This study Oxytocin Modulates Social Distance between Males andFemales examines the effects of Oxytocin (OXT) on men in monogamous relationships. It demonstrates that OXT assists in maintaining fidelity to that relationship. OXT levels are increased by close and sexual interactions with their partner. The specificity of the OXT effect in influencing the social distance  that males keep from unfamiliar females is evidenced by our finding  that it has no significant effect on the distance kept from unfamiliar  males. Given the absence of PS differences between single and  pair-bonded men in the PLC group, it is clear that for these potential  fidelity-enhancing effects of OXT to be revealed, female partners  would need to evoke its endogenous release immediately before contexts  in which the men might encounter other women. While, compared with  singles, basal concentrations of OXT in blood are increased in couples  during the early stages of romantic love and stay significantly  elevated in couples remaining together 6 months later (Schneiderman et  al., 2012), our results suggest that further augmentation of  endogenous OXT release is necessary to produce fidelity-enhancing  effects. Mechanistically, this may be related to additional OXT either  compensating a relative deficit (optimization hypothesis) or by  collapsing already optimal levels (decompensation hypothesis). While  the most obvious physiological stimulus for promoting endogenous OXT  release in men would be having sex with their mate (Kruger et al.,  2003), the simple close presence and touch of their partner at any  given moment in time might also suffice (Holt-Lunstad et al., 2008).  Thus, OXT effects in promoting monogamy in males may normally depend  upon the presence of a close positive relationship in the bond with  their female partners and close physical proximity between the couple.1There have been studies on the factors involved in  sexual infidelity.Virtually all American couples, married or cohabiting, expect sexual  exclusivity of one another. This article asks why some people are  sexually exclusive while others have sex with someone besides their  mate. Previous research has linked personal values, sexual  opportunities, and quality of the marital relationship to extramartial  sex. This paper integrates these findings in a multivariate model that  incorporates factors informing sexual decision making as well as  demographic risk factors. Nationally representative survey data show  higher likelihood of sexual infidelity among those with stronger  sexual interests, more permissive sexual values, lower subjective  satisfaction with their union, weaker network ties to partner, and  greater sexual opportunities. With these factors controlled, gender  differences are substantially reduced or eliminated, although racial  effects persist. 2 Given that there are people who can maintain close relationships, simultaneously, with more than one partner.Have there been studies examining the  brain biochemistry  that increases  an individual's propensity for sexual infidelity? 1 Oxytocin Modulates Social Distance between Males and FemalesDirk Scheele1, Nadine Striepens1, Onur Gntrkn, Sandra Deutschlnder, Wolfgang Maier1,  Keith M. Kendrick, and Ren Hurlemann The Journal of Neuroscience, 14 November 2012, 32(46): 16074-16079; doi: 10.1523/JNEUROSCI.2755-12.20122 Sexual Infidelity Among Married and Cohabiting AmericansJudith Treas1, Deirdre Giesen2Article first published online: 2 MAR 2004DOI: 10.1111/j.1741-3737.2000.00048.
Studies linking brain chemistry to sexual infidelity
neurobiology;sexuality
The number one hormonal suspect in infidelity has been testosterone. Partially this has been predicted because testosterone predicts sex drive in both men and women. The problem with testing this one in actual humans though is that most of the things associated with cheating also cause increased testosterone levels (flirting, increased number of sexual partners). Therefore, there's a serious chicken and egg problem in more observational studies.Roney, J. R., Simmons, Z. L., & Lukaszewski, A. W. (2010). Androgen receptor gene sequence and basal cortisol concentrations predict mens hormonal responses to potential mates. Proceedings of the Royal Society of London B, 277, 57-63.