Dogs communicate with each other using their tails, and new research is helping to decipher what each tail wag means.

The direction of the tail wag — left or right — turns out to be very important, according to a study in the latest Current Biology.

While all wags look about the same to a glancing human, dogs are really clued into their direction and the hidden meaning behind that.

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When canines are distressed, such as when they see an unfriendly dog, they tend to wag their tails to the left.

This all occurs because the tail wagging is reflecting what’s happening in the dogs’ brains, according to lead author Giorgio Vallortigara, a researcher at the University of Trento’s Center for Mind/Brain Sciences, and his colleagues.

They found that left-brain activation produces a wag to the right, and right-brain activation produces a wag to the left.

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“The direction of tail wagging does in fact matter, and it matters in a way that matches hemispheric activation,” Vallortigara said in a press release.

“In other words, a dog looking to a dog wagging with a bias to the right side — and thus showing left-hemisphere activation as if it was experiencing some sort of positive/approach response — would also produce relaxed responses,” continued Vallortigara.

“In contrast, a dog looking to a dog wagging with a bias to the left — and thus showing right-hemisphere activation as if it was experiencing some sort of negative/withdrawal response – would also produce anxious and targeting responses as well as increased cardiac frequency. That is amazing, I think.”

As Vallortigara indicated, the study found that dogs that see another dog wagging to the left experience anxiety and increased heart rates. Dogs that see another dog wagging to the right stay perfectly relaxed.

The researchers don’t think that dogs are intentionally communicating with their tails, in the way that some humans communicate visually with sign language. Instead, they believe it’s more of a byproduct tied to the inner workings of doggy brains.

Nevertheless, the info is useful to dogs — and to humans — with the researchers calling on veterinarians to take note.

“It could be that left/right directions of approach could be effectively used by vets during visits of the animals,” Vallortigara said, “or that dummies could be used to exploit asymmetries of emotional responses.”

So don’t be surprised if, one day, you spot a realistic toy dog propped up at your veterinarian’s office, happily wagging its tail to the right.

Image: Siniscalchi et al.