A dog will wag its tail to the right if it sees something it likes, and to the left if it sees something it doesn’t like. While hard to see without video analysis, it is one example of how both sides of the brain have different jobs in controlling emotions
“Specific tail wags provide information about dogs’ emotional state.Published on December 5, 2011 by Stanley Coren, Ph.D., F.R.S.C. in Canine CornerScience 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.Perhaps the most common misinterpretation of dogs is the myth that a dog wagging its tail is happy and friendly. While some wags are indeed associated with happiness, 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 tail wagging is meant as signal a dog will only wag its tail when other living beings are around-e.g. a person, another dog, a cat, a horse or perhaps a ball of lint that is moved by a breeze and might seem alive. When the dog is by itself, it will not give its typical tail wags, in the same way people do not talk to walls.Like any other language, tail wags have a vocabulary and grammar that needs to be understood. Up to now scientists focused on two major sources of information, namely the tail’s pattern of movement and its position. However new data adds a third important dimension to understanding the language of the canine tail.Movement is a very important aspect of the signal. Dogs’ eyes are much more sensitive to movement than they are to details or colors, so a moving tail is very visible to other dogs. Evolution has made tails even more visible, such as tails with a light or dark tip, a lighter underside or a bushy shape.The tail’s position-specifically, the height at which it is held-can be considered a sort of 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 meaning, “”I’m boss around here,”” or even a warning, “”Back off or suffer the consequences.””As the tail position drops lower, 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, meaning, “”Please don’t hurt me.””Just as there are different dialects to a human language, such as a southern drawl or a New England twang, there are also dialects in dogs’ tail language. Different breeds carry their tails at different heights, from the natural nearly vertical position common to Beagles and many Terriers to the low-slung tails of Greyhounds and Whippets. All positions should be read relative to the average position where the individual dog normally holds it tail.”