When the researchers compared the scans of participants, they found that those who most often correctly chose the pot with the most money had more activation in the amygdala, while those who made suboptimal decisions had more activation in the anterior insula. “The amygdala encodes the actual money, the sum,” says Vestergaard. In their study, the authors concluded that the amygdala is responsible for processing information about the overall experience, not just whether or not it ends well. And that’s important, because that’s the thing you should be paying attention to if you want to optimize winning money.
In contrast, they wrote, the anterior insula “marks down,” or penalizes, sequences in which the coins’ sizes start to decrease over time. But rationally, temporary decreases are something you should ignore, not focus on. After all, a decrease at the end of an experience may be offset by increases at the beginning.
“The statistical strength of this neural code can separate efficient decision-makers from suboptimal decision-makers,” the authors wrote in their study. “Optimal decision-makers encode overall value more strongly, and suboptimal decision-makers encode the disincentive markdown more strongly.”
Vestergaard acknowledges there are limitations to this study. The subjects were all men ages 21 to 36. Could there be a difference between men and women, or between old and young people? What about differences between, say, artists or mathematicians, who might have different ideas about what makes them happy or about what’s valuable? “These are all good questions,” Vestergaard says. “This has to be next time, I’m afraid.”
Nathaniel Daw, a professor of computational and theoretical neuroscience at Princeton who was not involved in this study, says that while the happy ending effect has been known for a while, scientists still don’t know why people will consistently opt for bad or irrational choices. “We don’t understand very well why they arise—what is the mechanism for how the brain evaluates options from experience, and why does it make these apparent mistakes?” he wrote in an email to WIRED. “The brain measurements provide additional information that can give us clues about that.”
One theory was that we may just be forgetting the good parts of the experience because they happened earlier. But this research shows that this isn’t the result of poor memory, Daw argues: “The fact that they find a distinct brain signal assessing how rewards are declining, separate from signals related to how good the options are, supports the idea that the brain is actively constructing this evaluation.”
Daw added that in other studies the anterior insula is often associated with processing negative experiences, disgust, and pain. “It really seems like people are actively repulsed by the declining options, which is not necessarily what I would have expected,” he wrote.
Vestergaard isn’t ready to speculate on what it means that the anterior insula is activated. What is important, he says, is that even though a negative or declining trend may not be relevant information, the brain is penalizing the experience because of it. “Your brain registers it, and it informs your decisions, whether you want it or not,” says Vestergaard.
There may be some reasons why an animal’s brain wants to keep track of upward or downward trends. Daw notes that it can be an important adaptation for foraging animals that need to keep track of whether a food source is getting more or less available. If an animal can make a quick decision about whether to continue looking for food in one place, or whether to change course because their options are dwindling, it could find food more efficiently.
When it comes to the way people respond to scarce resources, we might even try to game our own neurobiology. As far back as 1993, the behavioral economists George Loewenstein and Drazen Prelec published a paper in Psychological Review suggesting that people prefer an improving trend or sequence of experiences, rather than a decreasing trend, because they like reveling in the anticipation of a positive event. “Individuals are not helpless in the face of their urges,” Loewentstein and Prelec wrote. They pointed to real-life examples like participating in dieting clubs or the Social Security system, activities in which people put off the enjoyment of something now so that they can indulge in it later, whether it be dessert or the comfort of a healthy retirement savings.