Neophobia is negatively related to reversal learning ability in females of a generalist bird of prey, the Chimango Caracara, Milvago chimango

Sex predicts response to novelty and problem-solving in a wild bird with female-biased sexual dimorphism

A wide range of animals, including a number of bird, fish, mammal and reptile species, show sex differences in cognitive tests. Hardly anything is known, however, about whether and how sex-specific non-cognitive factors (e.g. response to novelty) affect the expression of cognition in the wild. We used a series of learning and problem-solving tasks in wild breeding skuas, a species in which females are the larger sex (female-biased sexual size dimorphism). We also evaluated the birds' response to novelty (novel objects) before and after the tasks were administered. Both sexes performed equally well in learning (Discrimination-learning task) and re-learning (Reversal-learning task) food associations with colour and spatial cues, but female skuas outperformed males in problem-solving tasks (String-pulling task, Box-opening task). Females were also less neophobic than males: they were faster at accepting a food reward in novel situations. Better female performance may not imply higher cognition per se. Sex-specific size differences may translate into less or more neophobic behavioural types, which, in turn, predict females' problem-solving success and response to novelty. Species with female-biased sexual dimorphism may present a useful model to assess the interactions between sex, non-cognitive factors and cognition in the wild.

Background predation risk induces anxiety-like behaviour and predator neophobia in zebrafish

Prey face a major challenge in balancing predator avoidance with other essential activities. In environments with high risk, prey may exhibit neophobia (fear of novelty) due to the increased likelihood of novel stimuli being dangerous. The zebrafish, Danio rerio, is an established model organism for many scientific studies. Although spatial and object neophobia in zebrafish have received previous attention, little is known about the role of background risk in inducing neophobia in zebrafish. Here, we present two experiments using zebrafish to explore whether background predation risk can induce anxiety-like behaviour in a novel environment and neophobic responses when exposed to a novel odour. Over five days, we repeatedly exposed zebrafish to either high background risk in the form of chemical alarm cues (i.e., injured conspecific cues that indicate a predator attack) or a low-risk water control stimulus. In Experiment 1, when tested in a novel tank, zebrafish exposed to high predation risk displayed anxiety-like responses (reduced activity and increased bottom time spent) compared to their low-risk counterparts. Moreover, high-risk individuals showed reduced intra-session habituation to the novel tank compared to low-risk individuals. In Experiment 2, high-risk individuals exhibited fear responses toward a novel odour, unlike low-risk individuals. These results reveal that short-term repeated exposures to high risk can induce anxiety-like behaviour and predator odour neophobia in zebrafish.

Boldness affects novel object recognition in a gecko species

Individual animals exhibit considerable differences in cognitive characteristics associated with personality differences. The cognition-personality link was intensively investigated in the last decade though with mixed results. To grasp the general pattern, a common method should be applied to a wide range of animals. We tested novel object recognition (NOR) in the mourning gecko (Lepidodactylus lugubris) and investigated whether boldness, assessed in an anti-predator context, explained neophobia and how much attention animals pay to their surroundings. Boldness did not simply explain object neophobia but predicted attention to novel objects. Specifically, shy geckos showed shorter latency to approach the novel object than bold geckos only in the changed situation in which distinct types of objects were presented in two successive phases. However, no significant effect of boldness was detected in the unchanged situation in which the same object was presented twice. Our findings suggest that, in the mourning gecko, (1) boldness and object neophobia represent different aspects of personality traits and that (2) boldness underlies sensitivity to slight changes in the environment.

Are lateralized and bold fish optimistic or pessimistic?

Cognitive bias is defined as the influence of emotions on cognitive processes. The concept of the cognitive judgement bias has its origins in human psychology but has been applied to animals over the past 2 decades. In this study we were interested in determining if laterality and personality traits, which are known to influence learning style, might also be correlated with a cognitive bias in the three-spined sticklebacks (Gasterosteus aculeatus). We used the judgement bias test with the go/no-go procedure where fish were first trained to discriminate between a black and white card and, after reaching a minimum learning criterion, tested their response to an ambiguous card (grey). Optimistic subjects were expected to have a high expectation of reward associated with an ambiguous stimulus, whereas pessimistic subjects a high expectation of non-reward. We used an emergence and a mirror test to quantify boldness and laterality, respectively. We hypothesised that male, bolder and more strongly lateralized fish would be more optimistic than female, shy and less strongly lateralised fish. We found that males and more strongly lateralized fish were more optimistic than females and less strongly lateralized fish. In addition, bold males were more optimistic than shy males as we predicted, but females showed the opposite pattern. Finally, fish trained on the black colour card learned the training task faster than those trained on a white card. Our results indicate that both laterality and personality traits are linked to animals' internal states (pessimistic or optimistic outlooks) which likely has broad implications for understanding animal behaviour particularly in a welfare context.

