Sexual jealousy is a special form of jealousy in sexual relationships, based on suspected or imminent sexual infidelity. The concept is studied in the field of evolutionary psychology.

Basis Evolutionary psychologists have suggested that there is a gender difference in sexual jealousy, driven by men and women's different reproductive biology. The theory proposes that a man perceives a threat to his relationship's future because he could be fooled into raising children that are not his own. In contrast, a woman risks losing to another the relationship and all the benefits that entails. Research has shown that men are impacted more by sexual infidelity, while women are more impacted by emotional infidelity.

An alternative explanation is from a social-cognitive perspective. Typically, men place importance on their masculinity and sexual dominance. When the male's partner commits sexual infidelity, these two components of his ego become severely threatened. Women are more emotionally invested in a relationship, and therefore experience a threat to their self-perception when a partner commits infidelity, more concerned with risk to the emotional content than the sexual.

Some research has suggested that there are no gender differences in sexual jealousy, concluding that males and females both equally experience distress over emotional and sexual infidelity. Sexual jealousy is cross-culturally universal but how it manifests itself may differ across cultures.

Gender-specific behaviors Female

Psychologists have found that males react very strongly to sexual infidelity, whereas females are more likely to forgive a one-time sexual adventure if it does not threaten the male parental investment. Therefore, jealousy is likely to be evoked in females if they feel that their partner may leave them for another woman; this has been shown to be more likely to occur if the male commits emotional infidelity. Emotional infidelity occurs when one partner develops a meaningful, emotional attachment with someone outside of their primary romantic relationship.

Emotional jealousy Many studies have shown that females tend to place a stronger emphasis on the emotional aspect of infidelity over the sexual aspect; it is this emotional infidelity that becomes the focus of female sexual jealousy. The most direct evidence for female's focus on emotional jealousy comes from Buss et al. (1992) who presented participants with scenarios in which they were asked to choose between a partner's sexual unfaithfulness and a partner's emotional unfaithfulness as the most distressing event. They found that more females than males reported a partner's emotional infidelity as the most distressing event. As well as using self-report measures, the researchers measured the participants' physiological responses (heart rate and electrodermal activity) to the scenarios; women were also found to be more physiologically upset to the idea of their partners committing emotional infidelity.

Male

Male sexual jealousy functions to defend paternity confidence, and is likely to have evolved through natural selection to prevent cuckoldry — a threat to males since they risk expending resources to support the biological offspring of others. The male reaction stereotypically manifests as the emotion of jealousy, using or threatening violence to protect sexual exclusivity, and thus the inclination to control women. This idea of males ensuring sexual exclusivity has also led to laws on adultery.

From an evolutionary perspective, sexual jealousy arises from this threat of investing in non-biologically related offspring and thus is most strongly felt over their mate's sexual infidelity than their emotional infidelity. It can take several forms in behaviour: aggression and violence, and possessiveness or controlling behaviour towards their mate. In some cases, sexual jealousy can lead to uxoricide. Threats to a relationship can arise from other sources too, such as the presence of rivals, cues to infidelity, and partner dissatisfaction with the relationship. Morbid jealousy is also concurrent with male sexual jealousy – an obsession with thoughts of a partner's suspected sexual infidelity. A 2012 meta-analysis found that sexual jealousy in males can also lead to emotions such as distress, hurt and disgust being experienced.

Expression

Expression in females

Aggression While most empirical research suggests that males are more likely to act aggressively in response to sexual jealousy, some studies have shown that females may also display aggression and violence.

Women have been found to report that their hypothetical sexual jealousy would manifest itself as anger and physical aggression towards the man. It has been suggested that this is because women are more empathetic towards the "victim", triggering strong aggression towards the unfaithful man. However, it is not known if these hypothetical reports would become actions in real life situations. On the other hand, research shows that women are as likely to be violent in intimate partnerships as men, in contrast to society at large.

Because it is the woman who ultimately chooses the mate, aggression caused by infidelity may be directed at the rival female. As a result, when a woman is around a suspected rival female, she may be more likely than a male counterpart to announce that her companion is "taken" and go out of her way to enhance her appearance to her spouse.

