Want to Decode Your Dog? It's All About the Wag

Tail wagging is more complicated than being a sign of a happy dog, new research shows. It not only indicates a range of emotions, but cues canines in to each other's moods. In study published in the Journal of Current Biology, scientists showed that the direction of the wag-more to the left or to the right-signals whether the dog is anxious or amicable, and, as significantly, found that other canines can read those signals and respond accordingly.

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The researchers previously published work that showed dogs wagged their tails predominantly to the right (from the dog's point of view) when they saw something that made them happy, such as their owner approaching, and more the left when they were stressed out by a larger dog or another stimuli they found threatening. The scientists wanted to investigate how other dogs might respond to the tail wagging.

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For dogs, like humans, the left and the right hemispheres of the brain are involved with different emotional responses. The right brain, which is associated with processing anxiety, controls left-sided movement while the left brain controls right-sided movement. Previous research has shown that dogs exhibit other types of lateral movement in addition to wagging. They turn their heads to the left when they see a dominant dog, and to the right when they see a friendly dog.

The researchers had 43 dogs watch videos of other dogs wagging their tails while wearing vests fitted with heart rate monitors. The images were manipulated for a clear directional wag. When the participating dogs watched a left wag (again, from the wagging dog's point of view) their heart rates rose and they looked anxious. When they saw a right wag, the dogs remained at ease and some dogs even approached the screen in a friendly manner. "We now know that dogs are reading each others' body language," John Bradshaw, an expert in anthrozoology at the University of Bristol, explained to the BBC.

Co-author of the study, Georgio Vallortigara, a neuroscientist from the University of Trento, said in a statement that he believes canines learn about each other's body language by experience. "If you have several meetings with other dogs, and frequently their tail wagging one way is associated with a more friendly behavior, and the right side is producing a less friendly behavior, you respond on the basis of that experience."

While dogs are more adept at reading each other's cues than humans, observant pet owners and veterinarians can use this information to help understand a dog's emotional state-and proceed with caution as necessary. "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," Vallortigara told NPR.

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