Terminology use in animal personality research: a self-report questionnaire and a systematic review

Whether animal personality studies provide insights of broader evolutionary and ecological relevance to the field of behavioural ecology is frequently questioned. One of the sources of controversy is the vast, but often vague terminology present in the field. From a statistical perspective, animal personality is defined as among-individual variance in behaviour. However, numerous conceptual definitions of animal personality are available in the literature. Here, we performed (i) a self-report questionnaire and (ii) a systematic literature review to quantify how researchers interpreted conceptual and statistical definitions commonly used in animal personality research. We also compared whether data obtained from the questionnaire matched with data from the literature review. Among the 430 self-reported researchers that participated in our questionnaire, we observed discrepancies in key questions such as the conceptual definition of animal personality or the interpretation of repeatability. Furthermore, our literature review generally confirmed the global patterns revealed by the questionnaire. Overall, we identified common disagreements within the field of animal personality and discussed potential solutions. We advocate for adopting a terminology that avoids ambiguous interpretations and helps to make more explicit the widespread connotations implicit in the label 'animal personality'.