National Geographic News
Photo of a lab rat.

Researchers at the University of Minnesota implanted electrodes in the brains of four rats and trained them to run a maze.

  Photograph by Bill Gallery, Doctor Stock/Science Faction/Corbis

Jane J. Lee

National Geographic

Published June 8, 2014

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. (See "Hand Washing Wipes Away Regrets?")

If you really want to study emotions or feelings like regret, says Redish, you can't just ask people how they feel. So when psychologists and economists study regret, they look for behavioral and neural manifestations of it. Using rats is one way to get down into the feeling's neural mechanics.

Redish and colleague Adam Steiner, also 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.

Making Choices

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.

The maze consisted of a circle with four spokes radiating out from its circumference. At the end of three spokes was food flavored with banana, cherry, or chocolate. At the end of the fourth spoke was unflavored food. When a rat arrived at a spoke, a tone would sound before it received the food. The tone's pitch indicated how long the rat would have to wait before getting the treat; it could be anywhere from one to 45 seconds.

The rat then had to make a choice. It could either wait the allotted time before getting the food, or it could move on to the next spoke. The rats were allowed to run the maze for only an hour, so their "foraging" needed to be as efficient as possible.

Bad Choices

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.

Looking Forward

Rats that met with disappointment reacted very differently. Some would sit and look at the choice in front of them. Others would visualize their next choice. These rats, says Redish, were looking toward the future.

Matt Roesch, a neuroscientist at the University of Maryland in College Park who was not involved in the study, was intrigued by the experiment. Finding a human emotion like regret in an animal, he says, and being able to see it manifested in brain activity is exciting.

"If you have a strong feeling of regret, you should be able to use that information to guide future decisions, to make better ones," Roesch says. Yet people who have psychiatric diseases like schizophrenia can't do this. Alcoholics and drug addicts also seem unable to make better decisions based on their regret. (See "NIDA's Director Tells Us What We Know—and Need to Know—About Marijuana.")

Roesch, who studies the neural basis of addiction, says he would love to see a future study on whether addiction in rats changed the results of the experiment.

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

Follow Jane J. Lee on Twitter.

22 comments
Michael Pretorius
Michael Pretorius

If this line of indirect study, into human behaviour, via mammal behaviour in general, is a mature scientific endeavour I suppose there should be NEW behaviour altering knowledge already in practice that hopefully; consistently / actually / empirically improves human existence in a better way than was already available to human societies for the past how many thousands of years. Science as a conscious endeavour can change the physical world, but the world of thoughts, abstractions and meaning seems to be, by definition out side the scope of the materialistic world view. That is, if I have missed the viable materialistic explanation of consciousness.

The beauty of anthropomorphism is such a useful behavioural tool:

"The universe seems neither benign nor hostile, merely indifferent."

Carl Sagan

susanne heinitz
susanne heinitz

This is a very interesting article...and one step forward towards 'animals are not objects'!

Peggy Lewis
Peggy Lewis

I think this is what the aliens are doing to humans when they abduct them and do experiments..  (aka, "earthlings regret choosing cake over salad")  soo important to know..

Julianna Bragg
Julianna Bragg

I knew someone would turn this into a political debate...geez.....I'm sure a rat would prefer a cheese thing over a broccoli , although they will eat anything... p.s. I am wondering if these tests were conducted with the old reward or punishment thing...not exactly real regret...although the brain think I really don't know.....I also know a few rats in my life who have never felt or shown ANY regret! lol....

Nick Keranen
Nick Keranen

I never really thought that a rat would actually need to think about whether or not they wanted to eat a piece of food. I thought they just ate the thing that was closest to their reach. I also didn't know that a rat would have flavor preferences. That they actually do this is cool.

Diane Murphy
Diane Murphy

I do not agree with cruelty to animals of any kind.  However, human experiments carried out on animals have been the source of which untold human lives have been changed for the better. Many cures and medications tried out on animals first have led to the eradication or treatment of symptoms of harmful disease causing organisms -aids, blindness, mental illness,  measles, mumps, polio, etc.

J. Griffin
J. Griffin

All animals are conscious beings. A lot of people forget too easily that humans are animals. So that basically means that all human emotion is in fact animal emotion. 

Alex Afu
Alex Afu

No more experiments!!!
The rats said to me: I am someone NOT ¨SOMETHING¨.



Do not go where the path may lead, go instead where there is no path and leave a trail.

Manuel Dias
Manuel Dias

National Geographic mis-printed the title for this article.


Instead of Rats it should have been Liberals

Eric Vinyard
Eric Vinyard

In a further study, rats were given access to alcohol and Facebook, and upon awaking the next day, immediately began sending apologies for the emotional, borderline-creepy messages they had inboxed the night before to random users they barely knew.

Dana Pope
Dana Pope

thanks for helping me learn what i did not learn at home or in school - how to define your feelings by actions !

Sabine Kindschuh
Sabine Kindschuh

Seems to me that the scientists involved in this do not regret putting animals through such totally superfluous studies. I find this appalling.

Vonne Pitcher
Vonne Pitcher

Don't like to read about experiments on animals (ie putting electrodes in their brains) and there doesn't even seem to be a reason for this pointless exercise.

bill greig
bill greig

@Nick Keranen They'll also come find you if they escape from their cage and can't get back in.  Had a couple of pet rats in my bedroom once, used to wake up with them nosing around my head, having traveled all the way across the room.

bill greig
bill greig

@Manuel Dias You're right.  I STILL regret starting as  a conservative all those years ago.

KENNETH LANE
KENNETH LANE

@Manuel Dias Wrong, a study involving Rightwing subjects would not yield  any resulting regret mechanisms hence the Liberal rat study.

Julianna Bragg
Julianna Bragg

@Eric Vinyard  Ha Ha, spot on...thanks for the words and laugh....ps I know some rats that never express any regret! lol~

D. Jensen
D. Jensen

@Dana Pope The implications here are huge.  One would have to be rather obtuse to not understand this

bill greig
bill greig

@Sabine Kindschuh It seems to be in the nature of inquisitive beasts like ourselves to torment weaker animals to learn things.  Look at chimps, or cats.  Also, many things in the world are much more cruel to rats than man.  Arguably, at least these were warm and safe and well-fed, and possibly even pet and groomed by bored lab assistants, up until the experiment.

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