Dogs considered well-behaved tend to show lower levels of cortisol, known as the “stress hormone”, and higher levels of serotonin, often associated with well-being, according to a study conducted by South Korean researchers and published in the scientific journal PLOS One.
The investigation was conducted by Minjung Yoon, of Kyungpook National University in South Korea, and analyzed 24 dogs of various breeds. The animals were evaluated using the Wesen test, a method used to assess canine temperament based on observations of the dog’s reactions to different situations and interactions.
During the test, the researchers observed, among other aspects, the degree of anxiety or calmness of the dogs when they were alone or in the presence of a stranger, as well as levels of attention, fear, confidence, interest and relaxation. In parallel, saliva samples were collected to measure cortisol levels in all dogs and serotonin in 16 of them.
The results showed that dogs with better scores in the test generally exhibited lower cortisol levels before and after the evaluation. Additionally, in these animals, the cortisol increase caused by the testing situation was less pronounced. In the case of serotonin, dogs with better results showed significantly higher levels before the test was conducted, compared with dogs with lower scores.
Although the sample is small and the study does not allow establishing a direct cause-and-effect relationship between hormones and behavior, the authors argue that measuring cortisol and serotonin in saliva could become a more objective way of assessing dogs’ temperament, complementing or even surpassing the limitations of tests based solely on human observation.
According to the researchers, this approach could be useful in selecting dogs for specific roles — such as military, police, assistance or therapy dogs — and also help in making more informed decisions when adopting companion dogs.
