What's in a Wag?

If you think a dog wagging its tail is an unmistakable sign of canine happiness and affection, think again.

"If the tail is wagging to the right it's happy. If it wags left, it's something unpleasant for them," said Bill Berloni, an animal behaviorist with the Humane Society of New York.

Berloni echoes the claims of Italian researchers who say you can tell your dog's emotional state by the way it wags its tail.

Researchers found that dogs who saw their owners wagged their tails toward the right side of their bodies indicating they were happy. But dogs in more stressful situations wagged to the left side of their bodies, a sign of anxiety.

The study clearly applies only to certain dogs -- those that have tails.

ABC News tested the theory with stunt dog Otis, with Berloni calling the play-by-play at a local park.

"The beige-colored dog's tail is being chased. It's going to the left. When he barks it goes to the left, which is a sign of concern," Berloni said.

When owners called their dogs, their tails did seem to wag more to the right -- the happy side, according to researchers.

But Marc Surchin, one of the dog owners, isn't buying it. "I think it's kinda ridiculous," he said. "He's happy every which way."