GabyResearchers from the University of Bristol have discovered that human stress can lead to a sudden decline in a dog’s mood. This groundbreaking study by the university team is the first to demonstrate that the scent of human stress affects dogs’ emotions and behavior. While it may not come as a surprise to those who live with dogs, the researchers found that this ability is much stronger than previously thought. “Owners know how sensitive their pets are to human emotions, but here we show that even the smell of stress from a stranger can impact a dog’s emotional state, its perception of rewards, and its ability to learn,” said Nicola Rooney, the senior author of the study.
Since dogs can recognize both verbal and non-verbal signals from humans, the researchers decided not to expose them directly to stressed individuals. Instead, the dogs were given samples of sweat and breath collected from three unfamiliar volunteers while they were either relaxing or engaged in stressful activities. The relaxing task involved watching a nature video, while the stressful task included dealing with irritating instructions related to math and public speaking.
What the Researchers Discovered
The team involved 18 pairs of dogs and humans in the scent sample trials. During the training sessions, the dogs learned that a food bowl in one location always contained something tasty, while a bowl in another location was always empty. Those animals that grasped this concept approached the bowl more quickly when it was placed in the positive location P (associated with treats) than when it was in the negative location N (associated with the absence of treats). The scientists explained that the dogs’ active running between the bowls indicated their optimism.
In the second phase, the researchers placed the bowls in three new locations to confuse the animals. They then repeated the treat experiment while allowing the dogs to sniff the sweat of people in either a stressed or relaxed state (the sweat samples were contained in jars). The dogs approached the bowl in the new location hesitantly and with uncertainty when they detected the scent of a stressed stranger, sometimes even ignoring the bowl altogether. However, when exposed to the scent of a relaxed person, they eagerly set off to search for treats in the unfamiliar spots, as reported by Science Alert.
“Dog trainers often say that stress is transmitted through the leash, but we have shown that it can also be transmitted through the air,” said Mr. Rooney.
The reaction of the dogs exposed to the scent of human stress was classified by the researchers as pessimism. This negative emotional state may be adaptive, potentially helping dogs conserve resources or avoid frustration. Much of this dynamic remains poorly understood. The scientists will need further research to clarify how our scents influence dogs’ feelings and learning.
“Understanding how human stress affects the well-being of dogs is a crucial factor for animals kept in shelters, as well as for training companion dogs,” noted Nicola Rooney. The findings of the study were published in the journal Scientific Reports.
