Not only can dogs smell diseases, but one study says they can smell stress, too.
Published in the journal PLOS One, researchers explained that “ previous research suggests that dogs can detect when humans are experiencing stress.” However, this study, led by Clara Wilson, wanted to take this one step further. Wilson, a doctoral student at Queen’s University Belfast, wrote about the study for The Conversation.
In her article, Wilson explains, “When people are stressed, there are hormonal and nervous system changes that alter the kinds of odors produced by the body.” With her colleagues, Wilson tested whether dogs could detect differences in samples from the same people, before and after a stressful event. Interestingly, Wilson says the team “took ideas from the field of biomedical detection dogs…and combined these ideas with techniques used to test dogs’ perceptions of odors.”
Smelling stress using household pets
In their study, heart rate and blood pressure helped measure subjects’ stress. Additionally, participants reported their stress before and after the study’s task. As stress inducers, the subjects quickly completed a mental arithmetic test. Before and afterward, researchers collected sweat and saliva samples from the subjects. Notably, the task was intentionally quick — four minutes, to be exact — to eliminate any confounding variables.
Interestingly, the study used pets volunteered by their parents. Before the study began, the dogs learned a specific way to let researchers know which sample they were picking. Amazingly, dogs learned to stand over the sample and freeze, a method researchers called “alert behavior.” Also, the dogs learned a matching game using two distinct odors to test their ability to distinguish scents. Once the dogs successfully completed the game, the experiment could begin.
Another win for dog noses
Amazingly, the study revealed that “the dogs correctly chose the stress sample in 94 percent of 720 trials.” At first, the dogs had to choose the stressed sample from two controls, which were both empty vials. But even after adding the relaxed sample to the mix, the dogs still consistently chose the correct sample.
Importantly, Wilson says “this study does not determine whether the dogs perceived the stressed samples as reflecting a negative emotional state.” Clearly, dogs can use all their senses to discern a situation. However, the study does show that their incredible sense of smell plays a vital role in the process.
