Humans are always surprised to find that other living creatures aren't that different from us. Now comes word from researchers at the University of Minnesota have found that rats can feel regret -- just like us!
In their experiment -- its findings were published in Nature Neuroscience this week -- researchers learned that rats who made a bad choice registered regret in the same part of the brain where humans are believed to show regret: The orbitofrontal cortex. And the rats also do something very human-like, looking back at their missed opportunity, as if to say "I wish I could go back and do it all over again." Or maybe: "Regrets, I've had a few."
"What we found is that when a rat makes a mistake of its own agency, then the rat is able to recognize that mistake, and it thinks about the thing it should have done," said A. David Redish, a neuroscience professor at the University of Minnesota.
The rats in the study were given an opportunity to feed from four different flavored foods: banana, cherry, chocolate or unflavored. The foods were offered at different stations, or -- "restaurants" -- on a circular course created by researchers.
Each rat had preferences for different flavors and how much time they were willing to wait for food. The rats were taught that when they arrived at a restaurant, a tone would let them know exactly how long they had to wait for their food. Depending on the pitch of the tone, their wait could be anywhere from one to 45 seconds.
"What's happening is that they're coming and saying, 'Oh, it's 30 seconds, forget it,'" said Redish. "They make their decision to stay or go very quickly; either they stick around for the whole delay or they leave in two-to-three seconds. They open the door, see the long line and they say forget it."
Throughout their hour-long feeding session, the rats went around the course choosing to either stay and eat at different stations, or move on because the wait was too long.
As with humans, the feeling of regret frequently changed future behavior in rats.
So if, for example, a rat skipped a good food option (good flavor, short wait time) and encountered a worse food option afterwards (bad flavor with a long wait time), the rat might look back at the option it should have taken.
It might also do what many humans do, thinking about the station where it should have stayed and eaten: Researchers were able to see brain activity that indicates the rats were engaged in "mental time travel" -- imagining the alternate reality of eating in the restaurant that it skipped.
Using special technology – an invasive procedure that isn't easily performed on humans — researchers could see rats thinking about the restaurant they skipped through their brain activity.
And like humans, rats were also more likely to take a bad deal if they skipped a good one. They also quickly move on to the next feeding opportunity, after swallowing (literally) their bad choice.
"So it's very much: okay, fine, I'm going to eat this food then I'm moving on," Redish said.
When rats make a good decision, he said, they tend to stop, rest and groom themselves.
A good decision followed by a bad one might provoke what the researchers believe is consistent with feeling disappointment, which can be described as reality not living up to expectations through no fault of your own.
If they took a good deal and encountered a bad deal, the rats "don’t look back, they don't represent the previous restaurant. They represented the next restaurant" in their brain activity, Redish said.
The fascinating results don't just give us a glimpse into what goes on in the minds of rats, but they also give us insights into how our own brains work.
Researchers can look in great detail at the mechanism of a rat's brain and might eventually be able to do the same with humans.
If scientists can find a way to quantitatively measure emotions like regret in humans, they may eventually be able to figure out what happens in human brains when the brain mechanisms that produce emotions fail.
"A lot of psychiatry, a lot of clinical work, we need to think about it from an engineer's point of view," Redish said. "If we have a decision making machinery that's not working right, we need to understand that decision making machinery to figure out how to fix it."