PITTSBURGH | Sometimes the way a dog wags its tail means more than you might have thought. But other dogs get it.
Expanding on its 2007 study that dogs wag to their right when feeling positive emotions and to their left when feeling negative, a team of Italian researchers is reporting that other dogs cue in to the tail-wagging signals.
The researchers, whose study was published Thursday in the journal Current Biology, showed that dogs, like humans, have asymmetrically organized brains, with the left and right sides playing different roles. A dog feeling a positive emotion, such as when seeing its owner, would process that in the left side of its brain, producing a tail wag to its right. Conversely, a dog feeling a negative emotion, such as seeing an unfriendly dog, would process that in the brain's right side, producing a left-side wag.
The researchers monitored the reaction of dogs watching videos of other dogs with either left- or right-asymmetric tail wagging. When the dogs saw another dog wagging to the left, their heart rates picked up and they began to look anxious. When dogs saw another dog wagging to the right, they remained relaxed.
So, a dog wagging with a right-side bias -- indicating a positive/approach response occurring in the left side of its brain -- would produce relaxed responses in other dogs viewing that. And a dog wagging with a bias to the left -- indicating a negative response and activating the right hemisphere of the brain -- would also produce an anxious response in a dog viewing the tail wagging, said researcher Giorgio Vallortigara. The neuroscience professor directs the University of Trento's Center for Mind/Brain Sciences.
Dogs "do not intend to communicate anything with such an asymmetric tail wagging," said Vallortigara, who holds a Ph.D. in cognitive neuroscience. "It is simply something that happens. The interesting thing is that such an asymmetric tail wagging seems, however, to have meaning for a dog looking at tail wagging of another" dog.
"Again, it is unlikely that this involves any explicit understanding by the observer dog."
Bias in wagging and its response might find practical uses among veterinarians, dog owners and dog trainers, he added.
"I can imagine they can be exploited, for instance by selecting a direction of approach to dogs during veterinary visits or in general when approaching a novel dog" or "making use of asymmetrical tail wagging" during agility or obedience teaching.
Penny Layne, a certified dog trainer in Irwin, Pa., isn't so sure. While the research may be valid, "I do not see any practical application," she said.
Layne was familiar with the theory about wagging to the right or the left but said there are so many other visible cues about what a dog is feeling that it doesn't make sense to her to focus solely on the tail.
"I don't dispute the research, but what I have is the experience of the last 22 years of studying dogs and training them ... and I'm reading more than just the tail.
"You really have to look for a while to see if the tail is going left or right. You can't waste that much time if your life is threatened. And dogs can't take that much time to determine if another dog is friendly or not friendly."
She said the issue of right or left wagging occasionally comes up. At a recent dog safety course she conducted, participants "wanted to know if there was any truth to the left or right tail wagging theory," she said. "I told them, 'I can tell you a dog wagging its tail in a full circle is a very happy dog.' "
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