Researchers led by Amitai Shenhav at Princeton University have found that people who choose between two or more positive outcomes display paradoxical feelings of pleasure and anxiety.
In one experiment, 42 people rated the desirability of more than 300 products using an auction-like procedure. Then they looked at images of paired products with different or similar values and were asked to choose between them. Their brain activity was scanned using functional magnetic resonance imaging (fMRI). After the scan, participants reported their feelings before and during each choice. They received one of their choices at the end of the study.
Choices between two highly valued items (high-high), such as a digital camera and a camcorder, were associated with the most positive feelings and the greatest anxiety, compared with choices between items of low value (low-low), like a desk lamp and a water bottle, or between items of different values (low-high). Functional MRI scans showed activity in two regions of the brain, the striatum and the prefrontal cortex, both known to be involved in decision-making. Interestingly, lower parts of both regions were more active when subjects felt excited about being offered the choice, while activity in upper parts was strongly tied to feelings of anxiety.
This evidence that parallel brain circuits are associated with opposing emotional reactions helps to answer a puzzling question, according to Shenhav: "Why isn't our positivity quelled by our anxiety, or our anxiety quelled by the fact that we're getting this really good thing at the end? This suggests that it's because these circuits evolved for two different reasons," he said. "One of them is about evaluating the thing we're going to get, and the other is about guiding our actions and working out how difficult the choice will be."
The study, "Neural correlates of dueling affective reactions to win-win choices," was published July 14 in the Proceedings of the National Academy of Sciences
. Shenhav conducted the research as a graduate student at Harvard University, along with Professor of Psychology and Neuroscience Randy Buckner, the study's senior author.
A second fMRI experiment showed that the same patterns of emotional reactions and brain activity persisted even when the participants were told before each choice how similarly they had valued the items. Their anxiety didn't abate, despite knowing how little they stood to lose by making a "wrong" choice. In a third experiment, Shenhav and Buckner tested whether giving people more than two choices increased their levels of anxiety. Indeed, they found that providing six options led to higher levels of anxiety than two options, particularly when all six of the options were highly valued items. But positive feelings about being presented with the choice were similar for two or six options.