Definition and interpretation effects: How different vigilance definitions can produce varied results

Abstract

Animals use vigilance to detect or monitor threats. While numerous aspects of vigilance have been studied across a wide range of species, little work has explored the methodological variation that has emerged across these studies. Different approaches in sampling designs, statistical analyses, and definitions can make cross-study comparisons challenging and potentially obscure our understanding of animal vigilance. In this study we explore two important components of vigilance definitions and ask: 1) whether definitions vary in their inter-observer agreement, and 2) whether using different definitions can create varied results within and across observers. Separate groups of ‘experienced’ and ‘inexperienced’ observers extracted data from video focal observations of wild chacma baboons, using four different definitions representative of the variation found within primate vigilance literature. In the first stage of analysis, we found that the four definitions varied in their inter-observer agreement, with only an operational looking definition performing well across both duration and frequency assessments, and an experienced/ inexperienced dichotomy. This suggests definitions vary in how well observers can converge on similar interpretations of the same definition. The second part of the analysis used the experienced group’s data in a typical primate vigilance analysis and found results varied within observers across definitions, i.e., definition effects, and across observers within definitions, i.e., interpretation effects. Together these results suggest that variation in definitions and their interpretation could have a fundamental role in producing between-study differences in results. Future vigilance research must consider these factors and explore working towards a single framework for studying vigilance, particularly within taxonomic families. Without consistency, cross-study comparisons are likely to be challenging and future observational work on other behaviours may also benefit from exploring these types of definitional issues. For baboons, operationalised definitions appear the most consistent across observers, however, future research should explore its application in other taxa.