Excerpts from studies regarding promiscuity, sociosexual orientation, and infidelity

[Promiscuity and Infidelity]

In illustration of this, the odds ratio of 1.13 for lifetime sexual partners obtained with the face-to-face mode of interview indicates that the probability of infidelity increased by 13% for every additional lifetime sexual partner,

Predictors of Annual Prevalence of Reported Sexual Infidelity

we evaluated the association between infidelity and sexual experience, as prior studies have found that people with more sexual relationships in the past are more likely to have secondary sex partners (Bozon, 1996).

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Regarding the correlates of infidelity, results indicated that on the basis of both methods of assessment, the probability of sexual infidelity (a) was greater for Blacks (relative to the remainder of the sample), (b) decreased with higher religiosity, (c) increased with higher number of lifetime sexual partners,

Sexual infidelity in a national survey of American women: differences in prevalence and correlates as a function of method of assessment. Mark A. Whisman, Douglas K. Snyder J Fam Psychol. 2007 Jun; 21(2): 147–154. doi: 10.1037/0893-3200.21.2.147

From https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/17605537/citedby/?tool=pubmed

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Our findings demonstrate that infidelity and number of sexual partners are both under moderate genetic influence (41% and 38% heritable, respectively) and the genetic correlation between these two traits is strong (47%).

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Not surprisingly, the average number of sexual partners was significantly higher among respondents who had been unfaithful compared with those who had remained faithful (7.73 vs. 3.78, p < .001). The phenotypic correlation between these traits was .36 (p < .001).

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The resulting genetic correlation between the two traits was .47, so nearly half the genes impacting on infidelity also affect number of sexual partners. The correlation of the unique environment between the two variables was .48.

Genetic influences on female infidelity and number of sexual partners in humans: a linkage and association study of the role of the vasopressin receptor gene (AVPR1A). Lynn F. Cherkas, Elizabeth C. Oelsner, Y. T. Mak, Anna Valdes, Tim D. Spector Twin Res. 2004 Dec; 7(6): 649–658. doi: 10.1375/1369052042663922

From https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/15607016/citedby/?tool=pubmed

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In a world where infidelity and promiscuity are increasingly experienced (Brand et al. 2007, Jones and Paulhus 2012), few studies have focused on their emotional and sexual domains. The infidelity and the promiscuity can have an important impact on individuals and on intimate relationships (Silva et al. n.d., Vangelisti and Gerstenberger 2004). For example, the infidelity is one of the most common reasons for divorce and couple therapy (Glass and Wright 1992). In addition, promiscuity is known to have a negative effect on healthy living (Okafor and Duru 2010).

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Some authors defend that infidelity may come as a consequence of promiscuity, and that frequently both concepts go side by side (Feldman and Cauffman 1999, Mark et al. 2011). Promiscuity can be understood as the willingness to engage in sexual activities with several partners, have casual sex and get involved in sexual activities sooner rather than later (Jones and Paulhus 2012)

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Feldman and Cauffman (1999) analyzed a sample of 417 college students and found that individuals that show permissive behaviors, associated with increased number of sexual partners are more prone to engage in infidelity. Similarly, Barta and Kiene (2005) conducted a study with 432 college students, 120 of whom mentioned past infidelity behaviors. Their results showed that those who have an unrestricted sociosexual orientation tend to report a sexual motive for being unfaithful.

Sexual promiscuity was significantly positively correlated with emotional promiscuity [r(356) = .261, p < .001], as well with sexual infidelity [r(323) = .595, p < .001] and emotional infidelity [r(323) = .676, p < .001], indicating that sexually promiscuous participants also tend to be emotionally promiscuous, and sexual[ly] and emotional[ly] unfaithful.

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In terms of the sexual domain, results showed that there is also a positive correlation between sexual promiscuity and sexual infidelity, stating that individuals that tend to be more sexually promiscuous also tend to be more sexually unfaithful. These results support our second hypothesis.

Pinto, R., & Arantes, J. (2016). The relationship between sexual and emotional promiscuity and infidelity. ATINER’S Conference Paper Series, No. PSY2016–2087, Athens, Greece.

