Do you regret coming late for your best friend's birthday party or feel sorry at missing the late night movie show because of the massive traffic jam on the way? Do not worry much as you have a friend in rats!
Once thought to be uniquely and fundamentally human, researchers have found that even rats show regret.
Regret is the recognition that you made a mistake, that if you had done something else, you would have been better off.
"The difficult part of this study was separating regret from disappointment, which is when things aren't as good as you would have hoped," said A David Redish, a professor of neuroscience at University of Minnesota.
To measure the cognitive behaviour of regret in rodents, Redish and Adam Steiner, a graduate student in Neuroscience, developed a new task that asked rats how long they were willing to wait for certain foods.
In this task, named "Restaurant Row", the rats were presented with a series of food options but has limited time at each "restaurant".
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The findings showed that rats were willing to wait longer for certain flavours, implying they had individual preferences.
Sometimes, the rats skipped a good deal and found themselves facing a bad deal.
In humans, a part of the brain called the orbitofrontal cortex is active during regret.
"We found in rats that recognised they had made a mistake, indicators in the orbitofrontal cortex represented the missed opportunity," Redish said.
Interestingly, the rat's orbitofrontal cortex represented what the rat should have done, not the missed reward.
"This makes sense because you do not regret the thing you did not get, you regret the thing you did not do," he added.
By building upon this animal model of regret, Redish believes future research could help us understand how regret affects the decisions we make.
The research was published in the journal Nature Neuroscience.