Animals are known to have amazing senses that let them see, hear, smell, taste, and touch their surroundings in unique ways. Chemoreception, or the sense of smell, is thought to be the oldest and most common of these senses in animals. People generally think that animals can smell human emotions, which is important because emotions are a key part of social interactions. But until now, only a small number of studies have shown for sure that animals can smell our emotions.
Plotine Jardat and her team did a study to see if horses can tell the difference between the smells people make when they are scared or happy. The horses were given the smells of sweat from people who said they were scared or happy while watching a horror movie or a comedy, respectively. A habituation-discrimination protocol was used, in which a first smell was shown twice in a row (habituation), and then the same smell and a new smell were shown at the same time (discrimination) (discrimination). Both smells came from the same person in the fear or joy condition, but neither the experimenter nor the observer knew this. The horses took longer to smell the new smell than the smell they had smelled before. This shows that they could tell the difference between the smells people make when they are scared or happy.
Also, the fact that the two smells make people get used to them at different rates and in different ways suggests that they make people feel different things. This study adds smell to hearing and seeing as ways that horses can pick up on human emotions and be affected by them. These ideas can change how horses and their owners, riders, or caretakers interact with each other.
This study gives us important information about how horses understand social situations and how they can smell our emotions. Domestic mammals like horses, dogs, cats, and goats can pick up on how people are feeling in a number of ways. They react to how people show emotion on their faces, and they can also tell how people feel from the sounds they make. Cross-modal experiments have shown that these species have mental representations of human emotions that include both what they see and what they hear. These species can also tell how emotional something is by how it looks or sounds.
Domestic mammals have been shown to be able to smell their own kind, and habituation-difference tests have been used to measure olfactory perception. Preference tests can also be used to measure how well a person can smell. For example, horses like the smell of feces from other horses that are more aggressive toward them. Dogs also acted more stressed out when they sniffed the body odors of their own kind that were made when they were alone, which is a stressful situation.
In the end, this study showed that horses can use their sense of smell to tell the difference between the smells people make when they are scared or happy. The results of this study give us important information about how horses understand social situations and how they can pick up on human emotions through different senses. These results have important implications for how horses interact with their owners, riders, or caretakers. More research in this area could also teach us a lot about how other animals understand social situations.
Jardat, P., Destrez, A., Damon, F. et al. Horses discriminate human body odors between fear and joy contexts in a habituation-discrimination protocol. Sci Rep 13, 3285 (2023). https://doi.org/10.1038/s41598-023-30119-8