Potential resilience treatments for orangutans (Pongo spp.): Lessons from a scoping review of interventions in humans and other animals.

Wild orangutans (Pongo spp.) rescued from human-wildlife conflict must be adequately rehabilitated before being returned to the wild. It is essential that released orangutans are able to cope with stressful challenges such as food scarcity, navigating unfamiliar environments, and regaining independence from human support. Although practical skills are taught to orangutans in rehabilitation centres, post-release survival rates are low. Psychological resilience, or the ability to 'bounce back' from stress, may be a key missing piece of the puzzle. However, there is very little knowledge about species-appropriate interventions which could help captive orangutans increase resilience to stress. This scoping review summarises and critically analyses existing human and non-human animal resilience literature and provides suggestions for the development of interventions for orangutans in rehabilitation. Three scientific databases were searched in 2021 and 2023, resulting in 63 human studies and 266 non-human animal studies. The first section brings together human resilience interventions, identifying common themes and assessing the applicability of human interventions to orangutans in rehabilitation. The second section groups animal interventions into categories of direct stress, separation stress, environmental conditions, social stress, and exercise. In each category, interventions are critically analysed to evaluate their potential for orangutans in rehabilitation. The results show that mild and manageable forms of intervention have the greatest potential benefit with the least amount of risk. The study concludes by emphasising the need for further investigation and experimentation, to develop appropriate interventions and measure their effect on the post-release survival rate of orangutans.

The role of great ape behavioral ecology in One Health: Implications for captive welfare and re-habilitation success.

Behavior is the interface through which animals interact with their environments, and therefore has potentially cascading impacts on the health of individuals, populations, their habitats, and the humans that share them. Evolution has shaped the interaction between species and their environments. Thus, alterations to the species-typical "wild-type" behavioral repertoire (and the ability of the individual to adapt flexibly which elements of the repertoire it employs) may disrupt the relationship between the organism and its environment, creating cascading One Health effects. A good example is rehabilitant orangutans where, for example, seemingly minor differences from wild conspecifics in the time spent traveling on the ground rather than in the forest canopy can affect an individual's musculoskeletal and nutritional health, as well as social integration. It can also increase two-way transmission of infectious diseases and/or pathogens with local human populations, or potentially with neighboring wild populations if there are no geographical barriers and rehabilitants travel far enough to leave their release area. Primates are well known ecosystem engineers, reshaping plant communities and maintaining biodiversity through seed dispersal, consuming plants, and creating canopy gaps and trails. From the habitat perspective, a rehabilitant orangutan which does not behave like a wild orangutan is unlikely to fulfill these same ecosystem services. Despite the importance of the diversity of an ape's behavioral repertoire, how it compares to that of wild conspecifics and how it alters in response to habitat variation, behavior is an often under-appreciated aspect of One Health. In this review, focusing on orangutans as an example of the kinds of problems faced by all captive great apes, we examine the ways in which understanding and facilitating the expression of wild-type behavior can improve their health, their ability to thrive, and the robustness of local One Health systems.

Bird brains: Does absolute size matter?

Kabadayi, Taylor, von Bayern, and Osvath (2016, Royal Society Open Science, 3, 160104) recently showed that among birds, absolute brain size predicts performance on a motor self-control task thought to be important for cognition. However, birds performed at an equivalent level to much larger-brained primates, opening up the debate about brain size and cognition.

Development of planning in 4- to 10-year-old children: reducing inhibitory demands does not improve performance.

Currently, there are relatively few tasks suitable for testing planned problem solving in children. We presented 4- to 10-year-old children (N=172) with two planning tasks (sequential planning and advance planning) using the paddle-box apparatus, which was originally designed to investigate the planning skills of nonhuman apes. First, we were interested in the development of children's performance in the two tasks and whether the strategies children used to succeed differed among age groups. Performance improved significantly across age groups in both tasks. Strategies for success in the advance planning task differed among age groups, with 4- and 5-year-olds performing more excess actions, and a greater proportion of irrelevant excess actions, than older children. Findings are discussed in relation to the development of performance in tower tasks, which are a commonly used test of planning ability in humans. Second, based on previous findings with apes, we predicted that introducing measures to reduce the inhibitory demands of the advance planning task would improve children's performance. Therefore, in this study we introduced two methodological alterations that have been shown to improve children's performance in other tasks with inhibitory demands: (a) imposing a short delay before a child is allowed to act and (b) replacing reward items with symbolic tokens. Surprisingly, neither of these measures improved the performance of children in any of the age groups, suggesting that, contrary to our prediction, inhibitory control might not be a key performance-limiting factor in the advance planning paddle-box task.

The puzzling difficulty of tool innovation: why can't children piece their knowledge together?

