Interesting Animal - The Rat

According to a study carried out at the University of Minnesota, in the USA, rats experience regret when their actions make them miss out on better food options.

(Scientists believe that the emotion of "regret" is unique to humans, and is different to disappointment.  Prof David Redish said, "Regret is the recognition that you made a mistake, that if you had done something else, you would have been better off. The hard part was that we had to separate disappointment, which is just when things aren't as good as you hoped. The key was letting the rats choose.

Funnily the dictionary defines regret as a feeling of sadness, repentance, or disappointment.)