Information seeking by rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella)

Metacognition in wild Japanese macaques: cost and stakes influencing information-seeking behavior

Metacognition allows us to evaluate memories and knowledge, thus enabling us to distinguish between what we know and what we do not. Studies have shown that species other than humans may possess similar abilities. However, the number of species tested was limited. Testing ten free-ranging Japanese macaques (Macaca fuscata) on a task in which they had to find food hidden inside one of the four opaque tubes, we investigated whether these subjects would seek information when needed. The monkeys could look inside the tubes before selecting one. We varied three parameters: the baiting process, the cost that monkeys had to pay to look inside the tubes, and the reward at stake. We assessed whether and how these parameters would affect the monkeys' tendency to look inside the tube before selecting one. When they were not shown which tube contained the reward, nine monkeys looked significantly more frequently in at least one condition. Half of them tended to reduce their looks when the cost was high, but only when they already knew the location of the reward. When a high-quality reward was at stake, four monkeys tended to look more inside the tubes, even though they already knew the reward's location. Our results are consistent with those of rhesus macaques, suggesting that metacognitive-like abilities may be shared by Cercopithecidae, and that, at least some monkeys may be aware of their lack of knowledge.

Rats did not show evidence of prospective information-seeking: a pilot study

Information-seeking behavior often features in research on metacognition in non-human animals; some species seek more information when they do not know the location of a food reward. Rats are known to do this in situations of uncertainty, but it is still unclear if they seek information prospectively for solving a later problem. In this study, we investigated rats' information-seeking responses in two areas that presented different cognitive challenges (N = 4). In one area, a memory task was presented in which rats could access a cue for a food reward during the information-seeking phase of a trial, but the cue was removed before the subsequent test phase. In the other area, a discrimination task presented a cue that was available in both the information-seeking and the test phases, so that it was not necessary to seek information prospectively. The memory and discrimination test trials were given in quasi-random order (Experiment 1). Rats explored in the memory task area no more than in the discrimination task area during the information-seeking phase, even after extensive training. When they were exposed exclusively to the memory task over multiple sessions (Experiment 2), they developed a strategy of exploring the available object cues. In Experiment 3, rats were found to stay longer in an area, which had an object than in other, less potentially informative areas; they were sensitive to the presence of information. Although these results did not support the existence of prospective information-seeking in rats, they do not necessarily imply that rats lack related abilities. This consideration is due to the constraints of the small sample size and the limited scope of the testing environment. Accumulating not only positive but also negative evidence would further understanding of the factors influencing metacognitive responses in non-human animals.

Great apes and human children rationally monitor their decisions

Several species can detect when they are uncertain about what decision to make-revealed by opting out of the choice, or by seeking more information before deciding. However, we do not know whether any nonhuman animals recognize when they need more information to make a decision because new evidence contradicts an already-formed belief. Here, we explore this ability in great apes and human children. First, we show that after great apes saw new evidence contradicting their belief about which of two rewards was greater, they stopped to recheck the evidence for their belief before deciding. This indicates the ability to keep track of the reasons for their decisions, or 'rational monitoring' of the decision-making process. Children did the same at 5 years of age, but not at 3 years. In a second study, participants formed a belief about a reward's location, but then a social partner contradicted them, by picking the opposite location. This time even 3-year-old children rechecked the evidence, while apes ignored the disagreement. While apes were sensitive only to the conflict in physical evidence, the youngest children were more sensitive to peer disagreement than conflicting physical evidence.

An evolutionary view of self-awareness

The capacity to be self-aware is regarded as a fundamental difference between humans and other species. However, growing evidence challenges this notion, indicating that many animals show complex signs and behaviors that are consonant with self-awareness. In this review, we suggest that many animals are indeed self-aware, but that the complexity of this process differs among species. We discuss this topic by addressing several different questions regarding self-awareness: what is self-awareness, how has self-awareness been studied experimentally, which species may be self-aware, what are its potential adaptive advantages. We conclude by proposing alternative models for the emergence of self-awareness in relation to species evolutionary paths, indicating future research questions to advance this field further.

A Dissociative Framework for Understanding Same-Different Conceptualization

Cognitive, comparative, and developmental psychologists have long been interested in humans' and animals' ability to respond to abstract relations. Cross-species research has used relational matching-to-sample (RMTS) tasks in which participants try to find stimulus pairs that "match" because they express the same abstract relation (same or different). Researchers seek to understand the cognitive processes that underlie successful matching, and the cognitive constraints that create species differences in these tasks. Here we describe a dissociative framework drawn from cognitive neuroscience. It has strong potential to illuminate the area of same-different conceptualization. It has already influenced comparative research on categorization and metacognition. This dissociative framework also shows that species differences in same-different conceptualization have resonance with species differences in other comparative domains.

Rhesus monkeys (Macaca mulatta) monitor evolving decisions to control adaptive information seeking

Adaptive decision making in humans depends on feedback between monitoring, which assesses mental states, and control, by which cognitive processes are modified. We investigated the extent to which monitoring and control interact iteratively in monkeys. Monkeys classified images as birds, fish, flowers, or people. At the beginning of each trial, to-be-classified images were not visible. Monkeys touched the image area to incrementally brighten the image, referred to as the brighten response. The amount by which brightness increased with each brighten response was unpredictable, and the monkeys could choose to classify the images at any time during a trial. We hypothesized that if monkeys monitored the status of their classification decision then they would seek information depending on the amount of information available. In Experiment 1, monkeys rarely used the brighten response when images were bright initially, and they used the brighten response more when earlier uses in a given trial yielded smaller amounts of information. In Experiment 2, monkeys made more brighten responses when the presented image did not belong in any of the trained categories, suggesting monkeys were sensitive to the fact that they could not reach a classification decision despite the image brightening. In Experiment 3, we found that the probability that monkeys used the brighten response correlated with their ability to correctly classify when the brighten response was not available. These findings add to the literature documenting the metacognitive skills of nonhuman primates by demonstrating an iterative feedback loop between cognitive monitoring and cognitive control that allows for adaptive information-seeking behavior.