Tool innovation-designing and making novel tools to solve tasks-is extremely difficult for young children. To discover why this might be, we highlighted different aspects of tool making to children aged 4 to 6 years (N=110). Older children successfully innovated the means to make a hook after seeing the pre-made target tool only if they had a chance to manipulate the materials during a warm-up. Older children who had not manipulated the materials and all younger children performed at floor. We conclude that children's difficulty is likely to be due to the ill-structured nature of tool innovation problems, in which components of a solution must be retrieved and coordinated. Older children struggled to bring to mind components of the solution but could coordinate them, whereas younger children could not coordinate components even when explicitly provided.

What cognitive strategies do orangutans (Pongo pygmaeus) use to solve a trial-unique puzzle-tube task incorporating multiple obstacles?

Apparently sophisticated behaviour during problem-solving is often the product of simple underlying mechanisms, such as associative learning or the use of procedural rules. These and other more parsimonious explanations need to be eliminated before higher-level cognitive processes such as causal reasoning or planning can be inferred. We presented three Bornean orangutans with 64 trial-unique configurations of a puzzle-tube to investigate whether they were able to consider multiple obstacles in two alternative paths, and subsequently choose the correct direction in which to move a reward in order to retrieve it. We were particularly interested in how subjects attempted to solve the task, namely which behavioural strategies they could have been using, as this is how we may begin to elucidate the cognitive mechanisms underpinning their choices. To explore this, we simulated performance outcomes across the 64 trials for various procedural rules and rule combinations that subjects may have been using based on the configuration of different obstacles. Two of the three subjects solved the task, suggesting that they were able to consider at least some of the obstacles in the puzzle-tube before executing action to retrieve the reward. This is impressive compared with the past performances of great apes on similar, arguably less complex tasks. Successful subjects may have been using a heuristic rule combination based on what they deemed to be the most relevant cue (the configuration of the puzzle-tube ends), which may be a cognitively economical strategy.

Tool innovation may be a critical limiting step for the establishment of a rich tool-using culture: a perspective from child development.

Recent data show that human children (up to 8 years old) perform poorly when required to innovate tools. Our tool-rich culture may be more reliant on social learning and more limited by domain-general constraints such as ill-structured problem solving than otherwise thought.

Vision, touch and object manipulation in Senegal parrots Poicephalus senegalus.

Parrots are exceptional among birds for their high levels of exploratory behaviour and manipulatory abilities. It has been argued that foraging method is the prime determinant of a bird's visual field configuration. However, here we argue that the topography of visual fields in parrots is related to their playful dexterity, unique anatomy and particularly the tactile information that is gained through their bill tip organ during object manipulation. We measured the visual fields of Senegal parrots Poicephalus senegalus using the ophthalmoscopic reflex technique and also report some preliminary observations on the bill tip organ in this species. We found that the visual fields of Senegal parrots are unlike those described hitherto in any other bird species, with both a relatively broad frontal binocular field and a near comprehensive field of view around the head. The behavioural implications are discussed and we consider how extractive foraging and object exploration, mediated in part by tactile cues from the bill, has led to the absence of visual coverage of the region below the bill in favour of more comprehensive visual coverage above the head.

Avian cognition: understanding tool use.

Although rooks are considered non-tool-using animals, a recent study has shown that they learn to solve a 'trap-tube' task faster than many tool-using primates, raising questions about the evolution of sophisticated physical cognition.

Boldness traits, not dominance, predict exploratory flight range and homing behaviour in homing pigeons.

Group living has been proposed to yield benefits that enhance fitness above the level that would be achieved through living as solitary individuals. Dominance hierarchies occur commonly in these social assemblages, and result, by definition, in resources not being evenly distributed between group members. Determinants of rank within a dominance hierarchy can be associated with morphological characteristics, previous experience of the individual, or personality traits such as exploration tendencies. The purpose of this study was to investigate whether greater exploration and positive responses to novel objects in homing pigeons (Columba livia) measured under laboratory conditions were associated with (i) greater initial exploration of the local area around the home loft during spontaneous exploration flights (SEF), (ii) faster and more efficient homing flights when released from further afield, and (iii) whether the traits of greater exploration and more positive responses to novel objects were more likely to be exhibited by the more dominant individuals within the group. There was no relationship between laboratory-based novel object exploration and position within the dominance hierarchy. Pigeons that were neophobic under laboratory conditions did not explore the local area during SEF opportunities. When released from sites further from home, neophobic pigeons took longer routes to home compared to those birds that had not exhibited neophobic traits under laboratory conditions, and had spontaneously explored to a greater extent. The lack of exploration in the neophobic birds is likely to have resulted in the increased costs of homing following release: unfamiliarity with the landscape likely led to the greater distances travelled and less efficient routes taken. Birds that demonstrated a lack of neophobia were not the dominant individuals inside the loft, and thus would have less access to resources such as food and potentially mates. However, a lack of neophobia makes the subordinate position possible, because subordinate birds that incur high travel costs would become calorie restricted and lose condition. Our results address emerging questions linking individual variation in behaviour with energetics and fitness consequences.This article is part of the themed issue 'Physiological determinants of social behaviour in animals'.

