Scientists have tested whether dogs and their owners synchronise their stress levels. The scientists, from the Linkoping University in Sweden, hypothesised that because dogs and their owners live so closely, that their emotional states could be contagious. The results of the study, which aimed to prove that there could be an interspecific synchronisation in stress levels, long-term between humans and dogs, were published in Scientific Reports as an open access article.
The scientists asked 58 dogs and their female humans to participate in the trial. The human-dog pairs were assessed for their personality traits through an owner-completed Dog Personality Questionnaire (DPQ) and the human Big Five Inventory (BFI) surveys. The scientists also monitored the dogs’ activity levels through a remote cloud-based activity collar for one week. The dogs were either Shetland sheepdogs (33) or border collies (25) and the number of each gender was balanced. Dogs used to competing in agility and obedience and normal pet dogs were both recruited so that different lifestyles were represented. The scientists chose to determine the level of stress experienced by both dogs and owners through the analysing of hair cortisol concentrations (HCC) on two different occasions in summer and winter. Cortisol from the blood is gradually incorporated into hair as it grows, which can enable scientists to study long-term stress synchronisation. Previous studies have shown a correlation between the stress of mothers and their children through hair cortisol concentrations.
The scientists hypothesised that when dogs and their owners train to compete, this can increase the emotional closeness of dogs and their owners which could also synchronise their stress. Competitions could be seen as one source of stress. The production of cortisol can also be affected by exercise, so the owners were asked to report on activity, as well as the dogs wearing remote collars which could monitor their activity.
The scientists concluded that there was an interspecific long-term stress hormone synchronisation between the dogs and their humans. They found that there was a seasonal effect where the dogs’ hair cortisol concentrations were higher during the winter months. The scientists felt that the humans’ personality influenced the dogs rather than the other way round. The shared physical activity during a competition certainly influenced the shared stress levels, but synchronised stress levels were found long-term in both humans and dogs, and pet and competing dogs too.
Although the synchronisation was strong for both male and female dogs, it was stronger for female dogs. Competing dogs and owners shared more synchronisation, but it was not linked to the dogs’ physical activity measured by the smart collars or the training frequency. Owner specific traits including Neuroticism (both summer and winter), Openness and Conscientiousness (winter samples only) were more likely to influence hair cortisol concentrations in their dogs. However these were more likely to be the Shetland sheepdogs. The dogs’ personalities seemed to have little effect on their HCC.
The scientists suggested that future studies try to remove seasonal effects to ascertain whether the dogs truly reflect their owners’ stress levels.
Roth, L.S.V., et al., Long-term stress levels are synchronised in dogs and their owners, Scientific Reports, June 2019, Article No: 7391