‘Man’s best friend’ is a common phrase about domestic dogs, referring to their millennia-long history of close relations, loyalty, and companionship with humans. It should come as no surprise that dogs are capable of intense feelings. As highly social, pack animals have their own social structures and bonding rituals, many mirror human social structures.
To your dog, you are family. What you feel, your dog feels.
There is no doubt that dogs can recognize emotions in humans. By combining information from different senses, they can abstract mental representations of their owners’ positive and negative emotional states.
For example, when dogs hear positive sounds, they look longer at positive faces, both human and dog. Moreover, if the owner is stressed, their dogs feel it too.
A new study by Linköping University suggests that the stress levels in dogs and their owners follow each other. In other words, dogs mirror their owner’s stress level.
The study arose from scientists speculating whether similar mirroring of stress levels over long periods can also arise between species, such as domesticated dogs and humans. The researchers determined stress levels over several months by measuring the concentration of a stress hormone, cortisol, in a few centimeters of hair from the dog and from its owner.
Ann-Sofie Sundman of the Department of Physics, Chemistry and Biology (IFM) at LiU, principal author of the study, said, “We found that the levels of long-term cortisol in the dog and its owner were synchronized, such that owners with high cortisol levels have dogs with high cortisol levels, while owners with low cortisol levels have dogs with low levels.
Researchers surveyed 58 dogs and their owners. Owners answered questions about extraversion, agreeableness, neuroticism, and openness.
They were also asked to complete surveys scoring their dogs on traits such as excitability, responsiveness to training, aggression, and fearfulness. The researchers then took hair samples from the dogs and their owners to test for the stress-related hormone cortisol.
Senior lecturer Lina Roth, also at IFM and principal investigator for the study, said, “Surprisingly enough, we found no major effect of the dog’s personality on long-term stress. On the other hand, the owner’s personality had a strong effect. This has led us to suggest that the dog mirrors its owner’s stress.”
“Cortisol is incorporated in hair as it grows, so we get a retrospective of our cortisol secretions.”
Researchers found that dog cortisol levels seemed to mirror the personality traits of their owners.
“The owner’s personality influenced the dog’s hair cortisol level, rather than the dog’s personality itself. The correlation was stronger between dogs and owners who compete than between owners and dogs who don’t.”
“When it comes to competing dogs, it could be that they spend more time together and that this training could increase this emotional closeness. This is a correlation, so we don’t know the mechanism behind this.”
“She would like to do follow-up studies on more dog breeds — this research focused on border collies and Shetland sheepdogs. She is also interested in how owner gender might influence the results. This study included only female owners.”
Rosemary Strasser, a behavioral neuroendocrinologist at the University of Nebraska, Omaha, who has studied connections between dogs and humans, says, “The new research is exciting, and it raises further questions about how dogs and humans influence each other emotionally.”
“One big question: Could dogs also influence human stress levels over time? Especially with dogs being used as service or support dogs for individuals, if you place a confident, outgoing dog in a home, how does it influence the personality of that owner? Is it always one-directional? That would be an exciting further extension of this.”
Further studies are, however, needed before we can draw any conclusions about the cause of the correlation. The researchers are now planning to study other breeds.
The study is published in the journal Scientific Reports.