Launch! Self-agency as a discriminative cue for humans (Homo sapiens) and monkeys (Macaca Mulatta)

Self-agency is a crucial aspect of self-awareness. It is underresearched given the phenomenon's subjectivity and difficulty of study. It is particularly underresearched comparatively, given that animals cannot receive agency instructions or make agency declarations. Accordingly, we developed a distinctively new self-agency paradigm. Humans and rhesus macaques learned event categories differentiated by whether the participant's volitional response controlled a screen launch. They learned by trial and error after minimal instructions with no agency orientation (humans) or no instructions (monkeys). After learning, humans' verbalized category descriptions were coded for self-agency attributions. Across three experiments, humans' agency attributions qualitatively improved discrimination performance-participants not invoking self-agency rarely exceeded chance performance. It also produced a diagnostic latency profile: classification accuracy depended heavily on the temporal relationship between the button-press and the launch, but only for those invoking agency. In our last experiment, monkeys performed the launch task. Their performance and latency profiles mirrored that of humans. Thus, self-agency can be self-discovered as a frame organizing discrimination. And it may be used as a discrimination cue by some nonhuman animals as well. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Are there Metacognitivists in the Fox Hole? A Preliminary Test of Information Seeking in an Arctic Fox (Vulpes lagopus)

Over the last two decades, evidence has accrued that at least some nonhuman animals possess metacognitive abilities. However, of the carnivores, only domestic dogs have been tested. Although rarely represented in the psychological literature, foxes are good candidates for metacognition given that they cache their food. Two experiments assessed metacognition in one male arctic fox (Vulpes lagopus) for the first time. An information-seeking paradigm was used, in which the subject had the opportunity to discover which compartment was baited before making a choice by looking through a transparent window in the apparatus. In the first experiment, choice accuracy during seen trials was equal to choice accuracy on unseen trials. Importantly, there was no significant difference between the subject's looking behavior on seen versus unseen trials. In the second experiment, with chance probabilities reduced, the subject's choice accuracy on both seen and unseen trials was below chance. The subject did not exhibit looking behavior in any of the trials. Latencies to choose were not influenced by whether he witnessed baiting. Although we did not obtain evidence of metacognition in our tests of a single subject, we maintain that foxes may be good candidates for further tests using similar methodologies to those introduced here.

Capuchin monkeys (sometimes) go when they know: Confidence movements in Sapajus apella

To test for evidence of metacognition in capuchin monkeys (Sapajus apella), we analyzed confidence movements using a paradigm adapted from research with chimpanzees. Capuchin monkeys provide an interesting model species for the comparative assessment of metacognition as they show limited evidence of such cognitive-monitoring processes in a variety of metacognition paradigms. Here, monkeys were presented with a computerized delayed matching-to-sample (DMTS) memory test in one location but were rewarded for correct responses in a separate location. Movements could be made from one location to the other at any time, but movements between a response and reward feedback may reflect confidence in the accuracy of the response. Critically, DMTS tests included occasional "no sample" trials where monkeys' performance was at chance when the trial started without a sample and a 1-s interval to the response options. We predicted that monkeys would (1) perform less accurately (and less confidently) at longer retention intervals, (2) move to the dispenser early more often on trials completed correctly than incorrectly, and (3) show a relation between faster response latency and early movements. Analyses of response times and "go" or "no go" confidence movements before feedback to the reward location suggested that the monkeys were capable of monitoring confidence in their responses. However, their confidence movements were less precise and less flexible than chimpanzees. Overall, this paradigm can reveal potential metacognitive abilities in nonhuman animals that otherwise demonstrate these abilities inconsistently.

Capuchin monkeys (Sapajus apella) failed to seek information for their potential forgetting in a computerized task

Memory is always vulnerable to loss because it fades over time. To avoid the potential loss of a particular memory, individuals who can anticipate this loss might seek an opportunity to re-encode the information at the later point. Evidence shows that animals engage in online memory monitoring, but few studies have addressed whether they seek information prospectively to guard against potential forgetting. In the present study, to address this issue three capuchin monkeys were tested using a delayed matching-to-sample task with a cue signaling delay length (short or long). In the tests, subjects could choose at the onset of the delay whether or not to seek a re-presentation of a sample after the delay. Results showed that two monkeys sought re-presentation in the long delay more frequently than in the short delay, suggesting knowledge of the necessity of re-presentation based on knowing the length of the delay. However, further tests provided no evidence that this response was based on metacognitive cues. Whether capuchin monkeys are capable of prospective information-seeking for own potential forgetting remains to be established.

Explicit memory and cognition in monkeys

Taxonomies of human memory, influenced heavily by Endel Tulving, make a fundamental distinction between explicit and implicit memory. Humans are aware of explicit memories, whereas implicit memories control behavior even though we are not aware of them. Efforts to understand the evolution of memory, and to use nonhuman animals to model human memory, will be facilitated by better understanding the extent to which this critical distinction exists in nonhuman animals. Work with metacognition paradigms in the past 20 years has produced a strong case for the existence of explicit memory in nonhuman primates and possibly other nonhuman animals. Clear dissociations of explicit and implicit memory by metacognition have yet to be demonstrated in nonhumans, although dissociations between memory systems by other behavioral techniques, and by brain manipulations, suggest that the explicit-implicit distinction applies to nonhumans. Neurobehavioral studies of metamemory are beginning to identify neural substrates for memory monitoring in the frontal cortex of monkeys. We have strong evidence that at least some memory systems are explicit in rhesus monkeys, but we need to learn more about the distribution of explicit processes across cognitive systems within monkeys, and across species.

Monkey Metacognition Could Generate More Insight

Monkeys demonstrate metacognition by avoiding memory tests when they forget, seeking information when ignorant, and gambling sensibly after making judgments. Some of this metacognition appears to be based on introspection of private mental states. It is likely that nonhuman cognitive systems, like human systems, differ in accessibility to such introspective metacognition, and the extent to which differences in access map to explicit and implicit cognition will be an important topic for future work. It will be exciting to learn more about the distribution of metacognition among species, and the conditions under which metacognition evolves.

