of sexual selection, which leads to the evolution of sexual dimorphism in mate choice, competitive ability, and courtship displays (see also secondary sex characteristics). In humans, females make a larger parental investment than males (i.e. nine months of gestation followed by childbirth and lactation). While human males invest heavily in their offspring as well, their minimum parental investment is still lower than that of females. Hence, evolutionary psychologists have predicted a number of sex differences in human mating strategies.
Sex differences in mating strategies
Because of their lower minimum parental investment, men can achieve greater reproductive success by mating with multiple women than women can achieve by mating with multiple men. Evolutionary psychologists therefore argue that ancestral men who possessed a desire for multiple short-term sex partners, to the extent that they were capable of attracting them, would have left more descendants than men without such a desire. Ancestral women, by contrast, would have maximized reproductive success not by mating with as many men as possible, but by selectively mating with those men who were most able and willing to invest resources in their offspring. One classic study found that when college students were approached on campus by opposite-sex confederates and asked if they wanted to âgo to bedâ with him/her, 75% of the men said yes while 0% percent of the women said yes. Evidence also indicates that, across cultures, men report a greater openness to casual sex, a larger desired number of sexual partners, and a greater desire to have sex sooner in a relationship. These sex differences have been shown to be reliable across various studies and methodologies. However, there is some controversy as to the scope and interpretation of these sex differences.
Evolutionary psychologists have predicted that men will generally place a greater value on youth and physical attractiveness in a mate than will women. Youth is associated with reproductive value in women, and features that men find physically attractive in women are thought to signal health and fertility. Men who preferentially mated with healthy, fertile, and reproductively valuable women would have left more descendants than men who did not. Since menâs reproductive value does not decline as steeply with age as does womenâs, women are not expected to exhibit as strong of a preference for youth in a mate. Evolutionary psychologists have also predicted that women will be relatively more attracted to ambition and social status in a mate because these characteristics are associated with menâs access to resources. Women who preferentially mated with men capable of investing resources in their offspring, thereby ensuring their offsprings' survival, would have left more descendants than women who did not. Evolutionary psychologists have tested these predictions across cultures, confirming that men tend to report a greater preference for youth and physical attractiveness in a mate than do women, and that women tend to report a greater preference for ambition and social status in a mate than do men. Some sex differences in mate preferences may be attenuated by national levels of gender equity and gender empowerment. The specific role that culture plays in modulating sex differences in mate preferences is subject to debate.
Individual differences in mating strategies
Sociosexual Orientation Inventory
Average differences in mating strategies between the sexes do not entail uniformity in mating strategies within the sexes, and in humans, such within-sex variation is substantial. Individual differences in mating strategies are commonly measured using the Sociosexual Orientation Inventory (SOI), a questionnaire that includes items assessing past sexual behavior, anticipated future sexual behavior, and openness to casual sex. Higher scores on the SOI indicate a sexually unrestricted mating strategy, and lower scores on the SOI indicate a sexually restricted mating strategy. Several studies have found that scores on the SOI are related to mate preferences, with more sexually restricted individuals preferring personal/parenting qualities in a mate (e.g. responsibility and loyalty), and with less sexual restricted individual preferring qualities related to physical attractiveness and social visibility. Other studies have shown that SOI scores are related to personality traits (i.e. extraversion, erotophilia, and low agreeableness), conspicuous consumption in men as a means to attract women, and increased allocation of visual attention to attractive opposite-sex faces.
Short-term vs. long-term mating
Evolutionary psychologists have proposed that individuals may adopt conditional mating strategies in which they adjust their mating tactics to relevant environmental or internal conditions. To the extent that ancestral men were capable of pursuing short-term mating strategies with multiple women, the evolutionary benefits are relatively straightforward. Less clear, however, are the evolutionary benefits that women might have received from pursuing short-term mating strategies. One prominent hypothesis is that ancestral women selectively engaged in short-term mating with men capable of transmitting genetic benefits to their offspring such as health, disease resistance, or attractiveness (see good genes theory and sexy son hypothesis). Since women cannot inspect men's genes directly, they may have evolved to infer genetic quality from certain observable characteristics (see indicator traits). One prominent candidate for a "good genes" indicator includes fluctuating asymmetry, or the degree to which men deviate from perfect bodily symmetry. Other candidates include masculine facial features, behavioral dominance, and low vocal pitch. Evolutionary psychologists have therefore predicted that women pursuing a short-term mating strategy will have higher preferences for these good genes indicators, and men who possess good genes indicators will be more successful in pursuing short-term mating strategies than men who do not. Indeed, research indicates that self-perceived physical attractiveness, fluctuating asymmetry, and low vocal pitch are positively related to short-term mating success in men but not in women. Women prefer purported good genes indicators more for a short-term mate than for a long-term mate, and a related line of research shows that womenâs preferences for good genes indicators in short-term mates tends to increase during peak fertility in the menstrual cycle just prior to ovulation.