Individual differences in children's innovative problem-solving are not predicted by divergent thinking or executive functions.

Recent studies of children's tool innovation have revealed that there is variation in children's success in middle-childhood. In two individual differences studies, we sought to identify personal characteristics that might predict success on an innovation task. In Study 1, we found that although measures of divergent thinking were related to each other they did not predict innovation success. In Study 2, we measured executive functioning including: inhibition, working memory, attentional flexibility and ill-structured problem-solving. None of these measures predicted innovation, but, innovation was predicted by children's performance on a receptive vocabulary scale that may function as a proxy for general intelligence. We did not find evidence that children's innovation was predicted by specific personal characteristics.

The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii).

For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence. Orangutans have developed a diverse range of locomotor behaviour to cross gaps between trees, which vary in their physical and cognitive demands. The aims of this study were to examine the ontogeny of orangutan gap crossing behaviours and to determine which factors influence the distance orangutans crossed. A non-invasive photographic technique was used to quantify forearm length as a measure of body size. We also recorded locomotor behaviour, support use and the distance crossed between trees. Our results suggest that gap crossing varies with both physical and cognitive development. More complex locomotor behaviours, which utilized compliant trunks and lianas, were used to cross the largest gaps, but these peaked in frequency much earlier than expected, between the ages of 4 and 5 years old, which probably reflects play behaviour to perfect locomotor techniques. Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation. Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

Lateralization of tool use in New Caledonian crows (Corvus moneduloides).

We studied laterality of tool use in 10 captive New Caledonian (NC) crows (Corvus moneduloides). All subjects showed near-exclusive individual laterality, but there was no overall bias in either direction (five were left-lateralized and five were right-lateralized). This is consistent with results in non-human primates, which show strong individual lateralization for tool use (but not for other activities), and also with observations of four wild NC crows by Rutledge & Hunt. Jointly, these results contrast with observations that the crows have a population-level bias for manufacturing tools from the left edges of Pandanus sp. leaves, and suggest that the manufacture and use of tools in this species may have different neural underpinnings.

Is tool-making knowledge robust over time and across problems?

In three studies, we explored the retention and transfer of tool-making knowledge, learnt from an adult demonstration, to other temporal and task contexts. All studies used a variation of a task in which children had to make a hook tool to retrieve a bucket from a tall transparent tube. Children who failed to innovate the hook tool independently saw a demonstration. In Study 1, we tested children aged 4-6 years (N = 53) who had seen the original demonstration 3 months earlier. Performance was excellent at the second time, indicating that children's knowledge was retained over the 3 month period. In Studies 2 and 3 we explored transfer of the new knowledge to other tasks. In Study 2, children were given two variants of the apparatus that differed in surface characteristics (e.g., shape and color). Participants generalized their knowledge to these new apparatuses even though the new pipecleaner also differed in size and color. Five- to 6-year-olds (N = 22) almost always transferred their knowledge to problems where the same tool had to be made. Younger, 3- to 5-year-olds' (N = 46), performance was more variable. In Study 3, 4- to 7-year-olds (N = 146) saw a demonstration of hook making with a pipecleaner, but then had to make a tool by combining pieces of wooden dowel (or vice versa: original training on dowel, transfer to pipecleaner). Children did not transfer their tool-making knowledge to the new material. Children retained tool-making knowledge over time and transferred their knowledge to new situations in which they needed to make a similar tool from similar materials, but not different materials. We concluded that children's ability to use tool-making knowledge in novel situations is likely to depend on memory and analogical reasoning, with the latter continuing to develop during middle childhood.

A novel test of planning ability: great apes can plan step-by-step but not in advance of action.

The ability to identify an appropriate sequence of actions or to consider alternative possible action sequences might be particularly useful during problem solving in the physical domain. We developed a new 'paddle-box' task to test the ability of different ape species to plan an appropriate sequence of physical actions (rotating paddles) to retrieve a reward from a goal location. The task had an adjustable difficulty level and was not dependent on species-specific behaviours (e.g. complex tool use). We investigated the planning abilities of captive orangutans (Pongo pygmaeus) and bonobos (Pan paniscus) using the paddle-box. In experiment 1, subjects had to rotate one or two paddles before rotating the paddle with the reward on. Subjects of both species performed poorly, though orangutans rotated more non-food paddles, which may be related to their greater exploratory tendencies and bolder temperament compared with bonobos. In experiment 2 subjects could always rotate the paddle with the reward on first and still succeed, and most subjects of both species performed appropriate sequences of up to three paddle rotations to retrieve the reward. Poor performance in experiment 1 may have been related to subjects' difficulty in inhibiting the prepotent response to act on the reward immediately.