Capuchin and rhesus monkeys but not humans show cognitive flexibility in an optional-switch task

Learned rules help us accurately solve many problems, but by blindly following a strategy, we sometimes fail to find more efficient alternatives. Previous research found that humans are more susceptible to this "cognitive set" bias than other primates in a nonverbal computer task. We modified the task to test one hypothesis for this difference, that working memory influences the advantage of taking a shortcut. During training, 60 humans, 7 rhesus macaques, and 22 capuchin monkeys learned to select three icons in sequence. They then completed 96 baseline trials, in which only this learned rule could be used, and 96 probe trials, in which they could also immediately select the final icon. Rhesus and capuchin monkeys took this shortcut significantly more often than humans. Humans used the shortcut more in this new, easier task than in previous work, but started using it significantly later than the monkeys. Some participants of each species also used an intermediate strategy; they began the learned rule but switched to the shortcut after selecting the first item in the sequence. We suggest that these species differences arise from differences in rule encoding and in the relative efficiency of exploiting a familiar strategy versus exploring alternatives.

Dissociation of memory signals for metamemory in rhesus monkeys (Macaca mulatta)

Some nonhuman species demonstrate metamemory, the ability to monitor and control memory. Here, we identify memory signals that control metamemory judgments in rhesus monkeys by directly comparing performance in two metamemory paradigms while holding the availability of one memory signal constant and manipulating another. Monkeys performed a four-choice match-to-sample memory task. In Experiment 1, monkeys could decline memory tests on some trials for a small, guaranteed reward. In Experiment 2, monkeys could review the sample on some trials. In both experiments, monkeys improved accuracy by selectively declining tests or reviewing samples when memory was poor. To assess the degree to which different memory signals made independent contributions to the metamemory judgement, we made the decline-test or review-sample response available either prospectively, before the test, or concurrently with test stimuli. Prospective metamemory judgements are likely controlled by the current contents of working memory, whereas concurrent metamemory judgements may also be controlled by additional relative familiarity signals evoked by the sight of the test stimuli. In both paradigms, metacognitive responding enhanced accuracy more on concurrent than on prospective tests, suggesting additive contributions of working memory and stimulus-evoked familiarity. Consistent with the hypothesis that working memory and stimulus-evoked familiarity both control metamemory judgments when available, metacognitive choice latencies were longer in the concurrent condition, when both were available. Together, these data demonstrate that multiple memory signals can additively control metacognitive judgements in monkeys and provide a framework for mapping the interaction of explicit memory signals in primate memory.

I scan, therefore I decline: The time course of difficulty monitoring in humans (homo sapiens) and macaques (macaca mulatta)

The study of nonhumans' metacognitive judgments about trial difficulty has grown into an important comparative literature. However, the potential for associative-learning confounds in this area has left room for behaviorist interpretations that are strongly asserted and hotly debated. This article considers how researchers may be able to observe animals' strategic cognitive processes more clearly by creating temporally extended problems within which associative cues are not always immediately available. We asked humans and rhesus macaques to commit to completing spatially extended mazes or to decline completing them through a trial-decline response. The mazes could sometimes be completed successfully, but other times had a constriction that blocked completion. A deliberate, systematic scanning process could preevaluate a maze and determine the appropriate response. Latency analyses charted the time course of the evaluative process. Both humans and macaques appeared, from the pattern of their latencies, to scan the mazes through before committing to completing them. Thus monkeys, too, can base trial-decline responses on temporally extended evaluation processes, confirming that those responses have strategic cognitive-processing bases in addition to behavioral-reactive bases. The results also show the value of temporally and spatially extended problems to let researchers study the trajectory of animals' online cognitive processes. (PsycINFO Database Record

Chimpanzees show some evidence of selectively acquiring information by using tools, making inferences, and evaluating possible outcomes

Metacognition refers to thinking about one's thinking or knowing what one knows. Research suggests that this ability is not unique to humans and may be shared with nonhuman animals. In particular, great apes have shown behaviors on a variety of tasks that are suggestive of metacognitive ability. Here we combine a metacognitive task, the information-seeking task, with tool use and variable forms of initial information provided to chimpanzees to explore how informational states impact behavioral responses in these apes. Three chimpanzees were presented with an apparatus that contained five locations where food could be hidden. If they pointed to the correct location, they received the reward, but otherwise they did not. We first replicated several existing findings using this method, and then tested novel hypotheses. The chimpanzees were given different types of information across the experiments. Sometimes, they were shown the location of the food reward. Other times, they were shown only one empty location, which was not useful information. The chimpanzees also could use a tool to search any of those locations before making a selection. Chimpanzees typically used the tool to search out the location of the reward when they could not already know where it was, but they did not use the tool when they already had been given that information. One chimpanzee made inferences about the location of hidden food, even when that food was never shown in that location. The final experiment involved hiding foods of differing preference values, and then presenting the chimpanzees with different initial knowledge states (i.e., where the best food was located, where the less-preferred food was located, or where no food was located). All chimpanzees used the tool when they needed to use it to find the best possible item on that trial, but responded by choosing a location immediately when they did not need the tool. This finding highlights that their behavior was not the result of a simple rule following such as pointing to where any food had been seen.

The transfer of category knowledge by macaques (Macaca mulatta) and humans (Homo sapiens)

Cognitive psychologists distinguish implicit, procedural category learning (stimulus-response associations learned outside declarative cognition) from explicit-declarative category learning (conscious category rules). These systems are dissociated by category learning tasks with either a multidimensional, information-integration (II) solution or a unidimensional, rule-based (RB) solution. In the present experiments, humans and two monkeys learned II and RB category tasks fostering implicit and explicit learning, respectively. Then they received occasional transfer trials-never directly reinforced-drawn from untrained regions of the stimulus space. We hypothesized that implicit-procedural category learning-allied to associative learning-would transfer weakly because it is yoked to the training stimuli. This result was confirmed for humans and monkeys. We hypothesized that explicit category learning-allied to abstract category rules-would transfer robustly. This result was confirmed only for humans. That is, humans displayed explicit category knowledge that transferred flawlessly. Monkeys did not. This result illuminates the distinctive abstractness, stimulus independence, and representational portability of humans' explicit category rules. (PsycINFO Database Record

Formal models in animal-metacognition research: the problem of interpreting animals' behavior

Ongoing research explores whether animals have precursors to metacognition-that is, the capacity to monitor mental states or cognitive processes. Comparative psychologists have tested apes, monkeys, rats, pigeons, and a dolphin using perceptual, memory, foraging, and information-seeking paradigms. The consensus is that some species have a functional analog to human metacognition. Recently, though, associative modelers have used formal-mathematical models hoping to describe animals' "metacognitive" performances in associative-behaviorist ways. We evaluate these attempts to reify formal models as proof of particular explanations of animal cognition. These attempts misunderstand the content and proper application of models. They embody mistakes of scientific reasoning. They blur fundamental distinctions in understanding animal cognition. They impede theoretical development. In contrast, an energetic empirical enterprise is achieving strong success in describing the psychology underlying animals' metacognitive performances. We argue that this careful empirical work is the clear path to useful theoretical development. The issues raised here about formal modeling-in the domain of animal metacognition-potentially extend to biobehavioral research more broadly.

