Why Do Dogs Wag Their Tails? Scientific Research

Why do dogs wag their tails that is the question which dog owners keep asking each other and the scientists as well. We won’t doubt it a second if someone told us that dog owners ask the same question while talking to their dogs. However, dog tail meanings is something that every Tom, Dick or Harry cannot interpret or understand. When a dog wags its tail, it might mean a lot of things. It does not only show their emotions, but it also shows their state of mind.

But before ever we share some scientific research with you, let us lighten our mood a little. So there is this odd and old joke about dog tail wagging. Jack was walking his dog Max in a local park when he happened to see a cute Irish Wolfhound staring back at him. The dog was wagging his tail and Jack thought of it as an expression of love and this made poor Jack go near the Irish geezer and it was the moment that Jack regretted the most for next one week; because as soon as he got any closer, the Irish dog took a huge bite out of his leg. Well, what can we say, Jack obviously barked up the wrong tree!

General concepts about why do dogs wag their tails

Let us not jump to complex and advanced scientific conclusions, and let us first consider the general concepts or misconceptions about dog tail wagging among the general public.

  • Happiness or excitement – When a dog is happy to see its owner or when it gets to eat its favorite food, it wags its tail to show happiness or excitement.
  • Fast wagging of tail vs slow tail wagging – Those people who have been dog owners for a long time, believe that while a fast tail wagging generally means that dog is either too happy or excited, a slow tail wagging is not a friendly gesture.
  • A big tail wag with a moving butt – Well-known veterinary and dog expert Dr. Lisa Radosta believes that if a dog is wagging its tail while moving its butt, it means that the dog is excited to meet a new person and willing to play with them.
  • Upward or downward tail wagging – Keen dog owners know how to decipher upward and downward tail wagging and they believe that as per dog tail meanings an upward tail wagging means that the dog is acting superior or dominant. It simply conveys one message to nearby dogs or humans “I am the boss around here!” However, if a dog wags its tail downwards, it means the total opposite of upward dog tail wagging. In other words, it means that the dog submits or gives up to superior dog or human.
  • Tail stiffness means a lot – As per Dr. Carlo Siracusa, irrespective of the types of dog tails or dogs breeds, a loose tail wagging is a friendly gesture, while a stiff wag shows the hostile feelings of the dog towards another dog or human[1].
  • Height of a dog tail wagging – Dr. Carlo Siracusa is also of the opinion that if a wagging tail is held high, it shows the enthusiasm and excitement to be friendly. To the contrary, if the wagging tail held low, it shows that the dog lacks confidence and self-esteem to be friendly and/or playful[2].
  • Gentle tail wagging – As per the general understanding of dog owners, a gentle tail wagging shows that the dog is greeting another dog or a human. On the other hand, vigorous tail wagging shows aggressive emotions.


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So why do dogs wag their tails? Let’s hear from researchers and scientists

As per the scientific research and studies, there can be many reasons for a dog tail wagging instinct. For a long period dog owners have been associating the dog tail wagging with expressions of happiness, loyalty and love. Poor them! They never thought that their dogs are smart animals and they can have much more complex expressions to convey. It was only until a few researches and studies that we finally learned that actually a dog’s tail between legs or an expression of tail wagging means a lot.

  • To reflect feelings: In 2007, researchers agreed with the common concept about dog tail wagging and declared that although dog tail wagging does not only mean happiness, but it definitely reflects their feelings[3].
  • To show energy and positive mood: In 2007, the research published in the journal of Current Biology, revealed that different portions of a dog’s brain show the dog tail wagging Scientists came to the conclusion that the left hemisphere of a dog’s brain controls the right side of its body and thus it controls the set of behaviors which scientists explain as a dog’s level of energy or its approach to certain things. They also concluded that a rightward tail wagging shows a happy and positive mood of a dog[4].
  • Amazing mode of communication: A very interesting research, conducted back in 2013, revealed that not only the dog tail wagging conveys messages to their human owners, but it also conveys different type of messages to other dogs, and they understand those messages by deciphering the asymmetric tail wagging of the communicating dog[5].
  • Roll of right and left brain hemispheres: Professor Georgio Vallortigara makes things more complicated. He conducted a research on dog tail wagging at the Centre for Brain Sciences, University of Trento, Italy and he came to the conclusion that it is not very easy to understand as to how and why do dogs wage their tails. He believes that just like right and left hemispheres of human brain dictate totally different type of emotional responses, a dog’s tail or tongue is also controlled by both hemispheres of its brain and there might be a clash, even competition for total dominance between both sides of a dog’s brain. Thus, we can never say this with surety if a dog tail wagging in circles has a certain meaning. Because in the event of such tail wagging coming from right hemisphere it will have a different meaning than that coming from the left hemisphere. Likewise, the dog tail anatomy has literally nothing to do with the reasons behind dog tail wagging[6].
  • To show friendliness or hostility: Professor Vallortigara’s research showed to the human beings and proved how a simple dog tail wagging can change the entire communication and send friendly or aggressive messages to other canines or human beings. For the purpose of their research, professor and his colleagues showed around 43 different dog tail wagging videos to a dog and they measured the heartbeat and physical responses of the dog to the actions of tail wagging. They noticed that when the dogs in the video wagged their tails slightly to the right, the guinea pig dog remained relaxed with ears hanging down and lips loose.