Assessing sex differences in behavioural flexibility in an endangered bird species: the Southern ground-hornbill (Bucorvus leadbeateri)

Since ecology influences the expression of cognitive traits, intra-specific variation in ecological demands can drive differences in cognition. This is often the case, for instance, when sexes face different ecological challenges. However, so far, most studies have focused on few cognitive domains (i.e., spatial cognition), which limits our understanding of the evolution of sexually dimorphic cognition in animals. Endangered Southern ground-hornbills (Bucorvus leadbeateri), for example, show sex-specific ecological differences in age at dispersal, where females disperse from their natal group earlier than males. Based on this potential sex-specific source of selection, females and males may differ in their capacity to behave flexibly. Here, we used the reversal-learning paradigm in ten Southern ground-hornbills in two conditions: spatial and colour. During the pre-test (learning phase), regardless the sex, all subjects were faster at associating the food reward with spatial rather than with colour cues. Similarly, during the test (reversal-learning phase), both sexes learned the new association quicker with spatial cues. There were no sex differences in learning or reversal learning during both experimental phases. This possibility, however, requires further observation and experimentation. We hope our study will provide the impetus to assess further the cognitive capacities of this still overlooked species.

Fear of the new? Geckos hesitate to attack novel prey, feed near objects and enter a novel space

Neophobia, the fear of novelty, is an ecologically important response which enables animals to avoid potentially harmful situations. Neophobia is a cognitive process by which individuals distinguish novelty from familiarity. In this study, we aimed to quantify this cognitive process in captive tokay geckos (Gekko gecko) across three contexts: when encountering novel prey, foraging near novel objects and entering a novel space. We also investigated individual consistency across trials using different novel stimuli, and correlation of individual responses across the three contexts. We found that geckos hesitate to attack novel prey and prey close to objects (familiar and novel). Geckos hesitated the most when entering novel space. Repeatability of behaviour within and across contexts was low (R = 0.101-0.190) indicating that neophobia might not be expressed similarly across contexts. The strength of a neophobic response can indicate how anxious or curious an individual is. This test has great potential to help answer questions about how captivity, enrichment, rearing environment and cognition affect fear responses in different contexts in lizards. By studying reptiles, we can better understand the universality of what is known about the causes leading to difference in neophobia across individuals and species.

Bold and bright: shy and supple? The effect of habitat type on personality-cognition covariance in the Aegean wall lizard (Podarcis erhardii)

Animals exhibit considerable and consistent among-individual variation in cognitive abilities, even within a population. Recent studies have attempted to address this variation using insights from the field of animal personality. Generally, it is predicted that animals with "faster" personalities (bolder, explorative, and neophilic) should exhibit faster but less flexible learning. However, the empirical evidence for a link between cognitive style and personality is mixed. One possible reason for such conflicting results may be that personality-cognition covariance changes along ecological conditions, a hypothesis that has rarely been investigated so far. In this study, we tested the effect of habitat complexity on multiple aspects of animal personality and cognition, and how this influenced their relationship, in five populations of the Aegean wall lizard (Podarcis erhardii). Overall, lizards from both habitat types did not differ in average levels of personality or cognition, with the exception that lizards from more complex habitats performed better on a spatial learning task. Nevertheless, we found an intricate interplay between ecology, cognition, and personality, as behavioral associations were often habitat- but also year-dependent. In general, behavioral covariance was either independent of habitat, or found exclusively in the simple, open environments. Our results highlight that valuable insights may be gained by taking ecological variation into account while studying the link between personality and cognition.