A metacognitive illusion in monkeys

Like humans, monkeys can make accurate judgements about their own memory by reporting their confidence during cognitive tasks. Some have suggested that animals use associative learning to make accurate confidence judgements, while others have suggested animals directly access and estimate the strength of their memories. Here we test a third, non-exclusive possibility: perhaps monkeys, like humans, base metacognitive inferences on heuristic cues. Humans are known to use cues like perceptual fluency (e.g. how easy something is to see) when making metacognitive judgements. We tested monkeys using a match-to-sample task in which the perceptual fluency of the stimuli was manipulated. The monkeys made confidence wagers on their accuracy before or after each trial. We found that monkeys' wagers were affected by perceptual fluency even when their accuracy was not. This is novel evidence that animals are susceptible to metacognitive illusions similar to those experienced by humans.

Information seeking about tool properties in great apes

Evidence suggests that great apes engage in metacognitive information seeking for food items. To support the claim that a domain-general cognitive process underlies ape metacognition one needs to show that selective information seeking extends to non-food items. In this study, chimpanzees (Pan troglodytes) and orangutans (Pongo abelii) either had to determine the location of a desired food item or a property of a non-food item (length of a tool). We manipulated whether subjects received prior information about the item's location or property. During the test, subjects had the opportunity to seek the respective information. Results show that apes engaged in more information seeking when they had no prior knowledge. Importantly, this selective pattern of information seeking applied to food as well as to tools.

Checking behavior in rhesus monkeys is related to anxiety and frontal activity

When facing doubt, humans can go back over a performed action in order to optimize subsequent performance. The present study aimed to establish and characterize physiological doubt and checking behavior in non-human primates (NHP). We trained two rhesus monkeys (Macaca mulatta) in a newly designed “Check-or-Go” task that allows the animal to repeatedly check and change the availability of a reward before making the final decision towards obtaining that reward. By manipulating the ambiguity of a visual cue in which the reward status is embedded, we successfully modulated animal certainty and created doubt that led the animals to check. This voluntary checking behavior was further characterized by making EEG recordings and measuring correlated changes in salivary cortisol. Our data show that monkeys have the metacognitive ability to express voluntary checking behavior similar to that observed in humans, which depends on uncertainty monitoring, relates to anxiety and involves brain frontal areas.

Primate cognition: attention, episodic memory, prospective memory, self-control, and metacognition as examples of cognitive control in nonhuman primates

Primate Cognition is the study of cognitive processes, which represent internal mental processes involved in discriminations, decisions, and behaviors of humans and other primate species. Cognitive control involves executive and regulatory processes that allocate attention, manipulate and evaluate available information (and, when necessary, seek additional information), remember past experiences to plan future behaviors, and deal with distraction and impulsivity when they are threats to goal achievement. Areas of research that relate to cognitive control as it is assessed across species include executive attention, episodic memory, prospective memory, metacognition, and self-control. Executive attention refers to the ability to control what sensory stimuli one attends to and how one regulates responses to those stimuli, especially in cases of conflict. Episodic memory refers to memory for personally experienced, autobiographical events. Prospective memory refers to the formation and implementation of future-intended actions, such as remembering what needs to be done later. Metacognition consists of control and monitoring processes that allow individuals to assess what information they have and what information they still need, and then if necessary to seek information. Self-control is a regulatory process whereby individuals forego more immediate or easier to obtain rewards for more delayed or harder to obtain rewards that are objectively more valuable. The behavioral complexity shown by nonhuman primates when given tests to assess these capacities indicates psychological continuities with human cognitive control capacities. However, more research is needed to clarify the proper interpretation of these behaviors with regard to possible cognitive constructs that may underlie such behaviors. WIREs Cogn Sci 2016, 7:294-316. doi: 10.1002/wcs.1397 For further resources related to this article, please visit the WIREs website.

Self-control assessments of capuchin monkeys with the rotating tray task and the accumulation task

Recent studies of delay of gratification in capuchin monkeys using a rotating tray (RT) task have shown improved self-control performance in these animals in comparison to the accumulation (AC) task. In this study, we investigated whether this improvement resulted from the difference in methods between the rotating tray task and previous tests, or whether it was the result of greater overall experience with delay of gratification tasks. Experiment 1 produced similar performance levels by capuchins monkeys in the RT and AC tasks when identical reward and temporal parameters were used. Experiment 2 demonstrated a similar result using reward amounts that were more similar to previous AC experiments with these monkeys. In Experiment 3, monkeys performed multiple versions of the AC task with varied reward and temporal parameters. Their self-control behavior was found to be dependent on the overall delay to reward consumption, rather than the overall reward amount ultimately consumed. These findings indicate that these capuchin monkeys' self-control capacities were more likely to have improved across studies because of the greater experience they had with delay of gratification tasks. Experiment 4 and Experiment 5 tested new, task-naïve monkeys on both tasks, finding more limited evidence of self-control, and no evidence that one task was more beneficial than the other in promoting self-control. The results of this study suggest that future testing of this kind should focus on temporal parameters and reward magnitude parameters to establish accurate measures of delay of gratification capacity and development in this species and perhaps others.