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Bonus Round: Female Infidelity Based on Number of Premarital Sex Partners -- Statistics Brain

• Number of pre-marital partners: percent who cheated once married
• 2: 10.4%
• 3: 14.9%
• 4: 17.7%
• 5: 21.6%
• 6-10: 26.0%
• 11-20: 36.7%
• 21+: 46.8%

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[Unrestricted SOI and infidelity]

Sociosexual orientation, or sociosexuality, is the individual difference in the willingness to engage in sexual activity outside of a committed relationship. Individuals with a more restricted sociosexual orientation are less willing to engage in casual sex; they prefer greater love, commitment and emotional closeness before having sex with romantic partners. Individuals who have a more unrestrictedsociosexual orientation are more willing to have casual sex and are more comfortable engaging in sex without love, commitment or closeness

From https://en.wikipedia.org/wiki/Sociosexual_orientation

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The genetic theory hypothesizes that female sociosexual variation reflects women's "decisions" regarding how much commitment to trade for genetic quality. Women who value commitment much more than male quality have a restricted sociosexual orientation, and women with opposite preferences have an unrestricted orientation. This variation has been hypothesized to be maintained by frequency-dependent selection (Gangestad & Simpson, 1990).

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approximately half of the men and women in the top (withinsex) quintiles of sociosexuality had been sexually unfaithful to a steady partner; this was more than a tenfold increase over the corresponding rate for people in the bottom quintiles. Sexual infidelity is a common cause of divorce cross-culturally (Buss, 1994)

Do individual differences in sociosexuality represent genetic or environmentally contingent strategies? Evidence from the Australian twin registry. J. M. Bailey, K. M. Kirk, G. Zhu, M. P. Dunne, N. G. Martin J Pers Soc Psychol. 2000 Mar; 78(3): 537–545.

From https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/10743879/citedby/?tool=pubmed

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Individuals exhibiting sexually permissive attitudes and those who have had a high number of past sexual relationships are more likely to engage in infidelity (Feldman & Cauffman, 1999). In a study of supposedly exclusive dating couples, it was found that individuals exhibiting an ‘unrestricted’ sociosexual orientation (SO) were significantly more likely to pursue extra-pair involvement (Seal, Agostinelli, & Hannett, 1994). Individuals are said to be unrestricted if they score high on the Sociosexual Orientation Index (SOI). Items on this scale include a question tapping whether the respondent feels that love is a prerequisite for sexual relations with a partner, the number of ‘one-night stands’ a respondent has had, and how many partners he or she hopes to have in the next year (Simpson & Gangestad, 1991).

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A preliminary ANOVA analysis revealed that individuals reporting a past history of infidelity tended to have a greater number of past sexual partners than those without a history of infidelity

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individuals with a history of infidelity, compared with those without, have a relatively unrestricted SO.

Barta, W. D., & Kiene, S. M. (2005). Motivations for infidelity in heterosexual dating couples: The roles of gender, personality differences, and sociosexual orientation. Journal of Social and Personal Relationships, 22(3), 339-360. http://dx.doi.org/10.1177/0265407505052440

From http://psycnet.apa.org/record/2005-07434-003

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Individuals with an unrestricted sociosexual orientation (SO) are less committed to their romantic relationships and more likely to engage in infidelity

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BECAUSE OF THE PREVALENCE and consequences of infidelity (e.g., Vangelisti & Gerstenberger, 2004; Weiderman, 1997), being able to predict extradyadic behavior is important. One known predictor is sociosexual orientation (SO). SO is an individual difference that reflects one’s beliefs and behaviors toward sex and is measured on a continuum ranging from restricted to unrestricted (Simpson & Gangestad, 1991). Those with a restricted SO prefer to engage in sexual behaviors within the context of a close and committed romantic relationship, whereas those with an unrestricted SO do not need a committed relationship in order to have sex. Not surprisingly, an unrestricted SO has been associated with a greater willingness to engage in infidelity when using either self-report (Barta & Kiene, 2005; Ostovich & Sabini, 2004) or behavioral measures (Seal, Agostinelli, & Hannett, 1994). Previous studies have shown that those with an unrestricted SO are generally less committed to their romantic partners (Jones 1998; Simpson & Gangestad, 1991), and low commitment is often a predictor of infidelity (Drigotas, Safstrom, & Gentilia, 1999). Similarly, those with an unrestricted SO are often looking for new, attractive partners (Simpson, Wilson, & Winterheld, 2004).

