Image for article titled Stressed? Your Dog Can Probably Smell It

A dog may be able to sniff out stress in humans. A small study shows that dogs can be trained to recognize the odors of stressed people and to distinguish them from non-stressful signals. The findings highlight the unique relationship between humans and canines and may have implications for training service and other types of working dogs.

Four dogs and 36 humans were recruited to participate in an experiment. They collected samples of sweat and breath from the humans under two different conditions, one of which was caused by the humans having to solve a hard math problem. The researchers only used the odors collected when people's blood pressure and heart rate went up.

The team introduced the dogs to the stressed samples and trained them to sniff one out. The dogs were exposed to a baseline and stressed sample at the same time along with a blank sample. The dogs were highly accurate at distinguishing a person's stressed odors from the others, with a combined 93.5% accuracy rate. The results are published in a journal.

Dogs can tell the difference between people's different emotional states. According to study author Clara Wilson, these studies have largely relied on looking at how dogs respond to visual or auditory cues of stress, or in studying dogs' biological responses to seeing human stress. Their findings show that our odors can shift when stressed, as well as that dogs can see it.

According to Wilson, the take- home message of the study is that our bodies' psychological stress response changes the smell of our breath and sweat, and that dogs can detect it.

Many dog owners claim that their dogs are very sensitive to their emotions and will often respond in a way that provides comfort in times of stress. Wilson points out that the findings don't show that dogs can comprehend the meaning of a person's emotional body odor. There is evidence that shows dogs mirror the emotions of their humans, a form of basic empathy. Dogs can read us because of our body funk.

Wilson said that the study adds supporting evidence that odor may have been a factor in relation to the previous study findings.

Wilson believes that the findings could be used to train service dogs and other dogs that have to work with humans.