A new Swedish study, involving 58 herding dogs and their female owners, suggests that the dogs tend to mirror their owners’ stress levels, rather than vice versa.
Previous research has shown that individuals can mirror each others’ emotional states — for example, there is a correlation between long-term stress in children and their mothers.
In the new study, published in the journal Scientific Reports, researchers from Linköping University (LiU) investigated whether similar mirroring of stress levels over long time periods can also arise between separate species, such as between the domesticated dog and humans.
The study involved 25 border collies and 33 Shetland sheepdogs, all owned by women. The team evaluated stress levels over several months by measuring the concentration of the stress hormone, cortisol, in a few centimeters of hair from the dog and its owner. The owners and the dogs provided hair samples on two occasions separated by a few months.
“We found that the levels of long-term cortisol in the dog and its owner were synchronised, such that owners with high cortisol levels have dogs with high cortisol levels, while owners with low cortisol levels have dogs with low levels,” said Dr. Ann-Sofie Sundman of the Department of Physics, Chemistry and Biology (IFM) at LiU, principal author of the study and newly promoted doctor of ethology.
Since physical activity can increase cortisol levels, the researchers also wanted to compare companion dogs with dogs that competed in obedience or agility. The physical activity levels of the dogs were therefore recorded for a week using an activity collar.
Previous work has shown that levels of short-term cortisol in saliva rise in a synchronous manner in both the dog and its owner when they compete together. In contrast, however, the new study found that physical activity in dogs does not affect the long-term cortisol in their hair.
On the other hand, the stress level of competing dogs seems to be linked more strongly with that of the owner. The scientists speculate that this may be associated with a higher degree of active interaction between the owner and the dog when they train and compete together.
The researchers also explored whether stress levels are correlated with personality traits. To do this, the dog owners were asked to complete two questionnaires to report their own and their dog’s personalities.
“Surprisingly enough, we found no major effect of the dog’s personality on long-term stress. The personality of the owner, on the other hand, had a strong effect. This has led us to suggest that the dog mirrors its owner’s stress,” said senior lecturer Dr. Lina Roth, also at IFM, and principal investigator for the study.
The findings suggest that the match between an owner and a dog primarily has an impact on the dog’s stress levels. Still, further studies are needed before any conclusions can be drawn regarding the cause of the correlation.
The researchers are now planning to study other breeds. Both the border collie and the Shetland sheepdog are herding dogs, which have been bred to collaborate well with humans and respond accurately and quickly to signals. The team is planning to explore whether a similar synchronization takes place between dogs and humans in, for example, hunting dogs, which have been trained to be independent. Another line of research will look at whether the sex of the owner plays a role.
“If we learn more about how different types of dog are influenced by humans, it will be possible to match dog and owner in a way that is better for both, from a stress-management point of view. It may be that certain breeds are not so deeply affected if their owner has a high stress level,” said Roth.
Source: Linköping University