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Surprising Discovery: Important Human Emotion Found in Unlikely Species

January 06, 2015

Story at-a-glance

  • Recent research suggests that rats, like humans, show regret when they make bad choices
  • The study involved a task called “Restaurant Row” that presented rats with dining decisions – decisions that were influenced by the rats’ food preferences and their ability to be patient
  • Researchers discovered that when the rats made bad decisions, they showed regret both behaviorally and neurologically
  • The rats also altered their behavior after making a bad choice. For example, they ate the results of their bad choices very quickly instead of savoring them, and they exercised greater patience waiting to eat at the next “restaurant”

By Dr. Becker

It seems another “exclusively human” ability isn’t so exclusive after all. Scientists have recently discovered that rats possess the ability to show regret. Displays or feelings of regret are the result of a cognitive (reasoning) process. When experts in various fields study regret, they look for behavioral and neurological expressions of it.

Researchers at the University of Minnesota’s Department of Neuroscience set out to measure the cognitive behavior of regret in rats, using established definitions of the word. According to A. David Redish, Ph.D., professor of neuroscience at U of M:

“Regret is the recognition that you made a mistake, that if you had done something else, you would have been better off.”

Redish goes on to explain that the biggest challenge of the study was separating regret from disappointment, which is the feeling we experience when things don’t turn out as we hoped. “The key to distinguishing between the two was letting the rats choose what to do,” said Redish.

Rats Make Dining Choices on ‘Restaurant Row’

Redish and Adam Steiner, a graduate student, created a task for rats called “Restaurant Row.” The task required the rats to decide how long they were willing to wait for certain kinds of food. Redish compared the task to waiting in line at a restaurant. If the line at the Chinese restaurant is too long, you may opt to eat at the Italian place down the street instead.

“Restaurant Row” was actually a circular apparatus with four spokes sticking out from it. At the end of three of the spokes the researchers placed food flavored with banana, cherry, or chocolate. The fourth spoke contained unflavored food.

When a rat arrived at a spoke, a tone would sound before the food was accessible. The pitch of the tone told the rat how long he’d have to wait – anywhere between 1 and 45 seconds -- before the food would become accessible.

The rats were faced with a choice – they could either wait an unknown amount of time before getting the treat, or they could move on to the next “restaurant” (spoke) hoping for a shorter wait in line. The rats were given only an hour to restaurant-hop, so the better their choices, the more they got to eat.

Rats Regret Their Bad Choices

The researchers learned each rat had his own preference for food flavors, and also his own level of patience. Both of these inclinations created specific nerve-cell patterns in the rat’s brain that allowed Redish and Steiner to know when a particular rat was thinking about a particular flavor of food.

When a rat made a choice not to wait at one spoke and moved on to the next, only to discover he’d have to wait even longer for food at his second stop, two things occurred. The rat would look back to the first spoke, and the specific nerve-cell brain pattern associated with that first choice would “light up.”

According to Redish, the two-phase sequence was the rat displaying regret. Not only did the little guy physically look backward to the first spoke, he was also thinking about the choice he didn’t make. In addition, the scientists discovered that just like people, the rats were more apt to wait longer than normal at the next spoke after making a bad decision.

Interestingly, the rats would also eat the food that resulted from a bad choice in about 5 seconds flat, whereas their normal behavior was to spend about 20 seconds grooming themselves and eating. This also sounds very human-like to me. How many of us have given in to a craving for food we know we shouldn’t eat, and then shoved it down our throat, hardly noticing the taste?

Do Rats Learn to Avoid Regret?

Members of the scientific community are intrigued by the results of the University of Minnesota study, which was published last year in the journal Nature Neuroscience.1

Matt Roesch, a neuroscientist at the University of Maryland, told National Geographic, “Finding a human emotion like regret in an animal, and being able to see it manifested in brain activity is exciting.”2

In theory, strong feelings of regret should prompt us to use that information to make better decisions in the future. This seems to be the case with some people, but not others – especially those with psychiatric illnesses and addictions.

Redish hopes in the future to be able to translate what he's seen in his rats to human behavior. "Humans avoid regret," says Redish. "Do rats?"

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Sources and References

  • 1 Nature Neuroscience 17, 995–1002 (2014) doi:10.1038/nn.3740
  • 2 National Geographic, June 2014
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