Evidence for abstract representations in children but not capuchin monkeys.

The use of abstract higher-level knowledge (also called overhypotheses) allows humans to learn quickly from sparse data and make predictions in new situations. Previous research has suggested that humans may be the only species capable of abstract knowledge formation, but this remains controversial. There is also mixed evidence for when this ability emerges over human development. Kemp et al. (2007) proposed a computational model of how overhypotheses could be learned from sparse examples. We provide the first direct test of this model: an ecologically valid paradigm for testing two species, capuchin monkeys (Sapajus spp.) and 4- to 5-year-old human children. We presented participants with sampled evidence from different containers which suggested that all containers held items of uniform type (type condition) or of uniform size (size condition). Subsequently, we presented two new test containers and an example item from each: a small, high-valued item and a large but low-valued item. Participants could then choose from which test container they would like to receive the next sample - the optimal choice was the container that yielded a large item in the size condition or a high-valued item in the type condition. We compared performance to a priori predictions made by models with and without the capacity to learn overhypotheses. Children's choices were consistent with the model predictions and thus suggest an ability for abstract knowledge formation in the preschool years, whereas monkeys performed at chance level.

Do they know or just do it? Investigating implicit and explicit sequence learning by capuchin monkeys, human adults and children.

In humans, it is now established that sequential regularities can be learned implicitly (i.e. without acquiring conscious knowledge) or explicitly (with acquisition of conscious knowledge). Is this dual-processing capability also the case for non-human primates? In this study, we designed a non-verbal task to probe implicit and explicit sequence learning in capuchin monkeys (Sapajus sp., n = 12), human adults (n = 12), and children from 5 to 10 years old (n = 64). After learning spatial sequences on a touchscreen, participants' conscious access to the sequences was probed with a forced choice sequence completion test. All performed above chance level in this test, without being instructed or trained to do so. However, only human adults who reported the presence of regularities performed at ceiling level. We suggest future directions that could build on our findings to disentangle implicit and explicit learning in monkeys and children.

What happened? Do preschool children and capuchin monkeys spontaneously use visual traces to locate a reward?

The ability to infer unseen causes from evidence is argued to emerge early in development and to be uniquely human. We explored whether preschoolers and capuchin monkeys could locate a reward based on the physical traces left following a hidden event. Preschoolers and capuchin monkeys were presented with two cups covered with foil. Behind a barrier, an experimenter (E) punctured the foil coverings one at a time, revealing the cups with one cover broken after the first event and both covers broken after the second. One event involved hiding a reward, the other event was performed with a stick (order counterbalanced). Preschoolers and, with additional experience, monkeys could connect the traces to the objects used in the puncturing events to find the reward. Reversing the order of events perturbed the performance of 3-year olds and capuchins, while 4-year-old children performed above chance when the order of events was reversed from the first trial. Capuchins performed significantly better on the ripped foil task than they did on an arbitrary test in which the covers were not ripped but rather replaced with a differently patterned cover. We conclude that by 4 years of age children spontaneously reason backwards from evidence to deduce its cause.

Do capuchin monkeys (Sapajus apella) use exploration to form intuitions about physical properties?

Humans' flexible innovation relies on our capacity to accurately predict objects' behaviour. These predictions may originate from a "physics-engine" in the brain which simulates our environment. To explore the evolutionary origins of intuitive physics, we investigate whether capuchin monkeys' object exploration supports learning. Two capuchin groups experienced exploration sessions involving multiple copies of two objects, one object was easily opened (functional), the other was not (non-functional). We used two within-subject conditions (enrichment-then-test, and test-only) with two object sets per group. Monkeys then underwent individual test sessions where the objects contained rewards, and they choose one to attempt to open. The monkeys spontaneously explored, performing actions which yielded functional information. At test, both groups chose functional objects above chance. While high performance of the test-only group precluded us from establishing learning during exploration, this study reveals the promise of harnessing primates' natural exploratory tendencies to understand how they see the world.

Better all by myself: Gaining personal experience, not watching others, improves 3-year-olds' performance in a causal trap task.

Children often learn from others' demonstrations, but in the causal domain evidence acquired from observing others may be more ambiguous than evidence generated for oneself. Prior work involving tool-using tasks suggests that observational learning might not provide sufficient information about the causal relations involved, but it remains unclear whether these limitations can be mitigated by providing demonstrations using familiar manual actions rather than unfamiliar tools. We provided 2.5- to 3.5-year-old children (N = 67) with the opportunity to acquire experience with a causal trap task by hand or by tool actively or from observing others. Initially, children either generated their own experience or watched a yoked demonstration; all children then attempted the trap task with the tool. Children who generated their own experience outperformed those who watched the demonstration. Hand or tool use had no effect on performance with a tool. The implications of these findings for scaffolding self-guided learning and for demonstrations involving errors are discussed.

