What makes us jealous depends on the type of unfaithfulness. 

By Grace Elkus
Updated October 08, 2015
couple fighting
Credit: Yo Oura/Getty Images

Jealousy is an obvious reaction to infidelity—but what triggers this emotion can differ greatly between men and women.

While a man is more likely to get riled up if his partner has a one-night-stand, a woman tends to get more jealous if her partner becomes emotionally invested in another woman, according to a new study conducted by evolutionary psychologists at the Norwegian University of Science and Technology and the University of Texas.

More than one thousand people participated in the study by filling out one of four versions of a questionnaire that described four different infidelity scenarios.

Half of the participants were asked to gauge whether emotional or sexual infidelity was most upsetting to them, while the other half used a rating system to evaluate the scenarios, which in their case had already been described as either emotional or sexual.

Although researchers expected some discrepancy in the responses, they were surprised by how strong the differences were. Men were significantly more jealous of sexual infidelity, while women were much more affected by emotional cheating. Relationship status and prior experiences with infidelity did not have a significant impact on the results.

"As in two of our previous studies, we found clear sex differences in the jealousy responses among those who had to choose which aspect of infidelity was most upsetting to them,” Mons Bendixen, associate professor from the Norwegian University of Science and Technology and one of the study’s authors, said in a statement.

The results support the evolutionary psychology perspective, which maintains that over time men and women have adapted differently to reproduction challenges, including infidelity. Because men struggle with paternal insecurity (and must decide whether they are really the father of their partner’s child), their jealousy is a reaction to threats of sexual cheating.

Women, on the other hand, have had to ensure that their partner will provide for their child and, therefore, a man spending time and resources on other women became an even greatest threat than physical infidelity.

"The cultural gender role perspective believes that jealousy is learned, but we feel confident that these reactions are mechanisms that are part of an evolved human mind, given comparable findings across several nations," said Bendixen.