The Fallacy That Keeps People in Unhappy Relationships

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Psychologist, Nobel Prize winner, and best-selling author Daniel Kahneman has investigated how spooked people are about loss. In his classes, he likes to make an offer to students: “I’m going to toss a coin, and if it’s tails, you lose $10. How much would you have to gain on winning in order for this gamble to be acceptable to you?” Inevitably, people want a reward of $20 or more in order to take the bet. There’s an evolutionary argument for this loss aversion: Organisms that favored avoiding threats over maximizing gains were more likely to hand their genes down to us.

This helps explain why people are so reluctant to give up what they have, even if what they have isn’t the best thing for them. It’s called the “sunk cost fallacy” or the “sunk cost effect.” Psychologists say this occurs when “a prior investment in one option leads to a continuous investment in that option, despite not being the best decision.”

In poker, it’s when you keep betting on a hand that’s going to lose because you’ve already bet too much. In business, it’s when you’ve already spent some large amount of time or money on a project, so you’re hell-bent on completing it. And in love, it’s when people stay in unhappy relationships even when they should get out.

According to a new study in Current Psychology, it’s a pretty standard line of reasoning. Written by Sara Rego and two of her fellow psychologists at the University of Minho in Portugal, the study presented hypothetical situations to people.

In the first hypothetical situation, 951 participants recruited from the university’s institutional email read descriptions of four different relationship conditions before being asked to decide if they should stay in an increasingly sexless, hostile marriage of ten years or end it.

People in the time condition read of a one-year marriage instead of a decade; money that you bought a house together; effort that you had “made a huge effort” to change the situation by providing more attention and showing up with surprises and the like; and a control. About 25 percent of the control and time responses said they’d stay in the relationship, compared to 35 percent in the effort and money conditions.

The second study was slightly different in approach with a total of 275 people recruited from their university. Rather than giving four scenarios, there were just two: a control, where it’s a ten-year relationship (“Imagine that you have been married for the past ten years with your partner”), and an experimental, where it’s only one year. Instead of a dichotomy, participants marked how long they’d stay in by the edges of a ruler, with one end labeled “no time” and the other “a lot of time,” then they noted how many days, months, or years that stood for. Interestingly, participants in both conditions made around the same mark on the ruler — at about halfway. However, the difference in days was statistically significant: The one-year group would invest 289 days while the ten-year group would invest 583 days.

Sunk costs, in other words, guide people’s intuitions about relationships. “Together, both experiments confirmed the initial hypothesis that investments in terms of time, effort, and money make individuals more prone to stay and invest in a relationship in which they are unhappy,” the authors write. It’s a fascinating finding, and one that will need to be expanded on — especially since this is a hypothetical rather than truly empirical approach. Additionally, knowing people’s attachment styles — whether they crave or fear intimacy — will help detangle why everybody is so prone to staying in relationships that don’t nourish them. The good news is that you can get out: If Brad and Angelina taught us anything, it’s that a good divorce is better than a bad marriage.