Chimpanzees flexibly update working memory contents and show susceptibility to distraction in the self-ordered search task.

Working memory (WM) is a core executive function that allows individuals to hold, process and manipulate information. WM capacity has been repeatedly nominated as a key factor in human cognitive evolution; nevertheless, little is known about the WM abilities of our closest primate relatives. In this study, we examined signatures of WM ability in chimpanzees (Pan troglodytes). Standard WM tasks for humans (Homo sapiens) often require participants to continuously update their WM. In Experiment 1, we implemented this updating requirement in a foraging situation: zoo-housed chimpanzees (n = 13) searched for food in an array of containers. To avoid redundant searches, they needed to continuously update which containers they had already visited (similar to WM paradigms for human children) with 15 s retention intervals in between each choice. We examined chimpanzees' WM capacity and to what extent they used spatial cues and object features to memorize their previous choices. In Experiment 2, we investigated how susceptible their WM was to attentional interference, an important signature, setting WM in humans apart from long-term memory. We found large individual differences with some individuals remembering at least their last four choices. Chimpanzees used a combination of spatial cues and object features to remember which boxes they had chosen already. Moreover, their performance decreased specifically when competing memory information was introduced. Finally, we found that individual differences in task performance were highly reliable over time. Together, these findings show remarkable similarities between human and chimpanzee WM abilities despite evolutionary and life-history differences.

Diffusion of novel foraging behaviour in Amazon parrots through social learning.

While social learning has been demonstrated in species across many taxa, the role it plays in everyday foraging decisions is not well understood. Investigating social learning during foraging could shed light on the emergence of cultural variation in different groups. We used an open diffusion experiment to examine the spread of a novel foraging technique in captive Amazon parrots. Three groups were tested using a two-action foraging box, including experimental groups exposed to demonstrators using different techniques and control birds. We also examined the influence of agonistic and pilfering behaviour on task acquisition. We found evidence of social learning: more experimental birds than control birds interacted with and opened the box. The birds were, however, no more likely to use the demonstrated technique than the non-demonstrated one, making local or stimulus enhancement the most likely mechanism. Exhibiting aggression was positively correlated with box opening, whilst receiving aggression did not reduce motivation to engage with the box, indicating that willingness to defend access to the box was important in task acquisition. Pilfering food and success in opening the box were also positively correlated; however, having food pilfered did not affect victims' motivation to interact with the box. In a group context, pilfering may promote learning of new foraging opportunities. Although previous studies have demonstrated that psittacines are capable of imitation, in this naturalistic set-up there was no evidence that parrots copied the demonstrated opening technique. Foraging behaviour in wild populations of Amazons could therefore be facilitated by low-fidelity social learning mechanisms.

The evolution of self-control.

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

A novel form of spontaneous tool use displayed by several captive greater vasa parrots (Coracopsis vasa).

Parrots are frequently cited for their sophisticated problem-solving abilities, but cases of habitual tool use among psittacines are scarce. We report the first evidence, to our knowledge, of tool use by greater vasa parrots (Coracopsis vasa). Several members of a captive population spontaneously adopted a novel tool-using technique by using pebbles and date pits either (i) to scrape on the inner surface of seashells, subsequently licking the resulting calcium powder from the tool, or (ii) as a wedge to break off smaller pieces of the shell for ingestion. Tool use occurred most frequently just prior to the breeding season, during which time numerous instances of tool transfer were also documented. These observations provide new insights into the tool-using capabilities of parrots and highlight the greater vasa parrot as a species of interest for studies of physical cognition.

