David Redish and his grad student Adam Steiner of the University of Minnesota didn’t set out to study if rats experience regret.
They were looking at decision-making in rats. But something about the behavior of their subjects struck them as interesting. When a rat made a mistake, it stopped and looked backwards. Anthropomorphically, it looked to Steiner and Redish as if the rat was feeling regret.
That observation lead them to design an experiment to look at behavioral and neurophysiological markers consistent with regret in rats.
Read the whole story at Zoologic: Rats Regret Making the Wrong Decision.