Dog's Tail Wag Says a Lot: What Your Canine is Communicating

You may think that a dog's wagging tail just means that he's happy to see you. But it turns out that a dog's tail wag means a lot more than that. Researchers have found that dogs recognize and respond differently when their fellow canines wag to the right than they do when they wag to the left. The findings reveal a little bit more about canine communication, and show that body language is important for man's best friend.

The findings actually are a follow up from previous work done by researchers that examined the way that dogs behaved when feeling different emotions. In that study, scientists found that dogs wagged their tails to the right when they felt positive emotions, such as seeing their owners, and wagged their tails to the left when they felt negative emotions, such as seeing an unfriendly dog. More interesting is the fact that this biased tail-wagging behavior reflects what is happening in the dogs' brains. Left-brain activation produces a wag to the right and right-brain activation produces a wag to the left.

Now, it seems as if this tail wagging behavior also means something to other dogs. In order to investigate this behavior a bit further, the researchers showed dogs videos of other dogs with either left- or right-asymmetric tail wagging. When dogs saw another dog wagging to the left, their heart rates picked up and they started to look anxious. When they saw other dogs wagging to the right, they stayed perfectly relaxed.

"The direction of tail wagging does in fact matter, and it matters in a way that matches hemispheric activation," said Giorgio Vallortigara, one of the researchers, in a news release. "In other words, a dog looking to a dog wagging with a bias to the right side-and thus showing left--hemisphere activation as if it was experiencing some sort of positive/approach response--would also produce relaxed responses. In contrast, a dog looking to a dog wagging with a bias to the left--and thus showing right-hemisphere activation as if it was experiencing some sort of negative/withdrawal response--would also produce anxious and targeting responses as well as increased cardiac frequency. This is amazing, I think."

The findings are important for understanding not only dog behavior, but also how brain activation influences body language. The researchers don't think that the dogs are intentionally communicating their emotions to other dogs, but they do believe that other dogs pick up on the involuntary response. Both dog owners and veterinarians might do well to take note of this particular body language.

The findings are published in the journal Current Biology.