Why Dogs Wag Their Tail to the Right or Left: Does Direction Matter?

Tricolor Shetland Sheepdog standing on grass with its bushy tail wagging to one side.

A dog’s tail swinging harder to one side than the other looks like nothing more than momentum, a body part following its own physics. But researchers have measured something odder underneath that motion: dogs wag more to the right when something draws them in, and more to the left when something makes them want to pull back, and that split has been traced to which side of the brain is doing the work.…