Unwilling or willing but unable: can horses interpret human actions as goal directed?

Social animals can gain important benefits by inferring the goals behind the behavior of others. However, this ability has only been investigated in a handful of species outside of primates. In this study, we tested for the first time whether domestic horses can interpret human actions as goal directed. We used the classical "unwilling versus unable" paradigm: an experimenter performed three similar actions that have the same outcome, but the goal of the experimenter differed. In the unwilling condition, the experimenter had no intention to give a piece of food to a horse and moved it out of reach when the horse tried to eat it. In the two unable conditions, the experimenter had the intention to give the food to the horse but was unable to do so, either because there was a physical barrier between them or because of the experimenter's clumsiness. The horses (n = 21) reacted differently in the three conditions: they showed more interest in the unable conditions, especially in the unable clumsy condition, than in the unwilling condition. These results are similar to results found in primates with the same paradigm and suggest that horses might have taken the experimenter's goal, or even intentions, into account to adapt their behavior. Hence, our study offers more insights into horse interspecific social cognition towards humans.