Men and women find it unacceptable if their partner is unfaithful. Research even shows that men and women are jealous equally often, and with the same intensity. Yet there are differences between men and women in what they consider the worst-case scenario of their partner’s infidelity. For example, it is worst for a man if his wife has sex with another man, while a woman finds it worse if their husband commits emotional infidelity with another woman than sexual infidelity.
Experimental research into jealousy
Men and women are equally often and to the same extent jealous of their partner’s infidelity. However, further research into jealousy among the different sexes found an interesting difference. Women indicated that they found it worse if their husband was sexually unfaithful than if their husband had a strong emotional bond with another woman (1). Eighty-three percent of women surveyed said they found sexual infidelity worse than emotional infidelity, while only seventeen percent said the opposite. It was different for men: sixty percent said they thought sexual infidelity was worse, and forty percent thought emotional infidelity was worst.
Physiological measurements confirmed this sex difference. A group of men and women were asked to alternately imagine sexual and emotional infidelity. While they did this, skin conductance (which is related to perspiration) and degree of frowning were measured. These two measurements are a reliable indicator of stress. In men, the stress was significantly greater when experiencing sexual infidelity. For women this was exactly the other way around.
Explanations from evolution
These results are surprising at first glance. However, evolutionary psychologists have an explanation for the sex difference. According to their hypothesis, the difference in jealousy between men and women can be traced back to evolution. Within evolutionary theory, the most important mechanisms are the maintenance and transmission of genes. To do this it is of utmost importance to survive, reproduce, and protect and help the offspring survive.
For men, one of the greatest possible dangers was (and is) that they invest their time, effort and possessions in genes that are not their own. Because a man cannot always be one hundred percent sure that he is the biological father of the children he raises, protects and invests in, it is very important for him that his wife is not sexually unfaithful to him. He then runs the risk of raising a child who does not carry his genes.
Women, on the other hand, always know with one hundred percent certainty that they are the biological mother of their children. Sexual infidelity on the part of their partner is of course very undesirable, but in principle it does not have to mean more than a one-off event. In other words, it didn’t have to mean losing her husband. Emotional infidelity, on the other hand, could during evolution (and actually still does) mean a loss of male protection and investment, which was one of the greatest dangers to the maintenance of female genes.
An alternative psychological explanation
Psychologists DeSteno and Salowey (2) have presented arguments against this evolutionary explanation. According to them, sexual and emotional infidelity are strongly linked. People often form emotional relationships with those they have sex with, and vice versa. According to these psychologists, the gender difference in jealousy can be explained by the fact that men and women differ in how they view this connection between sexual and emotional relationships.
Women are more likely to think that their man is capable of having sex without having emotional feelings for the other woman. However, if a man has an emotional relationship with a woman, there is a very good chance that he will also enter into a sexual relationship. According to this view, for women, emotional infidelity from their husbands is even worse than just sexual infidelity.
Men would think that a woman can easily enter into an emotional relationship with another man without having sex with him. However, if she has sex with another man, she will almost certainly also have an emotional relationship with him, because in their view women will not easily have sex without having emotional feelings for a man. This means that sexual infidelity on the part of women is even worse than just emotional ones.
Although the debate between these two different explanations continues to this day, there is considerably more experimental data supporting the evolutionary explanation.