Dogs wag their tails in different directions depending on their emotions.

A wagging tail is typically considered a sign of a happy dog, but the truth is more nuanced. Research shows that dogs tend to wag their tails more toward the right side of their bodies when they encounter something they feel positively about, such as their owner, while their tails tend to move more toward the left when they encounter something unsettling, such as an unfamiliar, aggressive dog.

Dogs even seem to heed this difference in other dogs too: In one study, the canines became more anxious when they watched another dog wagging its own tail more toward the left. Researchers believe the difference in wagging direction may be related to the way the two sides of the brain process emotional information.