Rats have regrets too, says study
Regret - that most corrosive of emotions - turns out to be common to men and rodents. Scientists have done an experiment using food treats to entice rats into a food station, where they could either wait for a meal or go to the next stop. The ones that decided to move on, and then had to wait even longer, showed signs of regretting their hasty decision to move to an even worse deal.
Source: PM | Duration: 4min 23sec
MARK COLVIN: "Of all sad words of mice and men, the saddest are these, it might have been."
Now we know it's not just a saying.
Regret, that most corrosive of emotions, turns out to be common to men and rodents.
Scientists have done an experiment using food treats to entice rats into a food station, where they could either wait for a meal or go to the next stop.
The ones that decided to move on, and then had to wait even longer, showed signs of regretting their hasty decision to move to an even worse deal.
It's the first time it's been shown that mammals other than humans experience regret.
Will Ockenden reports.
WILL OCKENDEN: During this long weekend, it's likely that some in the human species will have woken up after a particularly messy night with a serious case of the 'oh-nos.'
That feeling that at some point during the previous evening, you made a huge mistake.
DAVID REDISH: Regret is a recognition that you've made a mistake; it's an error in your agency
WILL OCKENDEN: David Redish is a professor in the Department of Neuroscience at the University of Minnesota.
DAVID REDISH: We were trying to understand how rats make decisions, because rats make decisions very much like humans do. Under certain conditions, rats looked like they were showing regret over mistakes they made.
WILL OCKENDEN: So a test was developed for the rats which would allow the researchers to separate the emotion of regret from disappointment.
DAVID REDISH: We designed a task where the rats actually made their own choices. So we were able to construct a situation in which we could see both when they made a mistake, and that's why things weren't as good, and when things just weren't as good. And we found differences both in the behaviour and in the neurophysiology when the rats were in regret inducing situations.
WILL OCKENDEN: They trained the rats to do a task called the 'restaurant row.' The rats would run around a square and at each corner, there was an exit which led to a food station.
Each food station gave a different flavoured meal. There was cherry, chocolate, banana, and plain.
When the rat entered the restaurant, a tone would play that would signify a duration before the meal would be served.
David Redish says it's a bit like entering a Chinese restaurant and seeing a long line.
DAVID REDISH: When you leave the first restaurant to go to the second one, you don't know how long the line's going to be at the second restaurant. So what happens if you essentially leave a pretty good line, you know, a short delay, and find yourself now facing a long delay? You could have done better by actually taking the better deal first, and that's your mistake. And so that's the key, is that the rats then recognised when they had missed that first deal, that good deal, and now faced a bad deal.
WILL OCKENDEN: And what does regret look like on a tiny, little rat's face?
DAVID REDISH: (Laughs) It's hard to tell on the face to be honest. But what they do is they'll stop and they'll look backwards, but your body stays forwards. It' looks like somebody going 'oh man! I messed up." And then after they do that, then they turn back forward, and they're actually much more likely to stick around for the bad deal after they've messed up on the good deal.
The real proof of the regret was in the neurophysiology, which was that when the animal came to that turn to look back, we actually saw that its orbital frontal cortex, which is the part of the brain that in humans is active during regret, that same part of the brain in rats represented what it should have done. It was the might have been, I could have done that.
WILL OCKENDEN: Often the human experience of regret is not the things you didn't get, but rather the things you didn't do.
This study goes some way in showing a rat's experience of regret is much the same.
DAVID REDISH: This means that we can start to ask these questions about what are the mechanisms of these decision making components that, you know, are similar. And of course, also what are different?
We know that the rats express regret. We know that they behave differently in these situations, and we know that it has consequences down the line. But we don't know whether they avoid regret.
So one of the things that humans do, of course, is we do a lot of things, sometimes very silly things, to avoid the possibility of regret. We don't know whether rats can avoid regret or not, it's a very interesting question.
MARK COLVIN: David Redish, from the University of Minnesota, ending Will Ockenden's report.
That study published today in Nature Neuroscience.