In which direction does the dog's tail swing when it sees its owner

Everyone has seen the dog wagging its tail, and even the idiom "wagging its tail for mercy" has emerged, which shows that the dog wagging its tail is to win each other's favor. But sometimes when a dog is threatened, it wags its tail. What's the difference between the two?

An Italian scientist used a video camera to capture the process of a dog wagging its tail. The results showed that when a dog has a "positive" mood, its tail wags more strongly to the right; When there is "negative" emotion, it tends to shake to the left. Why?

It turns out that the left brain is related to positive emotions such as love and quiet, but it controls the movement of the right body; The right brain is related to negative emotions such as fear and depression, but it controls the movement of the left body. Therefore, when the dog is threatened, although it also wags its tail, it swings to the left.