Thus, it was predicted that SO would be positively related to various types of infidelity, such that individuals with an unrestricted SO would be more likely to engage in the three types of infidelity previously identified by Wilson, Mattingly, Clark, Weidler, and Bequette (2011); Ambigous (e.g., dancing with an extradyadic partner), Deceptive (e.g., lying to one’s partner), and Explicit (e.g., sexual intercourse with an extradyadic partner). Further, this relationship was predicted to be mediated by commitment, such that individuals with an unrestricted SO would have lower commitment, which would in turn lead to an increased likelihood of engaging in infidelity.

Sociosexual orientation, commitment, and infidelity: a mediation analysis. Brent A. Mattingly, Eddie M. Clark, Daniel J. Weidler, Melinda Bullock, Jana Hackathorn, Katheryn Blankmeyer J Soc Psychol. 2011 May-Jun; 151(3): 222–226.

From https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21675178/citedby/?tool=pubmed

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one plausible explanation is that humans actually consist of a mix of short-term (promiscuous) and long-term (monogamous) mating phenotypes. The extent to which any one individual pursues a short-term mating strategy (‘unrestricted’ strategy involving promiscuous mating with multiple partners) or a long-term mating strategy (‘restricted’ strategy favouring the formation of exclusive and extended pair-bonds) has been referred to as their ‘sociosexual orientation’

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We tested the hypothesis that there are distinct mating strategy phenotypes in both men and women using two large datasets: a North American and British sample of 595 individuals who completed the sociosexual orientation inventory (SOI-R) [13] and a British sample of 1314 individuals whose 2D : 4D digit ratios were measured. The SOI-R indexes an individual’s psychological degree of sexual promiscuity on a continuum running from restricted (monogamous) to unrestricted (promiscuous).

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Modelling confirmed the existence of two phenotypes within each sex, one of low (restricted) sociosexuality and the other of high (unrestricted) sociosexuality. High-sociosexuality males make up a slightly larger proportion of the male distribution in each case, and low-sociosexuality females make up a slightly larger proportion of the female distributions (table 1).

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Overall, our results suggest that the proportional split in males slightly favours an unrestricted (short-term) mating strategy, with a 57 : 43 split on average for the three datasets, whereas females have a reversed split (47 : 53). However, the mixing proportions in the 2D : 4D digit ratio dataset suggest that a slightly higher proportion of the unrestricted phenotype is present in both sexes (males approx. 62%, females approx. 50%).

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If the two phenotypes essentially represent stable and unstable pair-bonding predispositions (see Walum et al. [11]), we might expect there to be some tendency for assortative mating between the phenotypes. We might also predict that stable–stable pairings are less likely to divorce than other pairings, with unstable–unstable pairings having the shortest durations. The existence of two phenotypes raises a number of further evolutionary questions.

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Previous research has found that female sociosexuality is more responsive to environmental shifts than male sociosexuality [4,22], and our data confirm this: while both sexes exhibit a shift (towards a restricted strategy in males, but towards unrestricted in females), the magnitude of the shift is larger in women than in men. While there is strong evidence that additive genetic factors best predict adult sociosexuality [23], differences in behaviour are in part likely to reflect cultural or environmental fine tuning of underlying genetic strategies in response to local circumstances as each sex tries to maximize overall fitness.

Wlodarski R, Manning J, Dunbar RIM. 2015 Stay or stray? Evidence for alternative mating strategy phenotypes in both men and women. Biol. Lett. 11: 20140977. http://dx.doi.org/10.1098/rsbl.2014.0977