Many people whose spouse forgives them over infidelity mistrust the signals and do not really believe that they are forgiven, according to Norwegian researchers.
"We have a strong tendency not to believe our partner when they tell us we are forgiven," said Mons Bendixen, associate professor in the Department of Psychology at Norwegian University of Science and Technology.
Once forgiven, you may become more attentive, buy gifts or do other things that you expect your partner will appreciate.
Underestimating the degree of forgiveness is probably an evolutionary mechanism, because the relationship may be in danger.
"The cost could be high if you think you are forgiven, but really are not. You might not work hard enough to mend the relationship," Bendixen added in a paper published in the journal Evolutionary Behavioural Sciences.
Researchers conducted the survey with 92 heterosexual couples.
These were young students who answered questions about imagined sexual or emotional infidelity by their partner and themselves.
According to the findings, when interpreting signals, we can make one of two false assumptions: we can believe that something exists even if it doesn't, and we can believe that something doesn't exist even if it does.
From an evolutionary perspective, it's a question of which errors are more adaptable.
"An example is men who think women are interested in sex, even though the women's intention is just to be nice. The most important thing for men in situations like this is not to miss a sexual opportunity," Bendixen noted.
Most partners aren't particularly intent on getting revenge or seeing their partner suffer.
That doesn't mean that it never happens, but the probability is the same for both sexes.
They are more likely to pull away and want to keep some distance.
"Partners want the infidelity to have a cost, but will rarely respond by being unfaithful themselves," added evolutionary psychologist Trond Viggo Grontvedt.
There is also no difference between the sexes when it comes to whether they would break up with the unfaithful partner or not. This is as likely for women as for men.
The sexes agree on a lot when it comes to infidelity. But one exception exists.
"Men often do not understand how hard emotional infidelity is on women," said Professor Leif Edward Ottesen Kennair in the Department of Psychology.
Sexual infidelity strongly affects both men and women. Neither men nor women usually find it acceptable for their partner to have sex outside the marriage.
Men who are confronted with emotional infidelity do not necessarily think that they have done anything wrong, researchers said.
Men have less need to distance themselves from their partner than women do, and they look at emotional infidelity as less threatening to the relationship than women do, the findings showed.