How Do Horses Appraise Humans' Actions? A Brief Note over a Practical Way to Assess Stimulus Perception

Heart rate (HR) is considered to be an effective tool for assessing animals' emotional response to a stimulus. We investigated changes in HR during a series of handling procedures (grooming test) in horses that had different experiences of human interaction. We used four groups of horses: grazing horses (group A), school horses (group B), six ponies, traditionally trained (group C), and six ponies, trained with modulated stimulus intensity (group D). An HR monitor was applied to each horse. The operator began the grooming test, standardized at the following points: (1) trainer's entry into the enclosure/paddock, (2) halter fastened, (3) start of grooming, (4) end of grooming, (5) saddling, and (6) inserting the bit. Group A repeated the grooming test twice: group A1 with a known operator and group A2 with an unknown operator. The data were compared by using analysis of variance (ANOVA) tests. The results showed a significant increase in HR (P ≤ .05) at point 2 compared with baseline in all groups except group D. Other significant differences were found at all points between groups A1 and A2, groups A2 and B, groups A1 and C, groups B and C, and at points 5 and 6 between groups A2 and C, as well as between groups C and D. Even when a scientific assessment of the increase in the HR is of primary importance, the use of this physiologic parameter may be helpful in assessing the horse's perceptions of stimuli presented by people during handling. Our results show that it is not the action “per se” that is important, but the manner in which horses perceive and appraise such actions in relation to the environment and their subject's experiences.