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The strongest cross-species comparison concerns a function: using information about the reliability of one's cognition to regulate behaviour. Metacognitive monitoring can influence whether an individual answers, seeks more information or declines a test. Humans can additionally give verbal explanations, but a verbal report is neither necessary for adaptive uncertainty control nor sufficient proof of an accurate account of its mechanism.

Robert R. Hampton tested two rhesus macaques with images on a monitor. After viewing a sample and waiting through a delay, the monkeys sometimes chose whether to accept a memory test before seeing its alternatives. Correct tests yielded a preferred reward, errors none, and declining a smaller guaranteed reward. Accepted tests were more accurate than forced tests, and declining increased when memory was experimentally weakened. The two animals did not meet every condition equally clearly.^[ref] Separating the acceptance decision from the test display reduces explanations based solely on the visible test alternatives. It does not make the animal's subjective experience directly observable.

A complementary demonstration used auditory-duration discrimination in rats, with an option to decline difficult tests. A noise lasted between two and eight seconds; illuminated nose-poke apertures signalled whether a test could be accepted or declined, and two levers then represented the duration categories. A correct test earned six food pellets, an error none, and declining three.^[ref] The opportunity to avoid an error is an operational measure of uncertainty regulation, but interpreting the same behaviour requires comparing metacognitive and simpler learning models. A stimulus near the trained category boundary can acquire a low response value, making an uncertainty option attractive without an explicit representation of knowing.

The optimal confidence threshold for an uncertainty response clarifies a further issue. If correct testing earns $r$, an error earns zero and declining earns $s$, an individual maximizing the expected value of reward should accept when $pr>s$, where $p$ is its estimated probability of being correct. Identical beliefs can therefore produce different opt-out behaviour when reward size, risk preference or opportunity cost differs. Species comparisons must match or model these contingencies, as well as motivation, sensory ability and task experience.

More diagnostic tests use novel stimuli or task transfer, omitted study samples, memory manipulations not fully predictable from external cues, and conditions that separate delay, retrieval strength and reinforcement history. Different candidate models should predict held-out behaviour. Information seeking when uncertainty cannot be resolved by repeating a familiar action is especially useful. No single control eliminates all first-order alternatives; converging tests constrain them progressively.

Human advantages plausibly include language-supported explanation, explicit general beliefs about one's abilities, instruction-driven strategies and social communication of confidence. These are hypotheses about particular components, not a licence to infer a categorical absence of uncertainty monitoring in every nonhuman species. Human verbal judgments also use learned cues and can be miscalibrated. Current experiments support specific functional parallels in monitoring and control, while the equivalence of reflective awareness, domain generality and subjective experience remains a separate question.