Humans have been able to decipher messages about dogs wagging their tails... we see the fast wag, full-body wiggle as "I'm about to jump out of my skin, I'm so happy!" Then there's the tucked tail - a tell-'tail' sign the dog knows he's in trouble.
Researchers from the University of Trento, Italy, noticed a few years ago that there are subtle differences in how dogs wag their tails, listing to one side or the other. It was noted that when a dog sees something that makes them happy, such as seeing their owner, the wagging would tend to be to the dog's right. When faced with something uncertain, like an intimidating-looking dog, the tail would tend to wag to the left. Other measurements, such as heart rate, were used to gauge stress or anxiety, which corroborated the tail language.
These same researchers wondered if dogs viewing the tail wagging on other dogs would be able to read and respond to these visible cues. The test subjects were shown videos of other dogs with either left or right tail wagging. When dogs viewed a canine wagging to the left, the test subjects' heart rates sped up and they looked nervous. Conversely, when the wagging happened on the right, the heart rate only increased mildly, and the dog being tested looked relaxed.
One of the study's authors, Giorgio Vallortigara, doesn't believe that the dogs intentionally communicate with each other through the tail movements. He theorizes that dogs have learned from experience what body language signals they should and shouldn't feel worried about.
"If you have several meetings with other dogs, and frequently their tail wagging one way is associated with a more friendly behavior, and the right side is producing a less friendly behavior, you respond on the basis of that experience," said Vallortigara. Instead, the tail-wagging behavior stems from how different emotional cues activate different parts of the brain, he said.
Photo courtesy of fauxto_digit.