Researchers studied brain areas involved in decision making, evaluating outcomes.
Could've, should've, would've. Everyone has made the wrong choice at some point in life and suffered regret because of it. Now a new study shows we're not alone in our reaction to incorrect decisions. Rats too can feel regret.
Regret is thinking about what you should have done, says David Redish, a neuroscientist at the University of Minnesota in Minneapolis. It differs from disappointment, which you feel when you don't get what you expected. And it affects how you make decisions in the future.
Redish and colleague Adam Steiner at the University of Minneapolis, found that rats expressed regret through both their behavior and their neural activity. Those signals, researchers report today in the journal Nature Neuroscience, were specific to situations the researchers set up to induce regret, which led to specific neural patterns in the brain and in behavior.
When Redish and Steiner looked for neural activity, they focused on two areas known in people—and in some animals—to be involved in decision-making and the evaluation of expected outcomes: the orbitofrontal cortex and the ventral striatum. Brain scans have revealed that people with a damaged orbitofrontal cortex, for instance, don't express regret. To record nerve-cell activity, the researchers implanted electrodes in the brains of four rats—a typical sample size in this kind of experiment—then trained them to run a "choice" maze.
Each rat had its own preferences regarding flavor and patience. And those preferences manifested in specific nerve-cell patterns in its brain. Redish and Steiner could thus tell when a particular rat was thinking about, say, the chocolate-flavored versus the cherry-flavored food. When a rat passed up food at one spoke and moved on to the next, then realized it would have to wait even longer for food at the second spoke, two things happened: It would look back to the previous spoke, and the specific nerve-cell pattern in its brain that represented that first choice would light up.
"That's the regret," says Redish. Not only were the rats physically looking backward; they were also thinking about the choice they hadn't made. What's more, "just like humans," says Redish, the rats were more likely to take a "bad deal"—or wait longer than they normally would for their next piece of food—after a regretful decision. The rats would also hastily consume food that stemmed from a bad choice, spending only about five seconds with the treat. Normally the rats would spend about 20 seconds grooming themselves and eating their food.