Putative metacognition data in animals may be explained by non-metacognition models (e.g., stimulus generalization; Smith et al., 2008). The objective of the present study was to develop a new method for testing metacognition in animals that cannot be explained by non-metacognition models. Animals are sometimes in a high or low state of performance. Metacognition is the hypothesis that animals know that they are in a high or low state. On a difficult problem we assume that animals choose to repeat a stimulus if they are in a low state of performance. Rats were first presented with a brief noise duration which they would subsequently classify as short or long. Rats were sometimes forced to take an immediate duration test, forced to repeat the same duration, or had the choice to take the test or repeat the duration. Metacognition, but not alternative non-metacognition models, predicts that accuracy on difficult durations is higher when subjects are forced to repeat the stimulus compared to trials in which the subject chose to repeat the stimulus, a pattern observed in our data. Simulation of a non-metacognition model supports the conclusion that our data document metacognition in rats.