Environmental predictors of mating strategies
In 2005, the evolutionary psychologist David Schmitt conducted a multinational survey of sexual attitudes and behaviors involving 48 countries called the International Sexual Description Project (ISSR). Schmitt assessed relationships between several societal-level variables and average scores on the SOI. One variable that was shown to significantly predict a nationâs average SOI score was the Operational Sex Ratio (OSR), which was defined by Schmitt as âthe relative balance of marriage-age men versus marriage-age women in the local mating pool.â When one sex is scarce relative to the other sex, the less-scarce sex may compete more intensely for access to the scarcer sex. One way in which the more numerous sex might compete is by displaying the attributes that are most desired by the scarcer sex. Since men have a greater desire for casual sex (see above), societies with more women relative to men were predicted to exhibit higher scores on the SOI than societies with more balanced or male-biased sex ratios. This prediction was confirmed: OSR was significantly positively correlated with national SOI scores. Another variable that Schmitt predicted would influence SOI scores was the need for biparental care. In societies where extensive care from both parents is needed to ensure offspring survival, the costs of having sex with an uncommitted partner are much higher. Schmitt found significant negative correlations between several indices of need for biparental care (e.g. infant mortality, child malnutrition, and low birth-weight infants) and national SOI scores.
Another important societal variable for mating strategies is the threat of infectious disease or pathogen prevalence. Since physical attractiveness is thought to signal health and disease resistance, evolutionary psychologists have predicted that, in societies high in pathogen prevalence, people will value attractiveness more in a mate. Indeed, research has confirmed that pathogen prevalence is associated with preferences for attractiveness across nations. Women in nations with high pathogen prevalence also show greater preferences for facial masculinity. Researchers have also reasoned that sexual contact with multiple individuals increases the risk of disease transmission, thereby increasing the costs of pursuing a short-term mating strategy. Consistent with this reasoning, higher pathogen prevalence is associated with lower national SOI scores. Finally, several studies have found that experimentally manipulating disease salience has a causal influence on attractiveness preferences and SOI scores in predicted directions.
Mating strategies and political attitudes
Some evolutionary psychologists have argued that mating strategies can influence political attitudes. According to this perspective, different mating strategies are in direct strategic conflict. For instance, the stability of long-term partnerships may be threatened by the availability of short-term sexual opportunities. Therefore, public policy measures that impose costs on casual sex may benefit people pursuing long-term mating strategies by reducing the availability of short-term mating opportunities outside of committed relationships. One public policy measure that imposes costs on people pursuing short-term mating strategies, and may thereby appeal to sexually restricted individuals, is the banning of abortion. In an influential doctoral dissertation, the psychologist Jason Weeden conducted statistical analyses on public and undergraduate datasets supporting the hypothesis that attitudes towards abortion are more strongly predicted by mating-relevant variables than by variables related to views on the sanctity of life.
Weeden and colleagues have also argued that attitudes towards drug legalization are driven by individual differences in mating strategies. Insofar as sexually restricted individuals associate recreational drug use with promiscuity, they may be motivated to oppose drug legalization. Consistent with this, one study found that the strongest predictor of attitudes towards drug legalization was scores on the SOI. This relationship remained strong even when controlling for personality traits, political orientation, and moral values. By contrast, nonsexual variables typically associated with attitudes towards drug legalization were strongly attenuated or eliminated when controlling for SOI and other sexuality-related measures. These findings were replicated in Belgium, Japan, and the Netherlands. Weeden and colleagues have made similar arguments and have conducted similar analyses in regard to religiosity; that is, religious institutions may function to facilitate high-fertility, sexually restricted mating and reproductive strategies.