The dog has been man’s best friend for over 30,000 years according to anthropological evidence and DNA analyses. It stands to reason, then, that dogs have the unique ability to interpret human emotions.

Dogs have evolved in such a way, according to Scientific American, that they can “read” verbal and non-verbal signs of expression of their owners’ emotions, while previous research has shown that with the help of their keen sense of smell, they can detect the smell of stress in people’s sweat. A recent study has shown that dogs not only smell the presence of stress by releasing high levels of cortisol, but also react emotionally when they realize their owner is stressed.

How was the research done?

The new research, published Monday in Scientific Reports, by scientists at the University of Bristol in England, included 18 dogs of various breeds, along with their owners. Eleven volunteers who were unfamiliar to the dogs were put through stressful tests, including a public speaking and arithmetic test, while sweat samples were collected from under their armpits.

Participants then underwent relaxation exercises, which included watching videos depicting natural landscapes while seated in a comfortable chair under dimmed ambient light. New sweat samples were collected, three of these samples were used in this study.

The participating dogs were divided into three groups and smelled the sweat samples of one of the three volunteers. Before this the dogs were trained to know that in one location the bowl contained food, while in the other it contained nothing. There was also an ambiguous location in which the dogs did not know whether it contained a treat or not. When the dogs smelled the sweat sample from a stressed volunteer they were less likely to approach the bowl in one of the ambiguous locations. Previous research has shown that the expectation of a negative outcome reflects low mood in dogs.

Dogs have empathy: the evidence

The results suggest that when dogs are around stressed people, they are more pessimistic about uncertain situations, whereas when they are around relaxed people they don’t show this behavior, said Zoe Parr-Cortes, the study’s lead author and Ph. D. student at the School of Veterinary Medicine at the University of Bristol. “For thousands of years, dogs have learned to live with us and have evolved with us. Dogs and humans are social beings and so there is an emotional interaction between us,” she said. “Understanding that another member of the pack is stressed is considered a necessary advantage for dogs, as they are able to anticipate a potential danger.”

The fact that the smell came from a human unknown to the dogs shows the importance of smell to animals and how it affects their emotions in practical situations, said Katherine A. Houpt, associate professor of behavioral medicine at Cornell University College of Veterinary Medicine.

This research, Houpt adds, shows that dogs have scent-based empathy in addition to visual and verbal cues. And when you’re stressed, that could translate into behaviors your dog wouldn’t normally exhibit, she says. Additionally, it leaves us wondering how stress affects animals under the weight of a particularly anxious owner. “If dogs respond to milder stress like this, I’d be interested to see how they responded to something more severe like an impending tornado, losing your job, or failing a test,” says Houpt. “You would expect the dog to be even more attuned to a real threat.”