In this episode, we explore how stress in dogs reflects the stress of their human companions—but only for some breeds. Drawing on two studies by Lina Roth and colleagues, we examine how long-term stress synchronisation between dogs and owners is shaped by breed history, owner personality, and the perceived burden of dog ownership. One study found that herding dogs often mirror their owners' stress physiology, while another found that ancient and solitary hunting breeds do not show this same synchrony. Together, these findings offer a nuanced picture of emotional contagion and cooperation in the human–dog relationship.Key topics* Long-term stress synchronisation in dog–owner dyads* Differences between herding, ancient, and solitary hunting breeds* Role of owner personality in shaping canine stress* The impact of perceived costs in the human–dog relationship* Seasonal variation in dog stress levels* Implications for welfare and breed-specific understandingLong-read article Overview of the studiesThis article draws from two empirical studies published in Scientific Reports by research teams led by Lina Roth and Per Jensen, based at Linköping University in Sweden. Together, these studies investigate whether dogs reflect the long-term stress of their owners and under what conditions such physiological synchronisation occurs.The first study (Sundman et al., 2019) focused on herding breeds and was the first to demonstrate interspecies synchronisation of long-term cortisol levels—specifically, hair cortisol concentrations (HCC)—between humans and dogs. The second study (Höglin et al., 2021) expanded the inquiry to ancient and solitary hunting breeds, exploring whether similar stress alignment could be observed in breeds with different evolutionary histories and behavioural profiles.The core hypothesis tested across both studies is whether dogs mirror their owners' chronic stress—and if so, what variables influence this mirroring: breed, personality, sex, lifestyle, or the quality of the human–dog relationship.Dogs as mirrors: Synchronised stress in herding breedsIn the 2019 study, researchers recruited 58 dog–owner dyads, including Shetland Sheepdogs and Border Collies. Hair samples were collected from both dogs and their owners during the summer and winter to track cortisol levels over time. The primary measure—hair cortisol concentration (HCC)—offers a retrospective view of chronic stress over weeks or months, unlike saliva or blood which capture acute responses.Key finding: A strong, statistically significant correlation was found between dog and owner HCC across both seasons. The synchrony persisted even after accounting for lifestyle differences (e.g., pet vs. competition dogs), suggesting a robust interspecies alignment.Interestingly, the direction of influence appeared asymmetrical. Owner personality traits (measured via the Big Five Inventory) were significantly associated with dog stress levels, while the reverse was not true. For instance:* Higher owner neuroticism predicted lower dog HCC.* Higher conscientiousness and openness predicted higher dog HCC—but only in winter.* Dog personality traits (assessed via the Dog Personality Questionnaire) and activity levels did not significantly affect cortisol levels.This implies that dogs do not merely reflect shared environments or routines—they appear to internalise aspects of their owners' emotional world.Not all dogs mirror us: The case of ancient and solitary huntersThe 2021 follow-up study explored whether this synchronisation was a universal feature of the dog–human bond or one shaped by specific breed histories. It included:* Ancient breeds (e.g., Basenjis, Akitas) with genetic proximity to wolves and minimal selection for human cooperation.* Solitary hunting breeds (e.g., Elkhounds, dachshunds), bred to work independently, often at a distance from humans.Researchers used the same methodology—HCC from hair samples—but added several new layers:* The Monash Dog–Owner Relationship Scale (MDORS) to assess perceived emotional closeness, interaction quality, and the perceived cost of ownership.* Owner and dog personality questionnaires.* Lifestyle data, including kennel use, household composition, training routines, and physical activity.Key result: No significant correlation was found between dog and owner HCC in either ancient or solitary hunting breeds. Unlike the herding group, there was no physiological synchrony.This absence was not due to measurement artefacts. Dogs from these groups still showed variation in stress levels—but this variation was explained by other factors:* In solitary hunting dogs, dog HCC correlated with owner personality: lower agreeableness and higher openness were associated with higher cortisol levels in dogs.* In ancient breeds, owner personality had no clear effect, but there was a trend suggesting increased HCC in dogs rated as more aggressive toward people.* The perceived cost of ...