The development of tool manufacture in humans: what helps young children make innovative tools?

We know that even young children are proficient tool users, but until recently, little was known about how they make tools. Here, we will explore the concepts underlying tool making, and the kinds of information and putative cognitive abilities required for children to manufacture novel tools. We will review the evidence for novel tool manufacture from the comparative literature and present a growing body of data from children suggesting that innovation of the solution to a problem by making a tool is a much more challenging task than previously thought. Children's difficulty with these kinds of tasks does not seem to be explained by perseveration with unmodified tools, difficulty with switching to alternative strategies, task pragmatics or issues with permission. Rather, making novel tools (without having seen an example of the required tool within the context of the task) appears to be hard, because it is an example of an 'ill-structured problem'. In this type of ill-structured problem, the starting conditions and end goal are known, but the transformations and/or actions required to get from one to the other are not specified. We will discuss the implications of these findings for understanding the development of problem-solving in humans and other animals.

Biological and artificial cognition: what can we learn about mechanisms by modelling physical cognition problems using artificial intelligence planning techniques?

Do we fully understand the structure of the problems we present to our subjects in experiments on animal cognition, and the information required to solve them? While we currently have a good understanding of the behavioural and neurobiological mechanisms underlying associative learning processes, we understand much less about the mechanisms underlying more complex forms of cognition in animals. In this study, we present a proposal for a new way of thinking about animal cognition experiments. We describe a process in which a physical cognition task domain can be decomposed into its component parts, and models constructed to represent both the causal events of the domain and the information available to the agent. We then implement a simple set of models, using the planning language MAPL within the MAPSIM simulation environment, and applying it to a puzzle tube task previously presented to orangutans. We discuss the results of the models and compare them with the results from the experiments with orangutans, describing the advantages of this approach, and the ways in which it could be extended.

How to build an information gathering and processing system: lessons from naturally and artificially intelligent systems.

Imagine a situation in which you had to design a physical agent that could collect information from its environment, then store and process that information to help it respond appropriately to novel situations. What kinds of information should it attend to? How should the information be represented so as to allow efficient use and re-use? What kinds of constraints and trade-offs would there be? There are no unique answers. In this paper, we discuss some of the ways in which the need to be able to address problems of varying kinds and complexity can be met by different information processing systems. We also discuss different ways in which relevant information can be obtained, and how different kinds of information can be processed and used, by both biological organisms and artificial agents. We analyse several constraints and design features, and show how they relate both to biological organisms, and to lessons that can be learned from building artificial systems. Our standpoint overlaps with Karmiloff-Smith (1992) in that we assume that a collection of mechanisms geared to learning and developing in biological environments are available in forms that constrain, but do not determine, what can or will be learnt by individuals.

Extreme binocular vision and a straight bill facilitate tool use in New Caledonian crows.

Humans are expert tool users, who manipulate objects with dextrous hands and precise visual control. Surprisingly, morphological predispositions, or adaptations, for tool use have rarely been examined in non-human animals. New Caledonian crows Corvus moneduloides use their bills to craft complex tools from sticks, leaves and other materials, before inserting them into deadwood or vegetation to extract prey. Here we show that tool use in these birds is facilitated by an unusual visual-field topography and bill shape. Their visual field has substantially greater binocular overlap than that of any other bird species investigated to date, including six non-tool-using corvids. Furthermore, their unusually straight bill enables a stable grip on tools, and raises the tool tip into their visual field's binocular sector. These features enable a degree of tool control that would be impossible in other corvids, despite their comparable cognitive abilities. To our knowledge, this is the first evidence for tool-use-related morphological features outside the hominin lineage.

Making tools isn't child's play.

Tool making evidences intelligent, flexible thinking. In Experiment 1, we confirmed that 4- to 7-year-olds chose a hook tool to retrieve a bucket from a tube. In Experiment 2, 3- to 5-year-olds consistently failed to innovate a simple hook tool. Eight-year-olds performed at mature levels. In contrast, making a tool following demonstration was easy for even the youngest children. In Experiment 3, children's performance did not improve given the opportunity to manipulate the objects in a warm-up phase. Children's tool innovation lags substantially behind their ability to learn how to make tools by observing others.