Investigating the induction and measurement of equine positive affective state through a personality-centred lens

Abstract

This thesis explores the induction and measurement of positive affective state in equines via an exploratory approach, beginning with a three-round Delphi consultation of ninety-three experts worldwide. The Delphi worked towards achieving consensus on the development of a reliable assessment for equine personality and the determination of methods that could be used to induce and measure positive affective state in equines. Further work developed and tested the expert-devised personality traits assessment (a four phase, iterative process) to develop an equine personality questionnaire, the Equine Personality Eight-Factor Model. A pilot study was undertaken to refine the methodological design, and a subsequent full study was undertaken which utilised four potential induction methods for equine positive affective state, in a within-subjects, repeated measures, experimental design. Selected physiological measures (heart rate and heart rate variability, respiratory rate, eye and ear temperature and salivary cortisol) and behavioural measures (ear position, eye bias and position, Qualitative Behaviour Assessment and frustration responses) were utilised to attempt to measure affective state. Exploratory data analysis identified relationships between measures that may indicate the experience of positive affective state, whilst accounting for core personality traits; as well as measures that may indicate the presence of negative affective states. Suggested personality-based differences in responses to the four induction measures were also identified within the exploratory analyses. Results were considered within the framework of a four-quadrant arousal-valence model, providing suggested behavioural and physiological indicators of the affective states of reward acquisition, contentment, low motivation, and punishment avoidance. The conclusions drawn from this work provide a starting point for further explanatory research in this subject area, to enhance understanding of how we may optimise equine welfare through the provision of ethologically relevant positive experiences for equines and evaluation of their affective state alongside consideration of individual personality traits.