Human personality generally refers to coherent individuating patterns in affect, behavior, and cognition. We can only observe and measure behavior, from which we then infer personality and other psychological processes (affect, cognition, etc.). We emphasize that the study of personality always explains or summarizes patterns not only in behavior but also in these other psychological processes inferred from behavior. We thus argue that personality should be attributed only to nonhuman animals with behaviors from which we can infer a sufficiently rich set of psychological processes. The mere inference of a biological trait that explains behavioral variability, on our view, is not sufficient to count as a personality construct and should be given a different term. Methodologically, inferring personality in nonhuman animals entails challenges in characterizing ecologically valid behaviors, doing so across rich and varied environments, and collecting enough data. We suggest that studies should gradually accumulate such corpora of data on a species through well-curated shared databases. A mixture of approaches should include both top-down fit with extant human personality theories (such as the Big Five) as well as bottom-up discovery of species-specific personality dimensions. Adopting the above framework will help us to build a comparative psychology and will provide the most informative models also for understanding human personality, its evolution, and its disorders.

The notion ‘quality of life’ (QoL) suggests that welfare in animals encompasses more than just an absence of suffering; it concerns the quality of an animal's entire relationship with its environment, of how it lives its life. Judgements of such quality are based on the integration of perceived details of how animals behave over time in different contexts. The scientific status of such judgements has long been ambiguous, but in recent decades has begun to be addressed by animal scientists. This paper starts with a brief review of qualitative approaches to the study of animal behaviour, which tend to address characteristics such as individuality, personality, and emotionality. The question then arises whether such characteristics involve a subjective, experiential aspect, and identify animals as sentient beings. The second half of this paper argues that taking the integrative nature of qualitative judgements seriously enables a ‘whole animal’ perspective, through which it becomes possible to view behaviour as a dynamic, expressive body language that provides a basis for assessing the quality of an animal's experience (eg contented, anxious). Judging this quality is a skill that requires knowledge of species-specific behaviour, experience in observing and interacting with animals in different contexts, and a willingness to communicate with animals as sentient beings. A substantial body of research indicates that this skill can function reliably in a scientific context, and can be applied usefully as a practical welfare assessment tool. Thus qualitative approaches to the study of animal behaviour should make an important contribution to the growing interest in animal QoL.

The effect of individual differences on the behaviour and reproduction of zoo animals has long been recognised by zoo biologists, yet only recently has the quantitative assessment of personality been used to investigate some of the challenges faced in zoo animal management. We review the findings of animal personality studies carried out in zoos since 1995. Our results reveal that zoo animal personality is most commonly assessed using observer ratings, where people who are familiar with the animals are asked to rate them on various personality traits. The reviewed studies indicate that zoo keepers are able to reliably rate animal personality traits, and these ratings are valid and related to behaviour. We identify promising areas of development in zoo animal personality research and suggest applications of personality profiling to zoo animal welfare and management. We argue that a validated personality questionnaire is a valuable tool for zoo professionals and advocate the implementation of personality assessment into existing zoo management practices to inform decisions on welfare and captive breeding.

Animal welfare is important for the humane treatment of animals under our care. Zoos and rescue centres manage various charismatic animals, such as big cats, with limited resources. It is therefore essential for caretakers to understand the needs of an individual big cat to ensure its welfare. However, these needs may differ due to a big cat's personality, which may be identified by its coping style in a stressful situation. In addition, stress is one of the major factors affecting animal welfare. There is limited evidence showing strong associations between personality and stress physiology in big cats. This review focuses on the integration of personality and stress physiology of captive big cats, to highlight possible improvements in their husbandry. Our review identifies key factors that may influence big cat responses to stressors. These influencing factors include: i) social interactions; ii) environment; iii) life history and evolutionary traits; iv) genetics; and v) health. The first two factors are relatively well covered in the literature; however, the final three are potentially very promising avenues for future research to better understand how we can improve big cat welfare.