Both men and women view a partner’s financial investment in a rival as a major relationship threat

A recent study published in the journal Evolution and Human Behavior suggests that people experience the strongest romantic jealousy when they watch their partner give resources to a potential rival, regardless of gender. The findings provide evidence that giving away resources is viewed as a serious relationship threat by both men and women. This research highlights how our emotional alarm systems react more strongly to a partner’s active investment in someone else rather than a partner passively receiving attention.

Scientists initiated this research to test traditional evolutionary ideas about human mating in a more realistic setting. Evolutionary theory proposes that men and women face different historical challenges when it comes to reproduction and survival. For early human men, a partner’s sexual infidelity posed a risk of unknowingly raising another man’s child.

For early human women, a partner’s emotional infidelity threatened the loss of time, protection, and resources for their own children. Because of these different historical pressures, scientists suspect that modern men and women might trigger jealousy in slightly different ways. Men are often expected to be more reactive to cues of sexual interest from rivals, while women are expected to be more reactive to cues of emotional investment or resource sharing.

Most past research on this topic relied on simple surveys asking people to imagine hypothetical cheating scenarios. Scientists wanted to move beyond these imaginary situations and observe actual behavior in a controlled environment. “The aim was testing if romantic jealousy could be evoked with economic game paradigms in couples, to extend what is universally found using the classical forced choice hypothetical sexual and emotional infidelity scenarios,” explained lead researcher Ana María Fernández, a professor at the University of Santiago de Chile.

They designed an interactive experiment involving real money to see if financial decisions could mimic the ancient threats of resource loss and mate poaching. Mate poaching is a term used in psychology to describe situations where a person intentionally tries to attract someone who is already in a committed relationship. “As an experimental psychologist, this allowed me to extend mind-based methods to the use of experimental economics as a proxy for jealousy inducement,” Fernández noted.

To test these ideas, the researchers recruited 79 heterosexual couples for a laboratory experiment. This resulted in a total of 158 individual participants. The participants were around 30 years old on average and had been in their current relationship for at least six months.

The couples arrived at the lab together but were seated in the same room separated by a physical partition. They then played a computer-based financial exercise known as a dictator game. In a standard dictator game, one person is given a set amount of money and decides how to split it with another person, who has no choice but to accept the offer.

In this modified version, participants believed they were interacting online with their real-world partner and an opposite-sex stranger. The stranger acted as a potential romantic rival. After each round of the game, participants rated their feelings of jealousy on a scale from one to five.

The researchers created two main experimental scenarios. In the investment scenario, participants watched their partner give 75 percent of the available money to the rival, keeping only 25 percent for the participant. This was designed to trigger female jealousy by mimicking a partner diverting resources to another woman.

In the receiving scenario, participants watched their partner receive a large sum of money from the rival. The partner actively accepted these resources. This was designed to trigger male jealousy by mimicking a rival attempting to steal the partner away.

The data revealed that the investment scenario caused the highest levels of jealousy for all participants. Both men and women felt highly threatened when their partner actively gave money to a rival. “We found that a romantic partner allocating more resources to a stranger than oneself is a situation that produces jealousy, regardless of gender,” Fernández said.

The researchers noted that actively giving money requires thought, intention, and sacrifice. Because of this, both men and women interpreted the investment scenario as a major warning sign of a partner slipping away. The anticipated gender differences did not fully emerge in the receiving scenario.

The researchers predicted that men would become much more jealous than women when their partner received money from a rival. Instead, men and women displayed very similar, relatively low levels of jealousy in this situation. “We got a weaker effect when trying to model male jealousy by the partner receiving resources from an opposite sex stranger, although we made it explicit that the partner accepted these resources,” Fernández explained.

The scientists noted that passively receiving money might not send a strong signal of sexual betrayal. A partner might accept resources from a rival just to gain a free benefit, which does not necessarily mean they are sexually interested in the rival. To ensure the jealousy was specifically about their own romantic relationship, the researchers also included several control scenarios.

In these control rounds, participants watched random strangers give or receive money. By including these extra scenarios, the scientists could verify that the jealousy stemmed from a direct threat to the participant’s own romantic bond. “Other than the generalized jealousy at third-party allocation, we found that some of the control conditions indicate that jealousy was not elicited simply by observing unequal allocations or interactions with opposite-sex others,” Fernández pointed out.

She added that the feeling was very specific to relationship threats. “Rather, jealousy was strongest when the resource movement carried a clear relational threat: for women, the partner’s allocation of resources to a female rival,” Fernández observed. A subtle gender difference did appear during the control scenarios.

Women reported feeling jealous when they watched any committed man give money to a single woman, even if that man was a total stranger. This provides evidence that women might be generally more vigilant about the ways men distribute resources, treating it as a broad social warning sign. Finally, individual personality traits played a significant role in the emotional reactions.

The scientists asked participants to complete questionnaires about their personal relationship insecurities. These questionnaires measured digital jealousy, which is the anxiety people feel about their partner’s online interactions. They also measured attachment anxiety and attachment avoidance.

Attachment anxiety refers to a deep fear of abandonment and a constant need for reassurance. Attachment avoidance describes a tendency to push others away to stay emotionally independent and avoid vulnerability. People who scored high in digital jealousy and attachment anxiety experienced much more jealousy across all the different game scenarios.

This suggests that a person’s natural disposition greatly influences how intensely they react to relationship threats. While this experimental design offers a fresh perspective on romantic emotions, it does have some limitations. The laboratory setting and the exchange of small amounts of money might not fully capture the intense pain of a real-world betrayal.

Participants might also have adjusted their answers to appear more socially acceptable on the self-reported surveys. Additionally, the sample consisted mostly of young, educated, and heterosexual couples. This limits how well the findings can be applied to older adults, different cultural groups, or non-heterosexual relationships.

Improving the experimental conditions is a priority for the research team. “I would like to improve the condition of reception of resources from a third party, to conclude whether this can be modeled and replicated from the literature on sex differences in jealousy,” Fernández said. Tracking couples over a longer period of time could also help explain how jealousy changes as relationships mature.

The study, “Resource allocation and romantic jealousy: An experimental test of sex differences using economic games“, was authored by Ana María Fernández, María Teresa Barbato, Michele Dufey, Belén Zavalla, and María Luíza Rodrigues Sampaio de Souza.