Comparing species decisions in a dichotomous choice task: adjusting task parameters improves performance in monkeys

In comparative psychology, both similarities and differences among species are studied to better understand the evolution of their behavior. To do so, we first test species in tasks using similar procedures, but if differences are found, it is important to determine their underlying cause(s) (e.g., are they due to ecology, cognitive ability, an artifact of the study, and/or some other factor?). In our previous work, primates performed unexpectedly poorly on an apparently simple two-choice discrimination task based on the natural behavior of cleaner fish, while the fish did quite well. In this task, if the subjects first chose one of the options (ephemeral) they received both food items, but if they chose the other (permanent) option first, the ephemeral option disappeared. Here, we test several proposed explanations for primates' relatively poorer performance. In Study 1, we used a computerized paradigm that differed from the previous test by removing interaction with human experimenters, which may be distracting, and providing a more standardized testing environment. In Study 2, we adapted the computerized paradigm from Study 1 to be more relevant to primate ecology. Monkeys' overall performance in these adapted tasks matched the performance of the fish in the original study, showing that with the appropriate modifications they can solve the task. We discuss these results in light of comparative research, which requires balancing procedural similarity with considerations of how the details of the task or the context may influence how different species perceive and solve tasks differently.

Capuchin monkeys (Cebus apella) modulate their use of an uncertainty response depending on risk

Metacognition refers to thinking about thinking, and there has been a great deal of interest in how this ability manifests across primates. Based on much of the work to date, a tentative division has been drawn with New World monkeys on 1 side and Old World monkeys and apes on the other. Specifically, Old World monkeys, apes, and humans often show patterns reflecting metacognition, but New World monkeys typically do not, or show less convincing behavioral patterns. However, recent data suggest that this difference may relate to other aspects of some experimental tasks. For example, 1 possibility is that risk tolerance affects how capuchin monkeys, a New World primate species, tend to perform. Specifically, it has recently been argued that on tasks in which there are 2 or 3 options, the "risk" of guessing is tolerable for capuchins because there is a high probability of being correct even if they "know they do not know" or feel something akin to uncertainty. The current study investigated this possibility by manipulating the degree of risk (2-choices vs. 6-choices) and found that capuchin monkeys used the uncertainty response more on 6-choice trials than on 2-choice trials. We also found that rate of reward does not appear to underlie these patterns of performance, and propose that the degree of risk is modulating capuchin monkeys' use of the uncertainty response. Thus, the apparent differences between New and Old World monkeys in metacognition may reflect differences in risk tolerance rather than access to metacognitive states.

Rhesus monkeys (Macaca mulatta) adaptively adjust information seeking in response to information accumulated

Metacognition consists of monitoring and control processes. Monitoring has been inferred when nonhumans use a "decline test" response to selectively escape difficult test trials. Cognitive control has been inferred from selective information-seeking behavior by nonhumans ignorant of needed knowledge. Here we describe a computerized paradigm that extends previous work and assesses dynamic interactions between monitoring and control. Monkeys classified images as containing birds, fish, flowers, or people. To-be-classified images were initially masked, and monkeys were trained to gradually reveal the images by touching a "reveal button." Monkeys could choose to classify images at any time or to reveal more of the images. Thus, they had the opportunity to assess when enough of an image had been revealed to support accurate classification. In Experiment 1, monkeys made more reveal responses before classifying when smaller amounts of the image were revealed by each button touch. In Experiment 2, to-be-classified images were shrunk and covered by 1 critical blocker among other blockers that did not provide information when removed. Monkeys made more reveal responses as the critical blocker was removed later in the trial. In Experiment 3, monkeys were presented with previously classified images with either more or fewer blockers obscuring the image than was the case when they chose to classify that image previously. Monkeys made more reveal responses when information was insufficient than when it was excessive. These results indicate that monkeys dynamically monitor evolving decision processes and adaptively collect information as necessary to maintain accuracy.

Assessment of metacognitive monitoring and control in baboons (Papio papio)

Metacognition refers to the ability of an organism to evaluate its states of knowledge (metacognitive monitoring) and engage in appropriate information-seeking behaviors when a lack of knowledge is detected (metacognitive control). This study assessed metacognitive monitoring and control in three Guinea baboons (Papio papio). Monkeys were required to report on a touchscreen the location of two target stimuli that had previously appeared briefly on a grid. They could either respond directly or use a "Repeat" key providing an opportunity to repeat the target stimuli. In Experiment 1, the baboons used the Repeat key more frequently in difficult trials and transferred this use of the key to novel conditions. Two baboons showed higher accuracy when they declined using the key compared to Baseline trials in which the key was not available, suggesting accurate metacognitive monitoring judgments. The same two baboons were consistently faster at reporting the targets' locations after a repetition of the stimulus. In Experiment 2, the baboons had to choose between two Repeat keys, one for each target. Two baboons showed a preference for repeating the presentation of the less visible target, suggesting that they identified what information they lack. Overall, results support the hypothesis of metacognitive monitoring in baboons, and also provide limited evidence for metacognitive control. We propose that tests requiring subjects to choose between several metacognitive responses in computerized tasks provide a suitable new approach for studying targeted information-seeking behaviors in animals.

Go when you know: Chimpanzees' confidence movements reflect their responses in a computerized memory task

Three chimpanzees performed a computerized memory task in which auditory feedback about the accuracy of each response was delayed. The delivery of food rewards for correct responses also was delayed and occurred in a separate location from the response. Crucially, if the chimpanzees did not move to the reward-delivery site before food was dispensed, the reward was lost and could not be recovered. Chimpanzees were significantly more likely to move to the dispenser on trials they had completed correctly than on those they had completed incorrectly, and these movements occurred before any external feedback about the outcome of their responses. Thus, chimpanzees moved (or not) on the basis of their confidence in their responses, and these confidence movements aligned closely with objective task performance. These untrained, spontaneous confidence judgments demonstrated that chimpanzees monitored their own states of knowing and not knowing and adjusted their behavior accordingly.

