There’s More to Tail-Wagging Than Meets the Eye

bowingdogOne of the most basic and recognised pieces of dog psychology is via the trademark tail wag. Does your dog’s tail swish more to the right? Or, is your solemn pooch a left leaner? Scientists think they know what these subtle differences mean, and what’s more they’ve got evidence to show other dogs do too.


All dog lovers can tell you that their beloved pooches exhibit a wide range of moods and expressions which change depending on what’s happening around/to them. One technique of reading them is through the wag of their tail. You dog is calm and happy when the tail is being wagged to the right. If it’s wagging to the left, it’s indicative of fear. Low tail wags mean nervousness, and rapid tail wags mixed with tense muscles can be a sign of aggression.


Previously researchers have shown that dogs can convey their emotions through their facial expressions.   In a study published in the journal Current Biology, scientists have not only identified particular tail wagging patterns that can indicate your dog is feeling in a positive or negative way, but that other dogs not only see those patterns but react to them too.

This study builds on the previous research that indicates a dog whose tail wags to the right tends to be exhibiting calmness and is happy, whereas a left bias in the tail wags tend to signal anxiety and upset. To do this, the team of Italian scientists showed a group of 43 dogs wearing heart rate monitors movies of other dogs exhibiting different tail wagging behaviors. They also used a silhouette of a dog to remove any other physical signals.


What they found was quite intriguing, when the video showed the dog’s tail wagging slightly more to the right, the animals watching remained relaxed, with their ears hanging down, lips loose and eyes slowly blinking.  When the dog’s tail wagged to the left, however, the animals’ heart rate increased and their hair stood on end, they looked away, lifted their paws and showed other signs of stress.

The scientists don’t believe that this is a form of intentional communication but rather a way of reading body language in the same way that we humans unconsciously read others body language and react as appropriate. Professor Georgio Vallortigara, a neuroscientist from the University of Trento who was head researcher in this investigation, is quoted as saying he believes this reading of other dogs’ tail wagging behaviors is likely a learned ability: “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.”


As to why left and right tail wagging should signal such strong differences in emotional messaging, it appears to be a matter of what area of the brain is being engaged. “It is very well known in humans that the left and right side of the brain are differently involved in stimuli that invokes positive or negative emotions,” Vallortigara is quoted as saying. “In dogs, single organs like the tongue or tail is controlled by both sides of the brain. There can be competition and dominance between these two sides. When they move their tail, it is more bias to the left or to the right depending on which side of the brain is more dominant at the time. It seems dogs pick up on this when they meet other dogs and it forms a type of communication between them.”

How can this research help? It is hoped it will help dog owners, animal behaviorists and vets to better understand canine behavior. For example, it could be used to read and respond to a dog’s stress levels when visiting the vet or maybe dummies could be made to simulate calming tail wags to sooth a stressed dog — so don’t be alarmed if, in a few years, you walk into a vet’s office to find a plastic pooch wagging its tail to the right.


The researchers point out, however, that their tests were limited. As such, their future investigations will be geared toward assessing tail wagging among live dogs to see if this yields a more varied set of wagging behaviors.

Who knew that a dog’s wagging tail could be so interesting?


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