Multiple demonstrations of metacognition in nonhumans: Converging evidence or multiple mechanisms?

Metacognition allows one to monitor and adaptively control cognitive processes. Reports from the last 15 years show that when given the opportunity, nonhuman animals selectively avoid taking difficult tests of memory or perception, collect more information if needed before taking tests, or "gamble" more food reward on correct than on incorrect responses in tests of memory and perception. I review representative examples from this literature, considering the sufficiency of four classes of mechanism to account for the metacognitive performance observed. This analysis suggests that many of the demonstrations of metacognition in nonhumans can be explained in terms of associative learning or other mechanisms that do not require invoking introspection or access to private mental states. Consideration of these accounts may prompt greater appreciation of the diversity of metacognitive phenomena and may inform theoretical positions about the nature of the mental representations underlying metacognition.