Behavioural factors underlying innovative problem-solving differences in an avian predator from two contrasting habitats

Innovative behavior is considered one of the main factors facilitating the adaptation of animals to urban life. However, the relationship between urbanization and innovativeness is equivocal, perhaps reflecting aspects of urban environments that influence differently the behavioural traits underlying the occurrence of an innovation. In this work, we analysed the variation in innovative problem-solving performance between urban and rural individuals of the Caracara Chimango (Milvago chimango), with the goal of determining which behavioural trait (or combination) most explained such variation. We found that urban raptors outperformed rural ones in their solving speed and solving level (number of solutions) with a multiaccess box. They also showed more persistence, motor flexibility and diversity, as well as higher effectiveness in their solving attempts than rural chimangos. Sex was not an important factor. Urban chimangos showed less neophobia and spent more time exploring the box than rural birds during the initial habituation period, which probably determined the amount of information about the system that each individual had at the beginning of first problem solving trial. This difference in novelty response both directly and indirectly, through its relationship with persistence, motor flexibility and proportion of effective attempts, explained variability in solving performance. All individuals showed a decrease in solving latency, and an increase in solving level with experience, indicating that learning occurred in both raptor groups. This improvement occurred in parallel with changes in the afore-mentioned traits, though the pattern of improvement differed between urban and rural chimangos. We suggest that the characteristics of urban areas modulate the novelty response of chimangos, along with other correlated non-cognitive behavioural traits, which act in combination to increase the chances that novel problems could be quickly solved, and the resulting new behaviours established in city populations of this species.

Learning and motor inhibitory control in crows and domestic chickens

Cognitive abilities allow animals to navigate through complex, fluctuating environments. In the present study, we tested the performance of a captive group of eight crows, Corvus corone and 10 domestic chickens, Gallus gallus domesticus, in the cylinder task, as a test of motor inhibitory control and reversal learning as a measure of learning ability and behavioural flexibility. Four crows and nine chickens completed the cylinder task, eight crows and six chickens completed the reversal learning experiment. Crows performed better in the cylinder task compared with chickens. In the reversal learning experiment, species did not significantly differ in the number of trials until the learning criterion was reached. The performance in the reversal learning experiment did not correlate with performance in the cylinder task in chickens. Our results suggest crows to possess better motor inhibitory control compared with chickens. By contrast, learning performance in a reversal learning task did not differ between the species, indicating similar levels of behavioural flexibility. Interestingly, we describe notable individual differences in performance. We stress the importance not only to compare cognitive performance between species but also between individuals of the same species when investigating the evolution of cognitive skills.

Tracking Changes of Hidden Food: Spatial Pattern Learning in Two Macaw Species

Food availability may vary spatially and temporally within an environment. Efficiency in locating alternative food sources using spatial information (e.g., distribution patterns) may vary according to a species’ diet and habitat specialisation. Hypothetically, more generalist species would learn faster than more specialist species due to being more explorative when changes occur. We tested this hypothesis in two closely related macaw species, differing in their degree of diet and habitat specialisation; the more generalist Great Green Macaw and the more specialist Blue-throated Macaw. We examined their spatial pattern learning performance under predictable temporal and spatial change, using a ‘poke box’ that contained hidden food placed within wells. Each week, the rewarded wells formed two patterns (A and B), which were changed on a mid-week schedule. We found that the two patterns varied in their difficulty. We also found that the more generalist Great Green Macaws took fewer trials to learn the easier pattern and made more mean correct responses in the difficult pattern than the more specialist Blue-throated Macaws, thus supporting our hypothesis. The better learning performance of the Great Green Macaws may be explained by more exploration and trading-off accuracy for speed. These results suggest how variation in diet and habitat specialisation may relate to a species’ ability to adapt to spatial variation in food availability.

