While conducting research on decision-making in rats, the University of Minnesota's David Redish and his graduate student, Adam Steiner, made a different discovery. The pair saw that when a rat made a mistake, it stopped and looked backwards, as if it felt regret.
As Wired reports, the two decided to create an experiment that should cause rats to have regret, then measured the behavioral and neurophysiological markers that are consistent with the feeling. They taught rats to go into a contraption called "restaurant row" that had four different sections serving various flavors of pellets at different intervals (for example, a cherry-flavored pellet might come out in eight seconds, while a banana-flavored pellet could take 20 seconds).
Each rat had a threshold based on their taste preference, and Steiner and Redish used those thresholds to see what was a "good deal" and what was a "bad deal," and what happened when the rat passed over a good deal. The researchers found that when a rat skipped a good deal and went to a bad deal, they would stop and look at the restaurant they had bypassed. "It looked like Homer Simpson going, 'D'oh!'" Redish told Wired.
Redish doesn't think the findings should be too shocking. "We're not surprised by hearts or legs being similar, so why should we be surprised that brain structures and computations are similar?" he said. The results of the observation were published Sunday in Nature Neuroscience. Read an in-depth look at the study at Wired.