How can I find what I want? Can children, chimpanzees and capuchin monkeys form abstract representations to guide their behavior in a sampling task?

concepts are a powerful tool for making wide-ranging predictions in new situations based on little experience. Whereas looking-time studies suggest an early emergence of this ability in human infancy, other paradigms like the relational match to sample task often fail to detect abstract concepts until late preschool years. Similarly, non-human animals show difficulties and often succeed only after long training regimes. Given the considerable influence of slight task modifications, the conclusiveness of these findings for the development and phylogenetic distribution of abstract reasoning is debated. Here, we tested the abilities of 3 to 5-year-old children, chimpanzees, and capuchin monkeys in a unified and more ecologically valid task design based on the concept of "overhypotheses" (Goodman, 1955). Participants sampled high- and low-valued items from containers that either each offered items of uniform value or a mix of high- and low-valued items. In a test situation, participants should switch away earlier from a container offering low-valued items when they learned that, in general, items within a container are of the same type, but should stay longer if they formed the overhypothesis that containers bear a mix of types. We compared each species' performance to the predictions of a probabilistic hierarchical Bayesian model forming overhypotheses at a first and second level of abstraction, adapted to each species' reward preferences. Children and, to a more limited extent, chimpanzees demonstrated their sensitivity to abstract patterns in the evidence. In contrast, capuchin monkeys did not exhibit conclusive evidence for the ability of abstract knowledge formation.

How does cognition evolve? Phylogenetic comparative psychology.

Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologists have generated quantitative approaches to investigate the phylogenetic distribution and function of phenotypic traits, including cognition. In particular, phylogenetic methods can quantitatively (1) test whether specific cognitive abilities are correlated with life history (e.g., lifespan), morphology (e.g., brain size), or socio-ecological variables (e.g., social system), (2) measure how strongly phylogenetic relatedness predicts the distribution of cognitive skills across species, and (3) estimate the ancestral state of a given cognitive trait using measures of cognitive performance from extant species. Phylogenetic methods can also be used to guide the selection of species comparisons that offer the strongest tests of a priori predictions of cognitive evolutionary hypotheses (i.e., phylogenetic targeting). Here, we explain how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution.

Inhibitory control and cue relevance modulate chimpanzees' (Pan troglodytes) performance in a spatial foraging task.

Inhibition tasks usually require subjects to exert control to act correctly when a competing action plan is prepotent. In comparative psychology, one concern about the existing inhibition tasks is that the relative contribution of inhibitory control to performance (as compared to learning or object knowledge) is rarely explicitly investigated. We addressed this problem by presenting chimpanzees with a spatial foraging task in which they could acquire food more efficiently by learning which objects were baited. In Experiment 1, we examined how objects that elicited a prepotent approach response, transparent cups containing food, affected their learning rates. Although showing an initial bias to approach these sealed cups with visible food, the chimpanzees learned to avoid them more quickly across sessions compared to a color discrimination. They also learned a color discrimination more quickly if the incorrect cups were sealed such that a piece of food could never be hidden inside them. In Experiment 2, visible food of 2 different types was sealed in the upper part of the cups: 1 type signaled the presence of food reward hidden underneath; the cups with the other type were sealed. The chimpanzees learned more quickly in a congruent condition (the to-be-chosen food cue matched the reward) than in an incongruent condition (the to-be-avoided food cue matched the reward). Together, these findings highlight that performance in inhibition tasks is affected by several other cognitive abilities such as object knowledge, memory, and learning, which need to be quantified before meaningful comparisons can be drawn. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The structure of executive functions in preschool children and chimpanzees.

Executive functions (EF) are a core aspect of cognition. Research with adult humans has produced evidence for unity and diversity in the structure of EF. Studies with preschoolers favour a 1-factor model, in which variation in EF tasks is best explained by a single underlying trait on which all EF tasks load. How EF are structured in nonhuman primates remains unknown. This study starts to fill this gap through a comparative, multi-trait multi-method test battery with preschoolers (N = 185) and chimpanzees (N = 55). The battery aimed at measuring working memory updating, inhibition, and attention shifting with three non-verbal tasks per function. For both species the correlations between tasks were low to moderate and not confined to tasks within the same putative function. Factor analyses produced some evidence for the unity of executive functions in both groups, in that our analyses revealed shared variance. However, we could not conclusively distinguish between 1-, 2- or 3-factor models. We discuss the implications of our findings with respect to the ecological validity of current psychometric research.

Postconflict third-party affiliation in rooks, Corvus frugilegus.

Conflict features in the lives of many animal species and induces social stress mediated by glucocorticoid hormones [1]. Postconflict affiliation, between former opponents (reconciliation) or between former opponents and a bystander (third-party affiliation), has been suggested as a behavioral mechanism for reducing such stress [2], but has been studied almost exclusively in primates [3]. As with many primates, several bird species live in social groups and form affiliative relationships [4]. Do these distantly related animals also use affiliative behavior to offset the costs of conflict? We studied postconflict affiliation in a captive group of rooks. Unlike polygamous primates, monogamous rooks did not reconcile with former opponents. However, we found clear evidence of third-party affiliation after conflicts. Both initiators and targets of aggression engaged in third-party affiliation with a social partner and employed a specific behavior, bill twining, during the postconflict period. Both former aggressors and uninvolved third parties initiated affiliative contacts. Despite the long history of evolutionary divergence, the pattern of third-party affiliation in rooks is strikingly similar to that observed in tolerant primate species. Furthermore, the absence of reconciliation in rooks makes sense in light of the species differences in social systems.

