Scientists use economic game to reveal sex differences in jealousy triggers

Jealousy is triggered in response to real-world cues of resource allocation in romantic relationships, according to a new study published in Evolutionary Psychology.

Jealousy is considered to be a protective emotion, emerging early in childhood and evolving as a way to defend important social relationships from perceived threats. In romantic contexts, researchers have observed distinct patterns in how men and women respond to potential threats. Evolutionary theories propose that jealousy evolved differently in men and women due to reproductive asymmetries, with women being more sensitive to losing a partner’s resources, while men are attuned to cues of sexual infidelity that threaten paternity certainty.

María Teresa Barbato and colleagues explored whether these sex differences in jealousy could be triggered through economic decisions involving real partners. By adapting a modified version of the dictator game, a common tool in behavioral economics, the researchers investigated whether observing a partner allocate or receive money from a potential rival would differentially elicit jealousy in men and women.

The researchers recruited 56 heterosexual couples (112 participants in total), with an average age of 23.5 years and average relationship duration of approximately 33 months. Participants were invited to a lab setting, where they sat apart from their partners and completed an online protocol via Qualtrics. Each individual completed a sociodemographic survey and psychological scales measuring general trust and different dimensions of jealousy (reactive, anxious, and possessive).

Participants were then introduced to a pre-game allocation task to familiarize them with the dictator game, where a fixed amount of money is distributed between two people. Next, participants were randomly shown one of two experimental conditions. In the “investing” condition, they were told their partner had allocated $100 to an opposite-sex stranger and only $30 to them.

In the “receiving” condition, they were told a same-sex stranger gave $100 to their partner and only $30 to that stranger’s own partner. The experimental design allowed each person to play the role of both observer and participant in these scenarios, with sex and condition (invest vs. receive) serving as the primary factors of interest.

After reading the outcome, participants rated their level of jealousy on a scale from 1 (none) to 5 (extreme), as well as other emotions like happiness or indifference. Following the game, a debriefing explained the deception, with support offered by a psychologist if needed.

Women reported significantly more jealousy than men when observing their partner invest money into a potential female rival. They also reported greater jealousy when comparing this investing condition to the receiving condition, where their partner received money from a rival. These findings support the evolutionary hypothesis that women are especially sensitive to cues suggesting their partner may divert resources to another woman, reflecting fears of lost support or emotional commitment. Although men showed a slight increase in jealousy when their partner received money from another man, this effect was not statistically significant.

Across all participants, the act of the partner investing resources in a rival provoked stronger jealousy than receiving resources from one, suggesting that active diversion of support was more emotionally impactful than passive receipt. Individual differences in jealousy traits, particularly reactive and anxious jealousy, amplified the emotional responses to the scenarios.

Other factors such as trust in the partner, age, socioeconomic background, and relationship length did not significantly influence how jealous participants felt.

Of note is that the jealousy-evoking manipulation may not have adequately simulated the core cues of sexual infidelity for men, limiting the ability to fully engage their evolved jealousy mechanisms. Additionally, the relatively small sample size and lack of rival characteristics (e.g., attractiveness) may constrain the generalizability of the results.

The study, “Jealousy as Predicted by Allocation and Reception of Resources in an Economic Game,” was authored by María Teresa Barbato, Ana María Fernández, Carlos Rodriguez-Sickert, José Antonio Muñoz, Pablo Polo, and David Buss.