Nothing says “Welcome Home!” like the waggle of a dog’s tail. Tail wagging is synonymous with friendliness and love, contentment and delight. But is this long-standing association myth or fact? Leave it to sour scientists to spoil everyone’s happy hindquarters. Research suggests there’s more than smiles when your pup parades its rump. Here are five fast facts to help you better understand why dogs wag their tails and what those wiggles are trying to tell you.