This study challenges the idea that non-primates are also capable of metacognition, "reasoning or thinking about one's own thinking".
"The study involved what is called a "duration-discrimination" test--offering rats rewards for classifying a signal as either short or long. As in most such tests, the "right" answer led to a large food reward, while a "wrong" answer led to no reward at all. The twist, however, is that before taking the duration test, the rats were given the chance to decline the test completely. If they made that choice, they got a small reward anyway.
"If rats have knowledge about whether they know or don't know the answer to the test, we would expect them to decline most frequently on difficult tests," said Crystal. "They would also show the lowest accuracy on difficult tests that they can't decline. Our data showed both to be true, suggesting the rats have knowledge of their own cognitive states.""
If animals really do have the ability to "know what they don't know", it makes me wonder how much of our projections about their psyches may be plausible (like in all those cartoons we grew up watching). I suddenly have a craving to watch The Secret of NIMH again.