Horses’ Social Evaluation of Human Third-Party Interactions

Abstract

Humans evaluate others by observing their interactions with third parties that are not directly related to the observers’ interests. Such third-party evaluations have not been well-studied in nonhuman animals. In this study, we investigated whether horses socially evaluate humans based on their third-party interactions. We used a helping paradigm similar to that used in earlier studies with dogs and cats: that is, the horses watched as an experimenter (attempter) tried unsuccessfully to open a container in order to remove an object and then asked another actor on his right (i.e., helper/non-helper) for help. The actor either helped the attempter or refused the request by turning away. After this interaction, the attempter repeated the same procedure with another actor on his left. The actor on the left played the opposite role to the actor on the right. After these two interactions, the two actors offered food to the horse simultaneously. The horses were able to freely choose which actor to take the food from. They showed no preference for the helper over the non-helper. Therefore, in line with the results from the first trials of previous studies in dogs and cats, horses may not have a robust third-party evaluation ability. However, future studies should use other paradigms that are more suitable to the social ecology of horses.