After the
Kinsey Reports came out in the early 1950s, findings suggested that historically and cross-culturally,
extramarital sex has been a matter of regulation more than sex before marriage. The Kinsey Reports found that around half of men and a quarter of women studied had committed
adultery. The
Janus Report on Sexual Behavior in America also reported that one-third of married men and a quarter of women have had an extramarital
affair. Results, however, vary year by year, and also by age-group surveyed. For example, one study conducted by the
University of Washington, Seattle, found slightly, or significantly higher, rates of infidelity for populations under 35, or older than 60. In that study, which involved 19,065 people during a 15-year period, rates of infidelity among men were found to have risen from 20% to 28%, and rates for women ranged from 5% to 15%. A survey conducted in 1990 found that 2.2% of married participants reported having more than one partner during the past year. In general, national surveys conducted in the early 1990s reported that between 15 and 25% of married Americans reported having extramarital affairs. People who had stronger sexual interests, more permissive sexual values, lower subjective satisfaction with their partner, weaker network ties to their partner, and greater sexual opportunities were more likely to be unfaithful. Rates of infidelity among women are thought to increase with age. In one study, rates were higher in more recent marriages, compared with previous generations. Men were found to be only "somewhat" more likely than women to engage in infidelity, with rates for both sexes becoming increasingly similar. Research on pregnancy and its effects on
sexual desire and rates of infidelity conducted in southern Spain indicated that men were more likely to engage in infidelity while their partner was pregnant. It was estimated that 1 in 10 fathers-to-be engaged in infidelity at some point during their partner's pregnancy and suggested that the likelihood of the man engaging in infidelity increases as the woman's pregnancy progresses through its
trimesters. One measure of infidelity is
paternal discrepancy, a situation that arises when someone who is presumed to be a child's father is in fact not the biological parent. Frequencies as high as 30% are sometimes assumed in the media, but research by sociologist Michael Gilding traced these overestimates back to an informal remark at a 1972 conference. The detection of paternal discrepancy can occur in the context of medical
genetic screening, in genetic family name research, and in immigration testing. Such studies show that paternal discrepancy is, in fact, less than 10% among the sampled
African populations, less than 5% among the sampled
Native American and
Polynesian populations, less than 2% of the sampled
Middle Eastern population, and generally 1–2% among
European samples. These differences have been generally thought due to evolutionary pressures that motivate men towards sexual opportunity and women towards commitment to one partner (for reasons such as reproductive success, stability, and social expectations). In addition, recent research finds that differences in gender may possibly be explained by other mechanisms including power and sensations seeking. For example, one study found that women in more financially independent and higher positions of power, were also more likely to be more unfaithful to their partners. In another study, when the tendency to sensation seek (i.e., engage in risky behaviours) was controlled for, there were no gender differences in the likelihood to being unfaithful. Those that posit a sex difference exists state that men are 60% more likely to be disturbed by an act of sexual infidelity (having one's partner engage in sexual relations with another), whereas women are 83% more likely to be disturbed by an act of emotional infidelity (having one's partner fall in love with another). From an evolutionary perspective, men are theorized to maximize their
fitness by investing as little as possible in their offspring and producing as many offspring as possible, due to the risk of males investing in children that are not theirs. Women, who do not face the risk of cuckoldry, are theorized to maximize their fitness by investing as much as possible in their offspring because they invest at least nine months of resources towards their offspring in pregnancy. A common way to test whether an innate jealousy response exists between sexes is to use a forced-choice questionnaire. This style of questionnaire asks participants "yes or no" and "response A or response B" style questions about certain scenarios. For example, a question might ask, "If you found your partner cheating on you would you be more upset by (A) the sexual involvement or (B) the emotional involvement". Many studies using forced choice questionnaires have found statistically significant results supporting an innate sex difference between men and women. Although forced-choice questionnaires show a statistically significant sex-difference, critics of the theory of evolved sex differences in jealousy question these findings. In consideration of the entire body of work on sex differences, C. F. Harris asserted that when methods other than forced-choice questionnaires are used to identify an innate sex difference, inconsistencies between studies begin to arise. For example, researchers found that women sometimes report feeling more intense jealousy in response to both sexual and emotional infidelity. The results of these studies also depended on the context in which the participants were made to describe what type of jealousy they felt, as well as the intensity of their jealousy. In her meta-analysis, Harris raises the question of whether forced choice questionnaires actually measure what they purport: jealousy itself and evidence that differences in jealousy arise from innate mechanisms. For example, more men are reported to have an insecure, dismissing avoidant attachment style; where these "individuals often attempt to minimize or constrict emotional experience, deny needs for intimacy, are highly invested in autonomy, and are more sexually promiscuous than individuals who have other attachment styles". Levy and Kelly (2010) tested this theory and found that adult attachment styles strongly correlate to which type of infidelity elicited more jealousy. A 2015 study found a correlation between
AVPR1A expression and predisposition to
extrapair mating in women but not in men.
Sexual orientation Evolutionary researchers have suggested that humans have innate mechanisms that contribute to why they become sexually jealous, this is especially true for certain types of infidelity. It has been hypothesized that heterosexual men have developed an innate psychological mechanism that responds to the threat of sexual infidelity more than emotional infidelity, and vice versa for heterosexual women Symons (1979) determined that sexual jealousy is the major reason that many homosexual men are unsuccessful in maintaining monogamous relationships Barah and Lipton argue that heterosexual couples may cheat just as much as homosexual relationships. Harris (2002) tested these hypotheses among 210 individuals: 48 homosexual women, 50 homosexual men, 40 heterosexual women, and 49 heterosexual men. Summarizing the findings from these studies, heterosexual men seem to be more distressed by sexual infidelity than heterosexual women, lesbian women, and gay men. ==Responses==