Self-blame Following infidelity, women are more likely to focus their sexual jealousy on their own relationship and self-blame. They are also more likely to experience symptoms of depression following the infidelity. Evidence for the interpretation that in jealousy situations women focus more on their own functioning as a partner comes from research by Dijkstra and Buunk (2002). This research suggests that unlike men's jealousy, women's jealousy stems more from comparing their own qualities with those of the rival. The higher the level of social comparison, a personality characteristic referring to the tendency to compare one's characteristics with those of others, the more jealousy various rival characteristics evoked.

Expression in males

Mate guarding behaviour

One form of male sexual jealousy is mate guarding. This tactic is used to prevent partner infidelity and thus may be used when there are perceived threats in the environment. It results in several behaviours, and researchers have documented up to 19 tactics used. This includes (but is not exclusive to): Violence (or at least hostility) directed towards competitors, Taking up all of the mate's time so that they have no time to meet other potential mates, Emotionally manipulating their mate, Increase their possession signals with jewelry, clothing, cars, etc., Enhancing their appearance (e.g. fixing their hair, clothing, etc.).

Attachment style According to attachment theory, the quality of a child's interactions with caregivers during times of need shape their future interactions; this includes later relationships. Research has shown that insecure-avoidant individuals tend to report more sexual jealousy than those who are securely attached. This may be due to the fact that, in comparison to securely attached individuals, those who are insecurely attached tend to experience lower levels of trust, intimacy and stability in their romantic relationships. Evidence suggests that people who experience low self-esteem are much more afraid that their partner is dissatisfied and being unfaithful, which again increases the likelihood that they will experience sexual jealousy.

Sex drive Sex drive, also known as libido, is the physiological need for sexual activity. Sex drive has been found to be a significant predictor of higher sexual jealousy in both men and women; those who had a higher sex drive showed greater distress at the idea of their partner committing sexual infidelity. This is consistent with other empirical research that has shown that individuals who value sexual gratification highly were more likely to be distressed by sexual infidelity. To explain this finding, researchers have suggested the key threat that sexual infidelity poses for individuals with a high sex drive is loss of access to sexual gratification, as their partner is granting sexual access to a third person.

Relationship quality Research has shown that individuals who reported high jealousy scores had more stable and successful relationships than individuals who reported comparatively low jealousy scores. Furthermore, individuals in committed relationships tend to experience higher levels of jealousy than individuals in less committed relationships. To explain this, researchers have proposed that those in better quality, more committed relationships would have more to lose if their partner were to leave them for someone else, and therefore worry more about infidelity. Therefore, such individuals experience greater sexual jealousy if they feel the relationship is threatened.

Explanations Researchers have proposed a number of theories to explain sexual jealousy in both males and females. In addition, some of these explanations can be used to explain the sex differences in sexual jealousy and why there may be differences in the degree to which people experience jealousy.

Evolutionary psychology perspective

Evolutionary psychologists propose that the core function of sexual jealousy is to retain access to a valuable mate. This explanation is known as jealousy as a specific innate module, "JSIM". According to this perspective, sexual jealousy should be activated by threats to the relationship; in particular, threats of sexual infidelity by the female and threats that the male may share his resources (money, protection, or time) with another woman. For males, their biggest concern when they commit to a relationship is ensuring that any offspring produced is biologically theirs, therefore, sexual infidelity is a huge threat to them as there is then a chance that they are not the genetic parent. If a male raises a child that is not genetically his own, he has effectively wasted his resources raising another man's child who will not pass on any of his genes.

As women have genetic certainty when they bear a child, this is not a concern to them. However, they do face a different evolutionary problem. If the woman's partner becomes emotionally attached to another woman, there is a real chance that the male may share his resources with the other woman or leave their current relationship altogether. Either way, the female loses some of the male parental investment, and the loss of her mate's resources may significantly reduce the survival of herself and her offspring.

The evolutionary psychology perspective has been supported by a study conducted by David Buss. He observed that male sexual jealousy is triggered by sexual infidelity, whereas female sexual jealousy is triggered by emotional infidelity. The study concluded that sexual jealousy may be an adaptive function that is triggered in order to retain access to a valuable mate.

Researchers David Buss and Todd Shackleford propose and test several hypotheses about sexual jealousy: Men will devote more resources to mate retention when their partner is younger than them than men whose partner is older than them. This hypothesis rests on the evolutionary principle of mate value. Younger women are likely to have more mate value because they are more fertile. Therefore, it is predicted that men are likely to engage in mate retention behaviours more often when their partner is younger rather than older than them.