For dogs, good training and responsible ownership impact their behavior, but their life experiences and genetics can also affect temperament. Hormones may also play a role and could offer a new way to assess our canine companions. In a small study published today in the journal PLOS One, more well-behaved dogs generally had lower levels of cortisol—an important stress hormone—and higher levels of serotonin, a neurotransmitter associated with happiness.
A team at Kyungpook National University in Degu, South Korea, studied 24 dogs of various breeds, including beagles, border collies, and mixed breed dogs. They used a version of the Wesen test, an assessment that generally helps determine if an animal is more suitable as a pet or working dog. In this particular study, a human observer watched the dog’s reaction to several situations and interactions with people and other dogs. For example, the observer focused on how relaxed or anxious a dog appeared when they were alone and then around a total stranger. In another situation, the team assessed the dog’s attention, confidence, fear, interest, and relaxation during the Wesen test.
Some concerns exist that the Wesen test is too subjective, since it is based on an observer’s opinion. To look for more physical evidence, the team took saliva samples and measured the cortisol and serotonin levels. In animals, cortisol is released after “fight-or-flight” hormones like adrenaline to help keep the body on alert. It also helps regulate the metabolism and blood sugar levels. Serotonin is a neurotransmitter that carries chemical messages between the nerve cells in the brain and the rest of the body. It helps support several bodily functions including mood, sleep, digestion, and bone health. Earlier dog studies linked lower levels of cortisol and higher levels of serotonin with less aggressive behavior.
For these dogs, the salivary cortisol samples were taken both before and after the Wesen test. Those that scored higher for good behaviors tended to have lower levels of cortisol. These higher-scoring dogs also had a less marked spike in stress hormone levels after they were given the tests.
Sixteen of the 24 dogs had their salivary serotonin levels measured, but the results were not significant. However, the dogs with higher test scores did have higher serotonin levels before a test was given than dogs with lower scores.
Since it is such a small sample size of dogs, the team cautions that it does not show that hormone levels necessarily cause good or bad behaviors in dogs. It does provide some possible evidence that examining hormones and neurotransmitters could be a more objective way to measure a dog’s temperament than assessments like the Wesen test alone.
“Our study shows that physiological concentrations of hormones and neurotransmitters can serve as biomarkers of canine temperament,” the team writes. “These results could help identify dogs suited for specific working roles—such as military, police, guide, or therapy dogs—and assist in making better-informed companion dog adoption decisions.”
