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In the past decade, several conceptual papers have linked variation in animal personality to variation in cognition, and recent years have seen a flood of empirical studies testing this link. However, these results have not been synthesized in a quantitative way. Here, we systematically search the literature and conduct a phylogenetically controlled meta-analysis of empirical papers that have tested the relationship between animal personality (exploration, boldness, activity, aggression and sociability) and cognition (initial learning/reversal speed, number of correct choices/errors after standard training). We find evidence for a small but significant relationship between variation in personality and variation in learning across species in the absolute scale; however, the of this relationship is highly variable and when both positive and negative effect sizes are considered, the average effect size does not differ significantly from zero. Importantly, this variation among studies is not explained by differences in personality or learning measure, or taxonomic grouping. Further, these results do not support current hypotheses suggesting that that fast-explorers are fast-learners or that slow-explorers perform better on tests of reversal learning. Rather, we find evidence that bold animals are faster learners, but only when boldness is measured in response to a predator (or simulated predator) and not when boldness is measured by exposure to a novel object (or novel food). Further, although only a small sub-sample of papers reported results separately for males and females, sex explained a significant amount of variation in effect size. These results, therefore, suggest that, while personality and learning are indeed related across a range of species, the direction of this relationship is highly variable. Thus further empirical work is needed to determine whether there are important moderators of this relationship.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

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Animal personality, defined as consistent individual differences across context and time, has attracted much recent research interest in the study of animal behaviour. More recently, this field has begun to examine how such variation arose and is maintained within populations. The habitat-dependent selection hypothesis, which posits that animals with differing personality types may fare better (i.e. have a fitness advantage) in different habitats, suggests one possible mechanism. In the current experiment, we tested whether slow-and fast-exploring black-capped chickadees (Poecile atricapillus), determined by performance in a novel environment exploration task, perform differentially when the demands of an acoustic operant discrimination (cognitive) task were altered following successful task acquisition. We found that slow-exploring birds learn to reverse previously learned natural category rules more quickly than faster exploring conspecifics. In accordance with the habitat-dependent selection hypothesis, and previous work with great tits (Parus major), a close relative of the black-capped chickadee, our results suggest that fast-exploring birds may perform better in stable, predictable environments where forming a routine is advantageous, while slow-exploring birds are favoured in unstable, unpredictable environments, where task demands often change. Our results also support a hypothesis derived from previous work with great tits; slow-exploring birds may be generally more flexible (i.e. able to modify their behaviour in accordance with changes in environmental stimuli) in some learning tasks.

Cognitive processes are important to animals because they not only influence how animals acquire, store and recall information, but also may underpin behaviours such as deciding where to look for food, build a nest, or with whom to mate. Several recent studies have begun to examine the potential interaction between variation in cognition and variation in personality traits. One hypothesis proposed that there is a speed-accuracy trade-off in cognition ability that aligns with a fast-slow behaviour type. Here, we explicitly examined this hypothesis by testing wild-caught black-capped chickadees in a series of cognitive tasks that assessed both learning speed (the number of trials taken to learn) and accuracy (post-acquisition performance when tested with un-trained exemplars). Chickadees' exploration scores were measured in a novel environment task. We found that slow-exploring chickadees demonstrated higher accuracy during the test phase, but did not learn the initial task in fewer trials compared to fast-exploring chickadees, providing partial support for the proposed link between cognition and personality. We report positive correlations in learning speed between different phases within cognitive tasks, but not between the three cognitive tasks suggesting independence in underlying cognitive processing. We discuss different rule-based strategies that may contribute to differential performance accuracy in cognitive tasks and provide suggestions for future experimentation to examine mechanisms underlying the relationship between cognition and personality.