Our body language isn't the only way we communicate with our dogs. We also communicate with our dogs through their leash! This 6ft length of string that tethers us on our daily walks can offer a smorgasbord of information to our dogs - "get away from that," "let's go," "slow down!"- and potentially emotional information like stress, too. One recent study investigated whether our stress can affect our dogs when they are on a leash. They did this by telling one group of owner-dog pair to walk as they normally do (control) and another group of owner-dog pair that their walks would be judged by a panel of obedience experts (stress group). The study didn't find differences in salivary cortisol ("the stress hormone") between the two groups but that may be because this is only a mildly stressful situation for the owners.
The study DID find that the owners salivary cortisol was inversely correlated with their dog's. In other words, a stressed owner meant a less stressed dog! One explanation for this is that the stressed owner was more distracted and this lack of attention towards their dog allowed them more freedom on the walk. So while we do want to make sure our dogs stay out of trouble on their daily walks, it is equally important to allow our dogs some independence when we can. This may mean relaxing our attention on them, after-all how would you feel if someone were to watch and judge you on your dog's walks? Yikes!
These results may seem contradictory to studies that showed dogs respond in the same direction of our stress, but what it demonstrates is that while dogs can detect our stress, they are able to respond and regulate themselves depending on the situation. So a dog may experience an increase in cortisol in response to a crying baby and may respond in a way to relieve the stress in both parties, such as licking. While in this situation, dogs may respond by taking control of the situation because we are not in a state to do so...or dog's may use our distracted state to explore to their content!
Coppola CL, Grandin T, Enns RM (2006) Human interaction and cortisol: can human contact reduce stress for shelter dogs? Physiol Behav 87(3):537–541. https://doi.org/10.1016/j.physbeh.2005.12.001
Hare B, Tomasello M (2005) Human-like social skills in dogs? Trends Cogn Sci 9(9):439–444. https://doi.org/10.1016/j.tics.2005.07.003
Harvie, H., Rodrigo, A., Briggs, C. et al. Does stress run through the leash? An examination of stress transmission between owners and dogs during a walk. Anim Cogn (2021). https://doi.org/10.1007/s10071-020-01460-6
Yong MH, Ruffman T (2014) Emotional contagion: dogs and humans show a similar physiological response to human infant crying. Behav Proc 108:155–165. https://doi.org/10.1016/j.beproc.2014.10.006