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Nonhuman animals can engage in forms of metacognitive control and monitoring processes. However, very little testing of the relation between fluency and metacognition has been done in animals, and little research has assessed memory performance in relation to animals making immediate versus delayed judgments of their memory. Here, wagers made by monkeys during test trials served as a form of confidence measure of how well they could complete a memory test. These wagers occurred either after the delay interval between the sample presentation and the test (delayed judgments) or after the sample presentation but before the delay interval and the test (immediate judgments). Overall, no significant difference in performance was found between these two conditions. We also manipulated the fluency of stimuli by either contrasting small (low fluency) or large (high fluency) stimuli or by manipulating size and the degree to which stimuli were of similar perceptual classes (low fluency, harder to distinguish stimuli such as triangular shapes) or were dissimilar in color and shape (high fluency, clip art images). Although low fluency stimuli were remembered at lower levels, the monkeys showed no evidence of adjusting wagering behavior as a function of stimulus type. Thus, the present experiment showed no evidence that monkeys benefitted from delay of judgments of memory and no evidence of stimulus fluency affecting their confidence as measured by their wagering. Rather, most monkeys preferred consistent wagers across all trial types. This may indicate a metacognitive limitation or some other form of behavioral satisficing that led to suboptimal performance. 

Cognitive offloading occurs when an individual modifies a current decision scenario in a way that reduces the cognitive load or difficulty of a task. Children begin to engage in such offloading even before formal schooling begins. Using a manual rotation paradigm, preschool and elementary school children (3- to 9-years-old) were given perceptual discrimination tasks in which they had to compare two visual stimuli (either vertical and horizontal lines that intersected and they had to determine which was longer, or rectangular shapes or clip art animals that they had to compare to determine if the stimuli were the same or different). On some trials, offloading to the environment via rotation of one stimulus was beneficial to make the discrimination easier from the perspective of those stimuli aligning. Children in all age groups showed rotation of the various stimuli to make the task easier, although there was a developmental trend such that likelihood of accuracy and rotation increased with age. Additionally, children were more likely to rotate objects on difficult trials than easier ones and this often resulted in increases in accuracy. This tendency to rotate for the more difficult trials was associated with age. These results confirm that children can manipulate stimuli in ways that make comparing those stimuli easier, reflecting a form of (meta)cognitive offloading using the external environment to resolve internal uncertainty. 

Comparative research assessing metacognition in nonhuman animals contributes to the question of what form introspection could take in humans, non-humans, and other possibly conscious systems. We briefly review some major findings in comparative metacognition research, including some discoveries in areas looking at self-regulation and self-control. We discuss what data exist to address the three conditions for introspection defined by Kammerer and Frankish (this issue) in their target article. We suggest that two of three conditions are met by existing data from non-human primates, and that the third condition may be more difficult, but perhaps not impossible, to assess. We argue that a comparative and developmental approach to this question of how to define and measure introspection is a productive avenue to make progress in this area. 

Non-human primates evaluate choices based on quantitative information and subjective valuation of options. Non-human primates can learn to value tokens as placeholders for primary rewards (such as food). With those tokens established as a potential form of ‘currency’, it is then possible to examine how they respond to opportunities to earn and use tokens in ways such as accumulating tokens or exchanging tokens with each other or with human experimenters to gain primary rewards. Sometimes, individuals make efficient and beneficial choices to obtain tokens and then exchange them at the right moments to gain optimal reward. Sometimes, they even accumulate such rewards through extended delay of gratification, or through other exchange-based interactions. Thus, non-human primates are capable of associating value to arbitrary tokens that may function as currency-like stimuli, but there also are strong limitations on how non-human primates can integrate such tokens into choice situations or use such tokens to fully ‘symbolize’ economic decision-making. These limitations are important to acknowledge when considering the evolutionary emergence of currency use in our species. This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates’.