Sex differences in learning flexibility in an avian brood parasite, the shiny cowbird

Females of brood parasitic shiny cowbirds, Molothrus bonariensis, search and prospect host nests, synchronizing parasitism with host laying. This behavior is sex-specific, as females perform this task without male's assistance. Host nests must be removed from the female's memory "library" after being parasitized, to avoid repeated parasitism, or when they become unavailable because of predation. Thus, females must adjust their stored information about host nest status more dynamically than males, possibly leading to differences in learning flexibility. We tested for sex differences in a visual (local cues) and a spatial discrimination reversal learning task, expecting females to outperform males as an expression of greater behavioral flexibility. Both sexes learned faster the spatial than the visual task during both acquisition and reversal. In the visual task there were no sex differences in acquisition, but females reversed faster than males. In the spatial task there were no sex differences during either acquisition or reversal, possibly because of a ceiling effect: both sexes learned too fast for differences in performance to be detectable. Faster female reversal in a visual but not spatial task indicates that the greater behavioral flexibility in females may only be detectable above some level of task difficulty.

Dealing with the unexpected: the effect of environmental variability on behavioural flexibility in a Mediterranean lizard

Harsh and variable environments have been hypothesized to both drive and constrain the evolution towards higher cognitive abilities and behavioural flexibility. In this study, we compared the cognitive abilities of island and mainland Aegean wall lizards (Podarcis erhardii), which were expected to live in respectively a more variable and a more stable habitat. We used four proxies of behavioural flexibility: a neophobia assay, a problem-solving test and a spatial + reversal learning task. Surprisingly, the two populations did not differ in neophobia or problem-solving. Insular lizards, however, outperformed mainland conspecifics in an initial spatial learning task, but were less successful during the subsequent reversal learning. Our results thus seem to indicate that the effect of environmental variability on cognition is complex, as it may favour some, but not all aspects of behavioural flexibility.

Predictors of individual variation in reversal learning performance in three-spined sticklebacks

Behavioral flexibility is a type of phenotypic plasticity that can influence how animals cope with environmental change and is often measured with a reversal learning paradigm. The goal of this study was to understand why individuals differ in behavioral flexibility, and whether individual differences in behavioral flexibility fit the predictions of coping styles theory. We tested whether individual variation in flexibility correlates with response to novelty (response to a novel object), boldness (emergence into a novel environment), and behavioral persistence (response to a barrier), and tested for trade-offs between how quickly individuals learn an initial discrimination and flexibility. We compare results when reversal learning performance is measured during an early step of reversal learning (e.g. the number of errors during the first reversal session) to when reversal learning performance is measured by time to criterion. Individuals that made fewer mistakes during an early step of reversal learning spent more time away from the novel object, were less bold, less persistent, and performed worse during initial discrimination learning. In contrast, time to criterion was not correlated with any of the behaviors measured. This result highlights the utility of dissecting the steps of reversal learning to better understand variation in behavioral flexibility. Altogether, this study suggests that individuals differ in flexibility because flexibility is a key ingredient to their overall integrated strategy for coping with environmental challenges.

Heritability and correlations among learning and inhibitory control traits

To understand the evolution of cognitive abilities, we need to understand both how selection acts upon them and their genetic (co)variance structure. Recent work suggests that there are fitness consequences for free-living individuals with particular cognitive abilities. However, our current understanding of the heritability of these abilities is restricted to domesticated species subjected to artificial selection. We investigated genetic variance for, and genetic correlations among four cognitive abilities: inhibitory control, visual and spatial discrimination, and spatial ability, measured on >450 pheasants, Phasianus colchicus, over four generations. Pheasants were reared in captivity but bred from adults that lived in the wild and hence, were subject to selection on survival. Pheasant chicks are precocial and were reared without parents, enabling us to standardize environmental and parental care effects. We constructed a pedigree based on 15 microsatellite loci and implemented animal models to estimate heritability. We found moderate heritabilities for discrimination learning and inhibitory control (h2 = 0.17-0.23) but heritability for spatial ability was low (h2 = 0.09). Genetic correlations among-traits were largely positive but characterized by high uncertainty and were not statistically significant. Principle component analysis of the genetic correlation matrix estimate revealed a leading component that explained 69% of the variation, broadly in line with expectations under a general intelligence model of cognition. However, this pattern was not apparent in the phenotypic correlation structure which was more consistent with a modular view of animal cognition. Our findings highlight that the expression of cognitive traits is influenced by environmental factors which masks the underlying genetic structure.