Looking ahead? Computerized maze task performance by chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta), capuchin monkeys (Cebus apella), and human children (Homo sapiens)

Human and nonhuman primates are not mentally constrained to the present. They can remember the past and-at least to an extent-anticipate the future. Anticipation of the future ranges from long-term prospection such as planning for retirement to more short-term future-oriented cognition such as planning a route through a maze. Here we tested a great ape species (chimpanzees), an Old World monkey species (rhesus macaques), a New World monkey species (capuchin monkeys), and human children on a computerized maze task. All subjects had to move a cursor through a maze to reach a goal at the bottom of the screen. For best performance on the task, subjects had to "plan ahead" to the end of the maze to move the cursor in the correct direction, avoid traps, and reverse directions if necessary. Mazes varied in difficulty. Chimpanzees were better than both monkey species, and monkeys showed a particular deficit when moving away from the goal or changing directions was required. Children showed a similar pattern to monkeys regarding the effects of reversals and moves away from the goal, but their overall performance in terms of correct maze completion was similar to the chimpanzees. The results highlight similarities as well as differences in planning across species and the role that inhibitory control may play in future-oriented cognition in primates.

Evaluation of seven hypotheses for metamemory performance in rhesus monkeys

Knowing the extent to which nonhumans and humans share mechanisms for metacognition will advance our understanding of cognitive evolution and will improve selection of model systems for biomedical research. Some nonhuman species avoid difficult cognitive tests, seek information when ignorant, or otherwise behave in ways consistent with metacognition. There is agreement that some nonhuman animals "succeed" in these metacognitive tasks, but little consensus about the cognitive mechanisms underlying performance. In one paradigm, rhesus monkeys visually searched for hidden food when ignorant of the location of the food, but acted immediately when knowledgeable. This result has been interpreted as evidence that monkeys introspectively monitored their memory to adaptively control information seeking. However, convincing alternative hypotheses have been advanced that might also account for the adaptive pattern of visual searching. We evaluated seven hypotheses using a computerized task in which monkeys chose either to take memory tests immediately or to see the answer again before proceeding to the test. We found no evidence to support the hypotheses of behavioral cue association, rote response learning, expectancy violation, response competition, generalized search strategy, or postural mediation. In contrast, we repeatedly found evidence to support the memory monitoring hypothesis. Monkeys chose to see the answer when memory was poor, either from natural variation or experimental manipulation. We found limited evidence that monkeys also monitored the fluency of memory access. Overall, the evidence indicates that rhesus monkeys can use memory strength as a discriminative cue for information seeking, consistent with introspective monitoring of explicit memory.

Information seeking in capuchins (Cebus apella): a rudimentary form of metacognition?

In previous research, great apes and rhesus macaques have demonstrated multiple apparently metacognitive abilities, whereas capuchin monkeys have not. The present experiment investigated whether at least a rudimentary form of metacognition might be demonstrated in capuchins if a simplified metacognitive task was used. Capuchins (Cebus apella) were required to locate a food reward hidden beneath one of two inverted cups that sat on a Plexiglas tray. In some conditions, the capuchins were shown where the food was hidden, in others they could infer its location, and in yet others they were not given information about the location of the food. On all trials, capuchins could optionally seek information about the food's location by looking up through the Plexiglas beneath the cups. In general, capuchins did this less often when they were shown the food reward, but not when they could infer the reward's location. These data suggest that capuchins-if metacognitive-only metacognitively control their information seeking in some conditions, particularly those in which information is presented in the visual domain. This may represent a rudimentary version of metacognitive control, in comparison with that seen in great apes and humans.

Exploring Potential Mechanisms Underlying the Lack of Uncertainty Monitoring in Capuchin Monkeys

In a widely used animal-metacognition paradigm, monkeys are positively reinforced with food for correct classifications of stimuli as sparse or dense and punished with timeouts for incorrect responses, but they also have access to an "uncertainty" response that moves them to the next trial without either of these forms of feedback. Rhesus monkeys use this uncertainty response most often for trials on which they are at greatest risk for making an error, suggesting that they are monitoring their ability to make these classifications. Capuchin monkeys do not succeed to the same degree on these tasks-conceivably as a result of differential contingencies in place in all existing studies between the sparse/dense responses (food delivery or timeout) and the uncertainty response (avoidance of a timeout but also no chance for food reward). Here, we used a novel variation of this task in which the outcomes of the three response classes (sparse, dense, uncertain) were functionally equivalent. All responses simply determined the delay interval before presentation of a second task (matching-to-sample), and that task yielded potential food rewards. Overall, capuchin monkeys used the dense and sparse responses appropriately, including some animals that had no prior experience in performing this classification task. However, none used the uncertainty response appropriately even when it was placed on the same contingency plane as the dense and sparse responses. This suggests that the failure of capuchin monkeys to use an uncertainty response is not the result of that response producing a qualitatively different outcome compared to the dense and sparse responses.

The misbehaviour of a metacognitive monkey

Metacognition, the monitoring of one's own mental states, is a fundamental aspect of human intellect. Despite tests in nonhuman animals suggestive of uncertainty monitoring, some authors interpret these results solely in terms of primitive psychological mechanisms and reinforcement regimes, where "reinforcement" is invariably considered to be the delivery and consumption of earned food rewards. Surprisingly, few studies have detailed the trial-by-trial behaviour of animals engaged in such tasks. Here we report ethology-based observations on a rhesus monkey completing sparse-dense discrimination problems, and given the option of escaping trials (i.e., responding "uncertain") at its own choosing. Uncertainty responses were generally made on trials of high objective difficulty, and were characterized by long latencies before beginning visible trials, long times taken for response, and, even after controlling for difficulty, high degrees of wavering during response. Incorrect responses were also common in trials of high objective difficulty, but were characterized by low degrees of wavering. This speaks to the likely adaptive nature of "hesitation," and is inconsistent with models which argue or predict implicit, inflexible information-seeking or "alternative option" behaviours whenever challenging problems present themselves, Confounding models which suggest that nonhuman behaviour in metacognition tasks is driven solely by food delivery/consumption, the monkey was also observed allowing pellets to accumulate and consuming them during and after trials of all response/outcome categories (i.e., whether correct, incorrect, or escaped). This study thus bolsters previous findings that rhesus monkey behaviour in metacognition tasks is in some respects disassociated from mere food delivery/consumption, or even the avoidance of punishment. These and other observations fit well with the evolutionary status and natural proclivities of rhesus monkeys, but weaken arguments that responses in such tests are solely associated with associative mechanisms, and instead suggest more derived and controlled cognitive processing. The latter interpretation appears particularly parsimonious given the neurological adaptations of primates, as well as their highly flexible social and ecological behaviour.

