One measure of infidelity among couples is the frequency of children secretly conceived with a different partner, leading to "non-paternities".
For example, one study found that some women in more financially independent and higher positions of power, were also more likely to be more unfaithful to their partners.
These findings suggest there may be various factors that might influence the likelihood of some individuals to engage in extradyadic relationships, and that such factors may account for observed gender differences beyond actual gender and evolutionary pressures associated with each.
Correspondingly, monogamy and commitment are more commonplace.
On the other hand, when people live within environments that encompass little stress and threats to the viability of offspring, the need for serious and committed relations is lowered and therefore promiscuity and infidelity are more common.
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.
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.
In marital relationships, exclusivity expectations are commonly assumed although they are not always met.
When they are not met, research has found that psychological damage can occur, including feelings of rage and betrayal, lowering of sexual and personal confidence, and damage to self-image.
In terms of infidelity, the theory states that when sex-ratios are high, men are more likely to be promiscuous and engage in sex outside of a committed relationship because the demand for men is higher and so this type of behaviour, which is desired by men, is more accepted.