Inferring Unseen Causes: Developmental and Evolutionary Origins.

Human adults can infer unseen causes because they represent the events around them in terms of their underlying causal mechanisms. It has been argued that young preschoolers can also make causal inferences from an early age, but whether or not non-human apes can go beyond associative learning when exploiting causality is controversial. However, much of the developmental research to date has focused on fully-perceivable causal relations or highlighted the existence of a causal relationship verbally and these were found to scaffold young children's abilities. We examined inferences about unseen causes in children and chimpanzees in the absence of linguistic cues. Children (N = 129, aged 3-6 years) and zoo-living chimpanzees (N = 11, aged 7-41 years) were presented with an event in which a reward was dropped through an opaque forked-tube into one of two cups. An auditory cue signaled which of the cups contained the reward. In the causal condition, the cue followed the dropping event, making it plausible that the sound was caused by the reward falling into the cup; and in the arbitrary condition, the cue preceded the dropping event, making the relation arbitrary. By 4-years of age, children performed better in the causal condition than the arbitrary one, suggesting that they engaged in reasoning. A follow-up experiment ruled out a simpler associative learning explanation. Chimpanzees and 3-year-olds performed at chance in both conditions. These groups' performance did not improve in a simplified version of the task involving shaken boxes; however, the use of causal language helped 3-year-olds. The failure of chimpanzees could reflect limitations in reasoning about unseen causes or a more general difficulty with auditory discrimination learning.

Investigating physical cognition in rooks, Corvus frugilegus.

Although animals (particularly tool-users) are capable of solving physical tasks in the laboratory , the degree to which they understand them in terms of their underlying physical forces is a matter of contention. Here, using a new paradigm, the two-trap tube task, we report the performance of non-tool-using rooks. In contrast to the low success rates of previous studies using trap-tube problems , seven out of eight rooks solved the initial task, and did so rapidly. Instead of the usual, conceptually flawed control, we used a series of novel transfer tasks to test for understanding. All seven transferred their solution across a change in stimuli. However, six out of seven were unable to transfer to two further tasks, which did not share any one visual constant. One female was able to solve these further transfer tasks. Her result is suggestive evidence that rooks are capable of sophisticated physical cognition, if not through an understanding of unobservable forces , perhaps through rule abstraction. Our results highlight the need to investigate cognitive mechanisms other than causal understanding in studying animal physical cognition.

Chimpanzees solve the trap problem when the confound of tool-use is removed.

The trap-tube problem is difficult for chimpanzees to solve; in several studies only 1 to 2 subjects learn the solution. The authors tested eight chimpanzees on a non-tool-using version of the problem to investigate whether the inclusion of a tool in previous tests of the trap problem may have masked the ability of chimpanzees to solve it. All eight learned to avoid the trap, in 40 to 100 trials. One transferred to two tasks that had no visual cue in common. The authors examined the performance of 15 chimpanzees on a new task in a 2 x 2 design: seven had experience on the two-trap box, eight had not; half of each group was tested with a tool, half without one. An ANOVA revealed a significant effect of tool-inclusion and experience (p < .05). Our results show that including a tool in the trap problem profoundly affects the ability of chimpanzees to solve it. With regard to what the chimpanzees had learned, the results support the notion that rather than using the available stimuli as arbitrary cues, the subjects had encoded information about functional properties.

Cooperation in children.

Cooperation is central to what makes us human. It is so deeply entrenched in our nature that it can be seen at the heart of every culture, whether it takes the form of group hunting, shared child-rearing, or large-scale, multi-national institutions such as the UN. And yet in contrast to the constancy of other forms of cooperation in non-human animals, such as termite-mound building or honey bee dancing, the changing face of human cooperation makes it seem more fragile, and its mechanisms more elusive. As with other features of our behaviour, human cooperation is the product of both genetic and cultural evolution. Studying cooperation in children, in different cultural environments, and in contrast to other species, provides a valuable window into the ways in which these two forms of inheritance interact over development, and a chance to distil out its constitutive components.