Human beings may have their own take on what canine body language may mean to them but a recent study, out of the University of Trento, in Italy, shows that tail wagging serves as an emotional communication cue between dogs. And whether a dog’s tail wags more to the left versus right makes a world of difference in the affective response of observant canines.
Lead researcher Giogio Vallortigara began exploring tail wagging behavior several years ago when he and his colleagues established that dogs tend to wag their tails to the right upon seeing something pleasant, such as their human master, and to the left when they encounter an unpleasant stimulus, like an unfamiliar dominant dog. What was not studied was if tail wagging itself, especially the distinction between right and left orientations, had any emotional effect on other dogs, thus serving serving as a communication signal.
Vallortigara’s latest research, published in Current Biology, set out to address the question of whether or not tail wagging served as a meaningful signal of communication between fellow canine creatures. In order to carry out the study, the researchers monitored the heart rates and other physical responses of subject dogs who were shown head-on videos of other dogs in one of three postures; either sitting motionless, wagging their tail to the left, or wagging their tail to the right.
When shown videos of dogs with right-wagging tails, the subject dogs remained relaxed, with loosely hanging lips and ears, and a normal heart rate, much the same as when they were shown dogs in a stationary position. Left wagging tails, however, induced signs of stress such as increased heart rates, flattened ears, lowering of the head, hair standing on end, and whining. Professor Vallortigara does not attribute any conscious awareness of these signals to the dogs but posits that the responses are automatic and reflect the lateral specialization of the dog brain.
The dual hemisphere brain of the human being has undergone much study over the last century and, even among lay people, it is fairly common knowledge that the right brain controls right-sided physical movement (and vice-versa) and that the right hemisphere tends more towards specialization of spatially oriented events such as images, while the left brain specializes in logic and linear thinking.
Vallortigara suggests that the same general concept may apply to dogs and that the significance of this particular study may be to intensify research in the study of the lateral specialization of the canine brain. In fact, he postulates that the physical effects of right versus left tail wagging may be due to the stimulation of whatever brain hemisphere responds to the right or left visual field, a sort of hard-wired communication system of pure body language.
So, as it turns out, a dog who wags it tail may not necessarily be happy and relaxed; it may just as well be experiencing an unpleasant anxiety. But, even further, whether its bliss or torment, the communication of tail wagging transmits these physical and emotional states between dogs.
By Robert Wisnewski