Multiple factors affect discrimination learning performance, but not between-individual variation, in wild mixed-species flocks of birds

Cognition arguably drives most behaviours in animals, but whether and why individuals in the wild vary consistently in their cognitive performance is scarcely known, especially under mixed-species scenarios. One reason for this is that quantifying the relative importance of individual, contextual, ecological and social factors remains a major challenge. We examined how many of these factors, and sources of bias, affected participation and performance, in an initial discrimination learning experiment and two reversal learning experiments during self-administered trials in a population of great tits and blue tits. Individuals were randomly allocated to different rewarding feeders within an array. Participation was high and only weakly affected by age and species. In the initial learning experiment, great tits learned faster than blue tits. Great tits also showed greater consistency in performance across two reversal learning experiments. Individuals assigned to the feeders on the edge of the array learned faster. More errors were made on feeders neighbouring the rewarded feeder and on feeders that had been rewarded in the previous experiment. Our estimates of learning consistency were unaffected by multiple factors, suggesting that, even though there was some influence of these factors on performance, we obtained a robust measure of discrimination learning in the wild.

Modelling the evolution of cognitive styles

BACKGROUND

Individuals consistently differ in behaviour, exhibiting so-called personalities. In many species, individuals differ also in their cognitive abilities. When personalities and cognitive abilities occur in distinct combinations, they can be described as 'cognitive styles'. Both empirical and theoretical investigations produced contradicting or mixed results regarding the complex interplay between cognitive styles and environmental conditions.

RESULTS

Here we use individual-based simulations to show that, under just slightly different environmental conditions, different cognitive styles exist and under a variety of conditions, can also co-exist. Co-existences are based on individual specialization on different resources, or, more generally speaking, on individuals adopting different niches or microhabitats.

CONCLUSIONS

The results presented here suggest that in many species, individuals of the same population may adopt different cognitive styles. Thereby the present study may help to explain the variety of styles described in previous studies and why different, sometimes contradicting, results have been found under similar conditions.

The role of personality, cognition, and affective state in same-sex contests in the red junglefowl

Abstract

Intra-species contests are common in the animal kingdom and can have fitness consequences. Most research on what predicts contest outcome focuses on morphology, although differences in personality and cognition may also be involved. Supporting this, more proactive individuals often have dominant status, although the causality of this relationship is rarely investigated. Contest initiators often win; thus, individuals that are more proactive in their personality (e.g., more aggressive, risk-taking) or cognition (e.g., more optimistic, impulsive) may initiate contests more often. To investigate this, we assayed the behavior and cognition of sexually mature male and female red junglefowl (Gallus gallus), a species in which both sexes contest over social status, before staging intra-sexual contests. We confirm that contest initiators were more likely to win. In males, individuals that behaved more boldly in a novel arena test were more likely to initiate and win contests. Female initiators tended to be less active in novel object test, more aggressive in a restrained opponent test, and respond less optimistically in a cognitive judgement bias test, whereas the main predictor of whether a female would win a contest was whether she initiated it. These results suggest that behaviors attributed to proactive and reactive personalities, and—at least for female red junglefowl—optimism, can affect contest initiation and outcome. Therefore, within species, and depending on sex, different aspects of behavior and cognition may independently affect contest initiation and outcome. The generality of these findings, and their fitness consequences, requires further investigation.

Significance statement

In red junglefowl, we explored how behavior previously shown to describe personality, cognition, and affective state affected initiation and outcome of intra-sexual contests, by staging contests between sexually mature individuals previously assayed in behavioral and cognitive tests. In both sexes, contest initiators usually won. Bolder males were more likely to initiate and win contests. Female contests initiators were less active, more aggressive, and less optimistic. Our results suggest that personality and cognition could affect the initiation and outcome of contests and that how this occurs may differ between sexes.

