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How to Decode Your Dog

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

Discover what's going on in your pup's mind with this article from our partners at Yahoo! Shine.

Tail wagging is not merely the sign of a happy dog, new research shows; it's more complex than that. A right wag often means something very different from a left wag. In a study published in the Journal of Current Biology, scientists showed that the direction of the wag signals whether a dog is feeling anxious or amicable. Just as significant, other canines can read those signals and respond accordingly.

Related: Cat Behavior Demystified: Video Translates Feline Language for Human Folks

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 to the left when they were stressed out by a larger dog or another stimuli they found threatening. The scientists, in this new study, built on that research by investigating how dogs might respond to the tail wagging of other canines.

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.

Read on to learn more about your dog's behavior.

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 to show 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 even approached the screen in a friendly manner. "We now know that dogs are reading each other's body language," John Bradshaw, an expert in anthrozoology at the University of Bristol, explained to the BBC.

Co-author of the study Giorgio Vallortigara, a neuroscientist from the University of Trento, in Italy, said in a statement that he believes canines learn about dogs' body language by experience. "If a dog has several encounters with other dogs, and frequent tail wagging one way [to the right] is associated with a more friendly behavior, and the left side is producing a less friendly behavior, dogs respond on the basis of that experience."

Dogs are more adept at reading each other's cues than humans are, but 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 probably be a side that is better with respect to the probability of evoking a more friendly response or a more aggressive response," Vallortigara told NPR. At first, it may be hard to determine whether your pooch is favoring its left or right side but watch closely.

—Sarah B. Weir

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