A dog uses its tail to express emotions. Though it’s commonly assumed that wagging of any sort is the effect of a rush of excitement from your four-legged friend, this isn’t true. Dogs actually have many different types of wags, including wags to express nervousness, anxiety, and even the sense of danger.
The emotion, or message, that a dog is expressing with their wagging is told by the position of their tails. Wagging that is high is a confident and playful gesture. Middle wagging means he is thoroughly excited. And a low wag is similar to a nervous laugh. A tail that is straight, with no wagging, indicates curiosity and focus.
A study done in 2007 found that the position of a dog’s tail isn’t the only indicator of his or her mood. The direction is directly linked to either a positive or negative emotion.
A tail wagging to the left indicates negative emotions, while a tail wagging to the right means your dog is in a positive state of mind. This was further proven in a 2013 study, that showed that a dog’s right-wagging sparked positive reactions from other dogs, while left-wagging made other dogs feel nervous and stressed.
The phenomenon is linked to the hemispheres of the brain. In some animals, the left hemisphere controls positive emotions and behaviours (like safety, food, and family), and the right side controls more negative emotions and behaviours (like danger and illness).