Dogs can learn a lot by observing how another dog's tail is wagging, according to a study recently published in the journal Current Biology.

Through the study, reported on by NPR, researchers learned that dogs tend to become uneasy when they see the likeness of a dog wagging its tail to the left side. Dogs remained more relaxed when the image of the dog wagged its tail to the right side, researchers said.

Previous studies from researchers at the University of Trento in Italy have already shown that the way dogs move their tails varies depending on whether they perceive something as friendly or threatening, but they still wanted to learn if dogs can detect the meaning behind how other dogs wag their tails.

Study design and findings

Researchers selected 43 dogs to participate in the study. The dogs were outfitted with vests designed to capture changes in their heart rates as they observed tails wagging in different directions. 

Some canine study participants were shown still images of real dogs with tails that could be moved to the right or left. Other dogs were shown a video featuring the silhouette of a dog with a movable tail.

According to researchers, dogs observing another dog with a tail wagging to the right remained calm. A tail that wagged to the left caused elevated heart rates and anxious behavior in participants, researchers said.

From the results, researchers concluded in the study abstract that "dogs are sensitive to the asymmetric tail expressions of other dogs supports the hypothesis of a link between brain asymmetry and social behavior and may prove useful to canine animal welfare theory and practice."

Practical applications for veterinarians

Beyond explaining more about how dogs perceive certain social signals, the information gained from the study might help veterinary staff members modify their interactions with dogs to keep the animals calmer, said Giorgio Vallortigara, from the University of Trento.

"These results suggest that dogs have perceptual and attentional asymmetries," Vallortigara told NPR. "So for example, if you are going to visit a dog, if you are vet, there will be probably a side which is better with respect to the probability to evoke a more friendship response or to evoke a more aggressive response."