Urban living predicts behavioural response in a neotropical raptor

Behaviour is expected to be one of the most important factors driving urban living of bird species because it largely determines how animals interact with their environments. The contribution of different behavioural traits as facilitators of contemporary process of bird colonization of urban environments, however, is still unclear. Here we examined the differences in three behavioural traits: neophobia (avoidance of a new object) and solving success and solving latency of a problem solving test related to obtain food, in rural and urban living individuals of a common diurnal Neotropical raptor, the chimango caracara (Phalcoboenus chimango). Moreover, for solving success and solving latency behaviours, we tested the plasticity (i.e., habituation) in birds. Urban and rural chimangos showed similar neophobia of a new object. All chimangos showed an improvement in their output in problem-solving test as the five-day testing passed but urban chimangos showed higher solving capabilities than rural conspecifics as they were more successful in solving the problem test. More, urban birds shown lower solving latency than rural, as they were able to improve their test performance by opening doors in less time as the day passed; in rural birds this relation was not so abrupt. In addition, those individuals that opened more doors, opened these faster too. Lastly, both solving success and latency showed very low individual consistency (repeatability < 0.275). Our results provide evidence of plasticity in solving capabilities of chimango caracaras which reveal that a habituation process in these behavioural traits could be associated to establishment of birds in urban environments.

Heritabilities and co-variation among cognitive traits in red junglefowl

Natural selection can act on between-individual variation in cognitive abilities, yet evolutionary responses depend on the presence of underlying genetic variation. It is, therefore, crucial to determine the relative extent of genetic versus environmental control of these among-individual differences in cognitive traits to understand their causes and evolutionary potential. We investigated heritability of associative learning performance and of a cognitive judgement bias (optimism), as well as their covariation, in a captive pedigree-bred population of red junglefowl (Gallus gallus, n > 300 chicks over 5 years). We analysed performance in discriminative and reversal learning (two facets of associative learning), and cognitive judgement bias, by conducting animal models to disentangle genetic from environmental contributions. We demonstrate moderate heritability for reversal learning, and weak to no heritability for optimism and discriminative learning, respectively. The two facets of associative learning were weakly negatively correlated, consistent with hypothesized trade-offs underpinning individual cognitive styles. Reversal, but not discriminative learning performance, was associated with judgement bias; less optimistic individuals reversed a previously learnt association faster. Together these results indicate that genetic and environmental contributions differ among traits. While modular models of cognitive abilities predict a lack of common genetic control for different cognitive traits, further investigation is required to fully ascertain the degree of covariation between a broader range of cognitive traits and the extent of any shared genetic control.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Are some individuals generally more behaviorally plastic than others? An experiment with sailfin mollies

Individuals within the same population generally differ among each other not only in their behavioral traits but also in their level of behavioral plasticity (i.e., in their propensity to modify their behavior in response to changing conditions). If the proximate factors underlying individual differences in behavioral plasticity were the same for any measure of plasticity, as commonly assumed, one would expect plasticity to be repeatable across behaviors and contexts. However, this assumption remains largely untested. Here, we conducted an experiment with sailfin mollies (Poecilia latipinna) whose behavioral plasticity was estimated both as the change in their personality traits or mating behavior across a social gradient and using their performance on a reversal-learning task. We found that the correlations between pairwise measures of plasticity were weak and non-significant, thus indicating that the most plastic individuals were not the same in all the tests. This finding might arise because either individuals adjust the magnitude of their behavioral responses depending on the benefits of plasticity, and/or individuals expressing high behavioral plasticity in one context are limited by neural and/or physiological constraints in the amount of plasticity they can express in other contexts. Because the repeatability of behavioral plasticity may have important evolutionary consequences, additional studies are needed to assess the importance of trade-offs between conflicting selection pressures on the maintenance of intra-individual variation in behavioral plasticity.

Cognition in the field: comparison of reversal learning performance in captive and wild passerines

Animal cognitive abilities have traditionally been studied in the lab, but studying cognition in nature could provide several benefits including reduced stress and reduced impact on life-history traits. However, it is not yet clear to what extent cognitive abilities can be properly measured in the wild. Here we present the first comparison of the cognitive performance of individuals from the same population, assessed using an identical test, but in contrasting contexts: in the wild vs. in controlled captive conditions. We show that free-ranging great tits (Parus major) perform similarly to deprived, captive birds in a successive spatial reversal-learning task using automated operant devices. In both captive and natural conditions, more than half of birds that contacted the device were able to perform at least one spatial reversal. Moreover, both captive and wild birds showed an improvement of performance over successive reversals, with very similar learning curves observed in both contexts for each reversal. Our results suggest that it is possible to study cognitive abilities of wild animals directly in their natural environment in much the same way that we study captive animals. Such methods open numerous possibilities to study and understand the evolution and ecology of cognition in natural populations.