It has already been shown that dogs wag their tails asymmetrically when presented with different stimuli, and other dogs seem to behave differently when viewing left vs. right wags of robot tails . But do dogs actually have different emotional responses to viewing left vs. right-wagging dogs? To investigate this, several Italian scientists hooked dogs up to heart monitors and showed them movies of other dogs, some wagging to the left, and others wagging to the right. Interestingly, viewing dogs with left-wagging tails induced higher heart rates and more anxiety than viewing right-wagging tails, implying that wagging might be a form of communication not only between dogs and owners, but also between dogs themselves.

Seeing Left- or Right-Asymmetric Tail Wagging Produces Different Emotional Responses in Dogs.

“Left-right asymmetries in behavior associated with asymmetries in the brain are widespread in the animal kingdom, and the hypothesis has been put forward that they may be linked to animals’ social behavior. Dogs show asymmetric tail-wagging responses to different emotive stimuli-the outcome of different activation of left and right brain structures controlling tail movements to the right and left side of the body. A crucial question, however, is whether or not dogs detect this asymmetry. Here we report that dogs looking at moving video images of conspecifics exhibiting prevalent left- or right-asymmetric tail wagging showed higher cardiac activity and higher scores of anxious behavior when observing left- rather than right-biased tail wagging. The finding that dogs are sensitive to the asymmetric tail expressions of other dogs supports the hypothesis of a link between brain asymmetry and social behavior and may prove useful to canine animal welfare theory and practice.”

Source: Discovermagazine