Dogs and Why They Wag Their Tails

Dogs Wagging Their Tails Can Mean Different Things

A dog who wags his tail isn’t always a happy dog. A wag of the tail doesn’t always mean that things are wine and roses for your pet pooch. What is your dog really communicating to you when he wags his tail? Italian researchers, who published their findings on Oct. 31 in Current Biology (see below), just might have discovered the meaning behind his tail wag.

No, the researchers haven’t discovered the equivalent of a Rosetta Stone that translates doggie dialogue into human languages and vice-versa. What they did was build upon their previous findings from a 2007 study about how dogs react by wagging their tails differently when they are placed into different social sorts of situations, such as meeting his or her owner, a stranger, a larger and more dominant dog, and potential prey, in the form of a cat.

In that initial study, the researchers noted that when meeting people,or cats,the pooches wag their tails towards the right. When they interact with strange dogs, and are put into an uncomfortable social interaction with them, dogs wag their tails to the left. The conclusion that the researchers reached then was that dogs wag their tails in a leftwards fashion when they are experiencing unease or are placed into social situations that are uncomfortable for them. A wag towards the right, on the other hand, meant that the dogs were in social interactions that they were more positive to them, like a reunion with their owners or the potential to have a bit of fun by chasing a cat.

The current study was an expansion of the initial one, in which the researchers studied the reactions — tail wags — of 43 canines who were placed in situations where they reacted to different stimuli they were introduced to, such as videos of dogs wagging their tails either to the left or to the right. The dog breeds included German shepherds, Rottweilers, boxers, border collies, mongrels, and beagles.

They were split into two groups, with one group being shown these videos, and the other group seeing the same videos, but in silhouette, so that they wouldn’t be influenced by other potential visual cues, like facial expressions. The researchers analyzed the reactions of the dogs in both groups, and also their heart rates.

According to the study’s author, Professor Giorgio Vallortigara of the University of Trento, the direction that a dog’s tail wags “matters in a way that matches hemispheric activation.” Explaining what he means,Vallortigara said that when dogs look at other dogs who wag their tails with a bias to the right side show “left-hemisphere activation.” These dogs would respond as if they were receiving a positive stimulus, which would “produce relaxed responses.”  Dogs and what the wags of their tails mean

However, when dogs were shown the videos of other dogs wagging their tails to the left, the right hemispheres of their brains were activated more, and they acted as if they were anxious, and experienced elevated heart rates.

Do the findings of the Italian researchers mean that dogs are intentionally communicating with each other via tail wags?

Dogs give each other many different signs and communicate both vocally, via barks, growls, whimpers, and other sounds, with other dogs. They also communicate non-verbally, by body posture, the positions they direct their ears, sniffing each other’s rear ends and other areas of their bodies, and the wagging of their tails (among other non-verbal signs).

Whether or not dogs are conscious that they are wagging their tails in a certain direction, and how much tail wags mean compared to other signals and odors, is somewhat a matter of interpretation.

Bernard College psychologist Alexandra Horowitz, who operates a dog-cognition lab located in New York City, has some doubts about the study. While intrigued by the findings, she is not certain that the tail wags were interpreted correctly, or if they were, if the interpretations hold true in all social interactions.

Are the dogs intentionally letting other dogs know about their emotional states? That’s another question that Horowitz is not convinced that the study’s results prove one way or the other.

In 2011, a different group of researchers came to the opposite conclusion, when it came to dogs interacting with a robot dog. Dogs more often chose to approach a robot dog which wagged its tail to the left, rather than to the right. This behavior would seem to negate the findings of the Italian researchers.

Horowitz asserts that one reason why the findings of the study that the Italian researchers conducted seems to be “genuine” is that the dogs in the videos other dogs watched “had quite a left/right wag bias.” Also, the elevated heart rates of dogs who saw videos “for left bias” doesn’t necessarily mean that’s how dogs would behave “actually seeing a left/right tail bias on another dog.”

One scientist who thinks that the study the Italians did has merit to it is Evan McLean, co-director of the Duke Canine Recognition Center. He believes that the decision of the Italian researchers to also use a silhouetted version of the videos helps give the findings more credence, because when dogs were shown these videos,according to MacLean, “we can clearly see that its the tail wagging that drives dogs’ responses.”

MacLean adds that the tail-wagging of dogs carries over to how they seem to interpret human facial expressions. They appear to be looking from one side of human faces to the other, “depending on the emotional state of the person.”

John Bradshaw, an expert on dog behavior from the University of Bristol’s school of veterinary science, says that the study of the Italian researchers seems to confirm that of another study regarding dogs turning their heads to the left or right.

For instance, he mentions a study done at the University of Lincoln. In that study, researchers discovered that dogs turn their heads to the right when viewing a happy dog, and to the left when looking at a dog who is acting aggressively.

Professor Giorgio Vallortigara, himself, is not necessarily convinced that the dogs are intentionally communicating by who their tails wag, though he believes that past experience has taught them which behaviors or moves that other dogs make should cause them to feel more concerned or relaxed. He states that, for example, if past experience teaches a dog that other dogs he or she sees who wag their tails to the right well then act in an unfriendly manner to them, the dog will “respond on the basis of that experience.”

What can be taken from the study of dogs that the Italian researchers conducted regarding the behavior of our own dogs?

The findings of the study which Professor Giorgio Vallortigara authored are interesting, though more study needs to be done to confirm that the left/right tail-wagging bias carries over to actual canine interactions.The results of the study gives dog owners, behaviorists, vets, trainers, and anyone else who has ever had an interaction with a dog a possible window into what the body language of dogs means.

Written by: Douglas Cobb
Current Biology

You must be logged in to post a comment Login