Studying the human-animal relationship allows to better understand how our behaviour can influence the one of animals. For example, it has been revealed that horses have exceptional sociocognitive skills toward humans. They perceive our emotions and they can detect our intentions. Recently, we showed that horses also respond to a kind of speech used to talk to companion animals, called pet-directed speech (PDS). Indeed, horses reacted more positively when an experimenter talked to them in PDS compared to adult-directed speech (ADS). Nevertheless, the mechanism underlying this response is still unexplored. In this study, we showed horses videos of humans using these two types of speech in order to determine whether PDS draws horses’ attention and arouses them, or if it helps to place them in a more positive emotional state. Horses showed higher attention and a greater increase in heart rate during PDS. However, their emotional expressions did not reveal a more positive state during PDS than ADS. We conclude that PDS improves horses’ attention toward humans and arouses them, so that this type of speech can be used by horsemen and horsewomen. Moreover, these results confirm that video projections can be used to study horses’ perception of humans.