Rats regret after making wrong choices, a new study shows.

Regretting over a lost opportunity was previously believed to be a trait exclusive to humans. University of Minnesota researchers have now found that rats regret too.

"Regret is the recognition that you made a mistake, that if you had done something else, you would be better off," said David Redish, Ph.D., a professor of neuroscience in the University of Minnesota Department of Neuroscience, in a news release. "The difficult part of this study was separating regret from disappointment, which is when things aren't as good as you would have hoped. The key to distinguishing between the two was letting the rats choose what to do."

The study doesn't just show that rats are able to feel a complex emotion such as regret, but also helps scientists understand decision-making skills in humans.

For the study, researchers put four rats under a test called "Restaurant Row." Rats were presented with food items at a "restaurant," but were given few seconds to make a choice, meaning that rats often chose a bad food over a good one. The rats were fitted with electrodes that helped researchers monitor the brain activity in the animals.

A brain region called orbitofrontal cortex is involved in decision making in humans. This part makes people 'feel' different pleasant and unpleasant emotions.  

"In humans, a part of the brain called the orbitofrontal cortex is active during regret. We found in rats that recognized they had made a mistake, indicators in the orbitofrontal cortex represented the missed opportunity. Interestingly, the rat's orbitofrontal cortex represented what the rat should have done, not the missed reward. This makes sense because you don't regret the thing you didn't get, you regret the thing you didn't do," said Redish.

Previous research has shown that people with damaged orbitofrontal cortex don't show any regret, National Geographic reported.

In future, researchers plan on studying how regret shapes decision-making in humans.

The study is published in the journal Nature Neuroscience.