Cashing out: The decisional flexibility of uncertainty responses in rhesus macaques (Macaca mulatta) and humans (Homo sapiens)

Researchers are exploring whether animals share with humans something like a metacognitive capacity. Though some results point to human-animal continuities in this domain, they face the dominant criticism that animals' performances might be associative. A persistent problem is that animal-metacognition paradigms present static environments of risk and reward that may foster inflexible and conditioned responding. Those environments do not challenge animals to show the flexibility in their decision strategies that could indicate an antecedent capacity to metacognition. Accordingly, we tested macaques and humans on an uncertainty-monitoring paradigm in which risk changed dynamically. Participants classified stimuli of different difficulties while also choosing when to use a cashout response to collect the accumulated rewards that would be forfeit on a discrimination error. Macaques (Macaca mulatta) and humans flexibly adjusted their decision criteria to achieve appropriate protection against the cost of error that could differ depending on trial difficulty and the number of rewards at risk. In particular, monkeys widened their cashout-response region as their accumulated rewards increased, providing more protection against a more costly error. These findings demonstrate a new continuity between humans' and animals' uncertainty systems. They reveal a calibration by macaques of present risk to trial difficulty tolerated. They show that animals' uncertainty-monitoring and risk-management systems have substantial trial-by-trial flexibility.

What are my chances? Closing the gap in uncertainty monitoring between rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella)

Previous studies have indicated that rhesus monkeys (Macaca mulatta) but not capuchin monkeys (Cebus apella) respond to difficult or ambiguous situations by choosing not to respond or by seeking more information. Here we assessed whether a task with very low chance accuracy could diminish this species difference, presumably indicating that capuchins—compared to macaques—are less risk averse as opposed to less sensitive to signals of uncertainty. Monkeys searched for the largest of 6 stimuli on a computer screen. Trial difficulty was varied, and monkeys could choose to opt out of any trial. All rhesus monkeys, including some with no prior use of the uncertainty response, selectively avoided the most difficult trials. The majority of capuchins sometimes made uncertainty responses, but at lower rates than rhesus monkeys. Nonetheless, the presence of some adaptive uncertainty responding suggests that capuchins also experience uncertainty and can respond to it, though with less proficiency than macaque monkeys.

Metacognitive-like information seeking in lion-tailed macaques: a generalized search response after all?

Previous research has demonstrated that Old World primates (both apes and monkeys) seek information about the location of a hidden food item, unless they are privy to the hiding process. This has been cited as evidence of metacognition. However, these results could also be interpreted using non-metacognitive accounts, including a generalized search response to uncertainty, in which subjects reach for food when it is seen, or search for food until it is spotted. In the present research, lion-tailed macaques were tested on an object-choice task. Conditions varied with respect to the visibility of the baiting process, and whether the location of the hidden food could be inferred by logical exclusion. Additionally, the hidden food could be located visually before a choice was made, by peering under the objects through a Plexiglas tray. Across conditions, monkeys consistently looked for the food when it had not been seen, even if its location could be inferred, despite the fact that these monkeys are capable of inference by exclusion. This suggests that apparently 'metacognitive' information seeking in monkeys may instead reflect a generalized search strategy. Alternatively, it is possible that monkeys only have metacognitive access to certain types of knowledge, including that obtained visually. Results are discussed with respect to the likelihood of metacognition in this species and the evolutionary emergence of metacognition across species.

Animal metacognition: a tale of two comparative psychologies

A growing literature considers whether animals have capacities that are akin to human metacognition (i.e., humans' capacity to monitor their states of uncertainty and knowing). Comparative psychologists have approached this question by testing a dolphin, pigeons, rats, monkeys, and apes using perception, memory, and food-concealment paradigms. As part of this consideration, some associative modelers have attempted to describe animals' "metacognitive" performances in low-level, associative terms-an important goal if achievable. The authors summarize the empirical and theoretical situation regarding these associative descriptions. The associative descriptions in the animal-metacognition literature fail to encompass important phenomena. The sharp focus on abstract, mathematical associative models creates serious interpretative problems. The authors compare these failed associative descriptions with an alternative theoretical approach within contemporary comparative psychology. The alternative approach has the potential to strengthen comparative psychology as an empirical science and integrate it more fully within the mainstream of experimental psychology and cognitive science.

Working and waiting for better rewards: self-control in two monkey species (Cebus apella and Macaca mulatta)

Self-control is typically defined as choosing a greater, delayed reward over a lesser, more immediate reward. However, in nature, there are other costs besides delay associated with obtaining the greatest outcome including increased effort, potential punishment, and low probability of reward. Effort is an interesting case because it sometimes impairs self-control, by acting as an additional cost, and at other times facilitates self-control, by distracting one from impulsive options. Additionally, different species may perform differently in effortful self-control tasks, based on their natural ecology. To gain insight into these aspects of self-control behavior, we examined capuchin monkeys' and rhesus monkeys' self-control in separate working and waiting choice tasks. We hypothesized that capuchins would show greater self-control in the working task, given their naturally higher activity level, whereas rhesus would perform similarly in both tasks. Rhesus performed as predicted, whereas contrary to our hypothesis, capuchins exhibited lesser performance in the working task. Nonetheless, these results may still stem from inherent species differences interacting with details of the methodology. Capuchins, being highly energetic and social monkeys, may have divided their energy and attention between the working task and other elements of the test environment such as visible group mates or manipulanda.

Supra-personal cognitive control and metacognition

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We propose a ‘dual systems’ framework for thinking about metacognition.

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System 1 metacognition is for ‘intra-personal’ cognitive control.

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System 2 metacognition is for ‘supra-personal’ cognitive control.

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The latter allows agents to share metacognitive representations.

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This sharing creates benefits for the group and facilitates cumulative culture.

