Assessing Animal Welfare: A Guide to the Valid Use of Indicators of Affective States: Chapter 4 – Vocal signals

This chapter analyses if, based on current evidence, vocalisations have construct validity as indicators of emotional valence across species. It then explores the responsiveness and selectivity of vocalisation types, rates and acoustic parameters. The chapter presents guidelines and recommendations for best practice when assessing emotions using vocalisations, based on known indicators and when investigating a new species. It reviews the responsiveness and selectivity of vocal indicators of emotional valence. The chapter focuses on biological effects, rather than additional methodological issues like recorder proximity or the problems of comparing animals recorded indoors versus outdoors. Vocal indicators of emotions are also prone to selectivity issues, such as changes that are unrelated to emotional valence. The chapter also presents a case study of pig calls focusing on heuristic relationships between vocalisations and emotional valence. In some cases, vocalisations have been shown to induce emotional contagion, which plays an important role in group coordination and cooperation.