Comparative psychometrics: establishing what differs is central to understanding what evolves

Cognitive abilities cannot be measured directly. What we can measure is individual variation in task performance. In this paper, we first make the case for why we should be interested in mapping individual differences in task performance on to particular cognitive abilities: we suggest that it is crucial for examining the causes and consequences of variation both within and between species. As a case study, we examine whether multiple measures of inhibitory control for non-human animals do indeed produce correlated task performance; however, no clear pattern emerges that would support the notion of a common cognitive ability underpinning individual differences in performance. We advocate a psychometric approach involving a three-step programme to make theoretical and empirical progress: first, we need tasks that reveal signature limits in performance. Second, we need to assess the reliability of individual differences in task performance. Third, multi-trait multi-method test batteries will be instrumental in validating cognitive abilities. Together, these steps will help us to establish what varies between individuals that could impact their fitness and ultimately shape the course of the evolution of animal minds. Finally, we propose executive functions, including working memory, inhibitory control and attentional shifting, as a sensible starting point for this endeavour

Future thinking : children but not apes consider multiple possibilities

When anticipating the future, we draw on our past experience but must take uncertainty into account; for example, while preparing for a trip, we might pack a raincoat and sunglasses because of unpredictable weather. New research shows that the ability to plan for multiple future possibilities may be present in human children from as early as 3–4 years of age, but appears to be lacking in non-human apes.PostprintPeer reviewe

Inferring unseen causes : developmental and evolutionary origins

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 639072).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 nonhuman 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.Publisher PDFPeer reviewe

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

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 639072). Edinburgh Zoo's Living Links Research Facility is core supported by the Royal Zoological Society of Scotland (registered charity no.: SC004064) through funding generated by its visitors, members and supporters.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.Publisher PDFPeer reviewe

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

We are grateful to the Royal Zoological Society of Scotland (RZSS) and the University of St Andrews for core financial support to the RZSS Edinburgh Zoo’s Living Links Research Facility where this project was carried out.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.Publisher PDFPeer reviewe

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

This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement 639072). Brandon Tinklenberg was supported by a grant from the Social Sciences and Humanities Research Council of Canada (SSHRC 435-2016-1051).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.PostprintPeer reviewe

Knowing without knowing : implicit cognition and the minds of infants and animals

The main aim of this paper is to highlight the need to address the conceptual problem of “implicit knowledge” or “implicit cognition” —a notion especially important in the study of the nonverbal minds of animals and infants. We review some uses of the term ‘implicit’ in psychology and allied disciplines,and conclude that conceptual clarification of this notion is not only lacking, but largely avoided and reduced to a methodological problem. We propose that this elusive notion is central in the study not only of animal and infant minds, but also the human adult mind. Some promising approaches in developmental and evolutionary psychology towards innovative conceptualisation of implicit knowledge remain conceptually underdeveloped and in need of reconsideration and re-elaboration. We conclude by suggesting that the challenge of implicit cognition and nonverbal minds will only be solved through a concerted interdisciplinary approach between psychology and other disciplines.Publisher PDFPeer reviewe

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

Authors are grateful to the Royal Zoological Society of Scotland (RZSS) and the University of St Andrews for core financial support to the RZSS Edinburgh Zoo’s Living Links Research Centre, where this project was carried out. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. [639072]). We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) [funding reference number 2016-05552].Abstract 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.Publisher PDFPeer reviewe

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

Capuchin monkeys individuate objects based on spatio-temporal and property/kind information : evidence from looking and reaching measures

This paper is an output of the project ‘Rethinking Mind and Meaning: A case study from a co-disciplinary approach’ (Award Nr.: AH/ L015234/1), funded by the Arts and Humanities Research Council (AHRC), as part of the Science in Culture Theme (http://www.sciculture.ac.uk).A core component of any folk physical understanding of the world is object individuation - the cognitive ability to parse sensory input into discrete objects. Whereas younger human infants use spatio-temporal information to individuate objects, they do not use property and kind information until one year of age. Some researchers propose that object individuation based on property/kind information depends on language acquisition and sortal concepts. However, there is evidence that preverbal infants and nonhuman animals also use both types of information. The present study aimed to further explore the evolutionary origins of object individuation by testing a new-world monkey species, capuchin monkeys (Sapajus spp.), using both manual search (n = 29) and looking time (n = 23) measures. In Spatio-temporal trials, subjects saw one or two objects dropped into a box, but always found (or saw) only one. In Property/kind trials, subjects saw either object A or B being dropped into a box and then always found (or saw) object A. The capuchin monkeys looked longer and searched more on inconsistent trials – with outcome differing in quantity or in kind - which suggested that they had expectations based on both spatio-temporal and property-kind representations. Looking time and search measures gave convergent results at the group but not at the individual level. Our results add to the existing evidence contradicting the linguistic hypothesis of property/kind individuation. However, contrary to recent discussions, we argue that these and related results can be explained without appealing to the notion of sortal concepts or multiple representational systems, and suggest that a full picture of the ontogeny and phylogeny of object individuation requires further empirical and theoretical research.Publisher PDFPeer reviewe