The human mind is extraordinary in its ability not merely to respond to events as they unfold but also to adapt its own operation in pursuit of its agenda. This ‘cognitive control’ can be achieved through simple interactions among sensorimotor processes, and through interactions in which one sensorimotor process represents a property of another in an implicit, unconscious way. So why does the human mind also represent properties of cognitive processes in an explicit way, enabling us to think and say ‘I’m sure’ or ‘I’m doubtful’? We suggest that ‘system 2 metacognition’ is for supra-personal cognitive control. It allows metacognitive information to be broadcast, and thereby to coordinate the sensorimotor systems of two or more agents involved in a shared task.

Do capuchin monkeys (Cebus apella) diagnose causal relations in the absence of a direct reward?

We adapted a method from developmental psychology to explore whether capuchin monkeys (Cebus apella) would place objects on a "blicket detector" machine to diagnose causal relations in the absence of a direct reward. Across five experiments, monkeys could place different objects on the machine and obtain evidence about the objects' causal properties based on whether each object "activated" the machine. In Experiments 1-3, monkeys received both audiovisual cues and a food reward whenever the machine activated. In these experiments, monkeys spontaneously placed objects on the machine and succeeded at discriminating various patterns of statistical evidence. In Experiments 4 and 5, we modified the procedure so that in the learning trials, monkeys received the audiovisual cues when the machine activated, but did not receive a food reward. In these experiments, monkeys failed to test novel objects in the absence of an immediate food reward, even when doing so could provide critical information about how to obtain a reward in future test trials in which the food reward delivery device was reattached. The present studies suggest that the gap between human and animal causal cognition may be in part a gap of motivation. Specifically, we propose that monkey causal learning is motivated by the desire to obtain a direct reward, and that unlike humans, monkeys do not engage in learning for learning's sake.

Comparative Cognition: Past, Present, and Future

Comparative cognition is the field of inquiry concerned with understanding the cognitive abilities and mechanisms that are evident in nonhuman species. Assessments of animal cognition have a long history, but in recent years there has been an explosion of new research topics, and a general broadening of the phylogenetic map of animal cognition. To review the past of comparative cognition, we describe the historical trends. In regards to the present state, we examine current "hot topics" in comparative cognition. Finally, we offer our unique and combined thoughts on the future of the field.

Honey bees selectively avoid difficult choices

Human decision-making strategies are strongly influenced by an awareness of certainty or uncertainty (a form of metacognition) to increase the chances of making a right choice. Humans seek more information and defer choosing when they realize they have insufficient information to make an accurate decision, but whether animals are aware of uncertainty is currently highly contentious. To explore this issue, we examined how honey bees (Apis mellifera) responded to a visual discrimination task that varied in difficulty between trials. Free-flying bees were rewarded for a correct choice, punished for an incorrect choice, or could avoid choosing by exiting the trial (opting out). Bees opted out more often on difficult trials, and opting out improved their proportion of successful trials. Bees could also transfer the concept of opting out to a novel task. Our data show that bees selectively avoid difficult tasks they lack the information to solve. This finding has been considered as evidence that nonhuman animals can assess the certainty of a predicted outcome, and bees' performance was comparable to that of primates in a similar paradigm. We discuss whether these behavioral results prove bees react to uncertainty or whether associative mechanisms can explain such findings. To better frame metacognition as an issue for neurobiological investigation, we propose a neurobiological hypothesis of uncertainty monitoring based on the known circuitry of the honey bee brain.

Fading perceptual resemblance: a path for rhesus macaques (Macaca mulatta) to conceptual matching?

Cognitive, comparative, and developmental psychologists have long been intrigued by humans' and animals' capacity to respond to abstract relations like sameness and difference, because this capacity may underlie crucial aspects of cognition like analogical reasoning. Recently, this capacity has been explored in higher-order, relational matching-to-sample (RMTS) tasks in which humans and animals try to complete analogies of sameness and difference between disparate groups of items. The authors introduced a new paradigm to this area, by yoking the relational-matching cue to a perceptual-matching cue. Then, using established algorithms for shape distortion, the perceptual cue was weakened and eliminated. Humans' RMTS performance easily transcended the elimination of perceptual support. In contrast, RMTS performance by six macaques faltered as they were weaned from perceptual support. No macaque showed evidence of mature RMTS performance, even given more than 260,000 training trials during which we tried to coax a relational-matching performance from them. It is an important species difference that macaques show so hesitant a response to conceptual relations when humans respond to them so effortlessly. It raises theoretical questions about the emergence of this crucial capacity during humans' cognitive evolution and during humans' cognitive development.

Retrospective and prospective metacognitive judgments in rhesus macaques (Macaca mulatta)

A growing body of research suggests that some non-human animals are capable of making accurate metacognitive judgments. In previous studies, non-human animals have made either retrospective or prospective judgments (about how they did on a test or how they will do on a test, respectively). These two types of judgments are dissociable in humans. The current study tested the abilities of two rhesus macaque monkeys to make both retrospective and prospective judgments about their performance on the same memory task. Both monkeys had been trained previously to make retrospective confidence judgments. Both monkeys successfully demonstrated transfer of retrospective metacognitive judgments to the new memory task. Furthermore, both monkeys transferred their retrospective judgments to the prospective task (one, immediately, and one, following the elimination of a response bias). This study is the first to demonstrate both retrospective and prospective monitoring abilities in the same monkeys and on the same task, suggesting a greater level of flexibility in animals' metacognitive monitoring abilities than has been reported previously.

Executive-attentional uncertainty responses by rhesus macaques (Macaca mulatta)

The uncertainty response has been influential in studies of human perception, and it is crucial in the growing research literature that explores animal metacognition. However, the uncertainty response's interpretation is still sharply debated. The authors sought to clarify this interpretation using the dissociative technique of cognitive loads imposed on ongoing discrimination performance. Four macaques (Macaca mulatta) performed a sparse-dense discrimination within which an uncertainty response let them decline difficult trials or a middle response let them identify middle stimuli. Concurrent memory tasks were occasionally overlain on ongoing discrimination performance. The concurrent tasks disrupted macaques' uncertainty responses far more than their sparse, middle, or dense discrimination responses. This dissociation suggests that the uncertainty response is a higher level decisional response that is particularly dependent on working memory and attentional resources. This is consistent with the theoretical possibility that the uncertainty response is an elemental behavioral index of uncertainty monitoring or metacognition.