Jealousy, by the numbers: money as a lie detector

A recent study published in the journal Evolution and Human Behavior put one of humanity's oldest emotions — jealousy — under the microscope, and unexpectedly found its perfect trigger: money. It turns out that, regardless of gender, people feel the strongest pangs of jealousy when they see their partner give resources to a potential rival. Yes, not a glance or a message, but the most ordinary bank transfer or generous gift can turn a romance into a thriller.

The researchers set out to test old evolutionary theories on new ground. The classic story goes like this: for ancient men, a wife's sexual infidelity meant the risk of raising another man's child (and where's the saving of resources in that?), while for women, a husband's emotional infidelity threatened the loss of bread, protection and attention for their offspring. Over time, these scenarios mutated like a virus into expectations: men should be especially afraid of sexual infidelity, while women should be wary of emotional spending and sharing resources.

But most previous studies relied on simple questionnaires about imagined affairs. So the team brought 79 heterosexual couples (158 people, around 30 years old on average and together for at least six months) into a lab and staged a money-based reality show. No suggestive messages, just cold calculation: in a computer game, one partner could give a sum of money to an unknown person of the opposite sex, then rate their jealousy on a scale from 1 to 5.

There were two scenarios. First: your partner gives 75% of the sum to a rival (a simulation of "resource diversion" — the classic female jealousy trigger). Second: your partner RECEIVES money from a rival (a simulation of "competitor courtship" — the classic male source of worry). After each round came a questionnaire: who was burning green with jealousy?

It turned out that "giving" was the undisputed champion at triggering jealousy: both men and women get nervous when their partner gives something to someone else of their own accord. It's simple: if you're spending your own money, you must have some shady thoughts. By contrast, "receiving" money caused only a mild itch in both sexes — well, who knows, maybe it was just a windfall?

Women were on alert even when money from another man went to another woman: the social radar is always on. The authors also studied digital jealousy (distress over a partner's online activity) and attachment styles: anxious (panic that they'll leave and never come back) and avoidant (better to keep your distance). The higher the anxiety, the stronger the bursts of jealousy.

Of course, there were a few "buts": a lab is not real life, small sums are no match for losing a flat or a country house, and participants may have prettified their answers to save face. Besides, nearly all of them were young and well-educated. The research will continue: the scientists plan to test their hypotheses, change the scenarios and follow couples for longer to understand how jealousy evolves over time.

The article "Resource allocation and romantic jealousy: An experimental test of sex differences using economic games" was written by a group of researchers from the University of Santiago de Chile.