Wagging the Dog: Some New Scientific Data on What Your Dog’s Tail Wagging Really Means

A dog wagging his tail is a happy dog, right? Not necessarily says Dr. Stanley Coren, author, well respected scientist and Professor of Psychology at the University of British Columbia. Coren points out that, among other things, “Science is always providing new information that allows us to interpret the behaviors of dogs, or to reinterpret behaviors which we thought we understood very well-such as the meaning of a dog's tail wagging.”

Myth one, Coren says, is that a wagging dog is a happy and friendly dog. “While some wags are indeed associated with happiness,” Coren wrote in a 2011 column on the subject, “others can mean fear, insecurity, a social challenge or even a warning that if you approach, you are apt to be bitten.

In some ways, tail wagging serves the same communication functions as a human smile, a polite greeting or a nod of recognition. Smiles are social signals and are thus reserved mostly for situations where somebody is around to see them. For dogs, the wag seems to have the same properties.”

Since dogs and humans have evolved together since time out of mind, and since many of our social structures are similar, it only makes sense that some of the signals we put into the world are similar, as well.

There’s more, though. Coren feels that, like any language, there is a vocabulary and even a grammar that must be understood. Traditionally, scientists looked at the tail’s pattern of movement and its position. More recently, however, they’ve also added “a third important dimension to understanding the language of the canine tail.”

Because dogs’ eyes are much more sensitive to movement than they are to details or colors, a moving tail is very visible to other dogs. Then there is the height at which at dog holds his tail, which Coren feels is kind of an s“emotional meter. A middle height suggests the dog is relaxed. If the tail is held horizontally, the dog is attentive and alert. As the tail position moves further up, it is a sign the dog is becoming more threatening, with a vertical tail being a clearly dominant signal.

As the tail position drops, it is a sign the dog is becoming more submissive, is worried or feels poorly. The extreme expression is the tail tucked under the body, which is a sign of fear. Coren points out that, when talking about tail position, it’s important to remember that the positions are all relative to where the dog normally holds his tail: something that varies greatly from breed to breed.

Tail movement is nuanced, too, says Coren. The speed of the wag indicates the level of excitement while the breadth of each sweep shows whether the dog’s emotional state is negative or positive. Coren says to look for the following combinations:

●  A slight wag-with each swing of only small breadth-is usually seen during greetings as a tentative "Hello there," or a hopeful "I'm here."
●  A broad wag is friendly; "I am not challenging or threatening you." This can also mean, "I'm pleased," which is the closest to the popular concept of the happiness wag, especially if the tail seems to drag the hips with it.
●  A slow wag with tail at 'half-mast' is less social than most other tail signals. Generally speaking, slow wags with the tail in neither a particularly dominant (high) nor a submissive (low) position are signs of insecurity.
●  Tiny, high-speed movements that give the impression of the tail vibrating are signs the dog is about to do something-usually run or fight usually. If the tail is held high while vibrating, it is most likely an active threat.

The most recent discovery, says Coren, is the most exciting. “It now appears that when dogs feel generally positive about something or someone, their tails wag more to the right side of their rear ends, and when they have negative feelings; their tail wagging is biased to the left.”

Coren stresses that it’s “important to understand that we are talking about the dog's left or right viewed from the rear as if you are facing in the direction the dog is viewing. That means that if you are facing the dog and drew an imaginary line down the middle of his back that positive right-sided signal would appear as tail swings mostly curving to your left.”

Dr. Stanley Coren is the author of many books including: Born to Bark, The Modern Dog, Why Do Dogs Have Wet Noses? The Pawprints of History, How Dogs Think, How To Speak Dog, Why We Love the Dogs We Do, What Do Dogs Know? The Intelligence of Dogs, Why Does My Dog Act That Way? Understanding Dogs for Dummies, Sleep Thieves, The Left-hander Syndrome.