Article uses three citation styles: inline footnotes, a "references section" and a "further reading" section. For example, the first citation, Leeker & Carlozzi, points to the further reading section. Infidelity (synonyms include: cheating, adultery (when married), netorare (NTR), being unfaithful, or having an affair) is a violation of a couple's assumed or stated contract regarding emotional and/or sexual exclusivity.

The second citation (Weeks) is both defined in text and pointed at using a footnote. Other scholars define infidelity as a violation according to the subjective feeling that one's partner has violated a set of rules or relationship norms; this violation results in feelings of sexual jealousy and rivalry.

Support for this theory comes from evidence showing higher divorce rates in countries with lower sex ratios and higher monogamy rates in countries with higher sex ratios.

Differences in sexual infidelity as a function of gender have been commonly reported.

One measure of infidelity is covert illegitimacy, a situation which arises when someone who is presumed to be a child's father (or mother) is in fact not the biological father (or mother).

Frequencies as high as 30% are sometimes assumed in the media, but research Such studies show that covert illegitimacy 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.

Depending on the context, men and women can experience social consequences if their act of infidelity becomes public.

The form and extent of these consequences are often dependent on the gender of the unfaithful person.In general, national surveys conducted in the early 1990s reported that between 15-25% of married Americans reported having extramarital affairs.Treas and Giesen found that 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.Studies suggest around 30–40% of unmarried relationships and 18–20% of marriages see at least one incident of sexual infidelity.Rates of infidelity among women are thought to increase with age.In marital relationships, exclusivity expectations are commonly assumed although they are not always met.