Rats can experience regret similar to the way humans do, according to a new study published in Nature Neuroscience.
Researchers gave rats various food options, putting longer wait times for the better food; rats that passed their favorite foods for poorer substitutes looked back at the previous room, Live Science reported.
"The rat is representing the counterfactual--the 'what might have been,'" said lead study author David Redish, a neuroscientist at the University of Minnesota in Minneapolis, as quoted by Live Science.
Redish and his research team set up a "Restaurant Row" for the rats, a circular enclosure with paths that led to rooms with different foods. Each rat explored the complex for one hour, during which it could only go in one direction.
When passing each pathway, the rat heard a tone designating how long the wait time for that particular food would be. The animals had to wait longer for their favorite foods.
Rats that decided not to wait for their favorite foods and found a worse option at the next restaurant glanced backward at the room they passed, Live Science reported. Additionally, the rats tended to eat their poor choice rapidly, similar to a human dealing with regret. They were also more prone to picking a "worse deal" in the future.
"Regret is something we think of as very human and very cognitive," said Redish, as quoted by Live Science, but "we're seeing that the rats are much more cognitive than we thought."
The researchers also scanned the rats' brains to "read their minds. They discovered that the animals were thinking of the restaurant they passed up, not the food that they missed, implying that they were ruminating over their actions and not just the missed treat.
"Regret is the recognition that you made a mistake, that if you had done something else, you would have been better off," said Redish, as quoted by BBC News.
"The hard part was that we had to separate disappointment, which is just when things aren't as good as you hoped. The key was letting the rats choose."
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