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. Furthermore, statistics on domestic violence continue to show that in relationships it is primarily men who are the abusers, rather than the women. 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