Rats' knowledge of incorrect responses in a matching-to-sample task.

The idea that rats possess some knowledge about having been incorrect when having previously made an incorrect response is proposed. A matching-to-sample task with a second choice was used to assess the hypothesis. Only if the correct lever was chosen on the second choice was the animal rewarded. Further, the second choice was offered whether the animal was initially correct or incorrect in its first choice, preventing it from "knowing" if it had been correct in its initial decision. If rats possessed some knowledge whether they had been correct or not, then the number of correct second choice responses after an incorrect first one should have been greater than chance. The current experiment provided some evidence that the rats did "know" when its choices were incorrect.