An anonymous reader writes: Researchers at the University of Minnesota have discovered that rats in a decision making experiment showed three behaviors consistent with regret. David Redish and his graduate student Adam Steiner '...trained rats to do a task they call “restaurant row.” The rat ran around a circle past a series of four spokes, each leading to a different flavor of food. As the rat came to the entrance of each spoke, a tone sounded that indicated how long it would have to wait to receive that specific flavor of food. The rat could choose whether to stay or go, depending on how much it liked that food and how long it would have to wait...The rats showed three behaviors consistent with regret. First, the rats only looked backwards in the regret conditions, and not in the disappointment conditions. Second, they were more likely to take a bad deal if they had just passed up a good deal. And third, instead of taking their time eating and then grooming themselves afterwards, the rats in the regret conditions wolfed down the food and immediately took off to the next restaurant.'