That is, the dog considered the right-ward dog tail wagging as a friendly message. To the contrary, when the dogs in the video wagged their tails to the left sight, researchers noticed a different behavior coming from the canine who was watching it. The heart beat increased all of a sudden, there were goose bumps the canine lifted its paws and showed others signs of anxiety and stress. Thus the researchers concluded that a left-ward dog tail wagging sends a negative message of aggression and hostility[7].

  • A learned and conditioned behavior: However, it is not that easy to understand why do dogs wag their tails. Tail wagging is not only used for very basic communication between one canine and another, or between a canine and its owner, but at times it becomes a learned behavior. Ivan Pavlov, the father of the conditioning theory, used dogs for his experiments and he proved that their responses can be conditioned. Dr. Lisa Radosta believes if dogs learn to keep themselves save, secure their territory or please their owner with a certain kind of tail wagging, they would get used to move tail in that direction and style, again and again. Thus she proves, that not only the left and right hemispheres of dog’s brain play a very vital role in dog tail wagging, another very important factor is conditioning.

Dr. Radosta is of the opinion that dog tail wagging does not necessarily have to be a result of brain functions, but another equally important reason can be conditioning. In such a situation a dog’s tail wagging would mostly depend on the stimulus and it will occur just as frequently as it will be exposed to the stimulus. To explain this concept, Dr. Radosta gives example of using a rectal thermometer to take a dog’s temperature. A dog exposed to this type of practices, would always use its tail to block the entrance of a rectal thermometer[8].

  • Intentional as well as unintentional gesture: Stephen Zawistowski of the American Society for the Prevention of Cruelty to Animals also says something along the lines of researchers and experts who believe that there cannot be a simple answer to why do dogs wag their tails? His opinion does not complicate the scenario and he does not refer to innate or learned behaviors, but he makes the phenomenon simple to understand.

He is of the opinion that a tail wag is just like a smirk on a human’s face. Sometimes we smile without knowing that we are smiling and without knowing the reason of that smile, and sometimes we smile intentionally, as a friendly gesture or just to appear in a happy and jolly mood. Likewise, a dog tail wagging can also be intentional as well as instinctive[9].

  • A skill for important purposes: This question of intentional or unintentional dog tail wagging brings us back to Dr. Racosta who believes that dogs do it on purpose. Unlike Dr. Stephen, she does not rely merely on theories, but she uses her everyday dog observations to form her conclusions. She believes that dogs always wag their tails with a clear message and intention, and it can always be observed in any dog park[10].
  • Defense mechanism: E’Lise Christensen Bell, a renowned veterinarian and expert on canine behaviors says that it is one classic fallacy to think that every time when you see a dog tail wagging, you think of it as a sign of a happy, excited or playful dog. She believes if the tail wagging occurs with goose bumps, stiffened muscles, tense expressions on face and ears tightened backwards or forwards, one must give the dog its personal space and back-off immediately. Dr. Bell is of the opinion that the tail wagging is a part of a very complex communication system in a canine’s life. Dogs accurately and flawlessly use their tail wagging to communicate with other dogs, and for the same purpose, they flawlessly observe the tail wagging and other bodily actions of the canines around them[11].
  • A set of canine behaviors: Beth Strickler, expert of Veterinary Behavior Solutions echoes with Dr. Bell and says that it is one big misconception to think that a dog only wags its tail when it is happy and in a mood of playing with other dogs or its owner. She makes a very valid point and refers to the children who confuse one dog tail wagging with another and eventually end up getting bitten by a dog. This shows how elementary is the human understanding of why do dogs wag their tails[12].
  • To maintain the balance: Covering all the possible reasons of why do dogs wag their tails, we must not forget one big and most certain reason: balance. Just like monkeys, dogs also use their tails to balance their bodies while running, jumping and chasing a prey. A dog wags its tail from time to time, only to maintain its bodily balance, and it does not always have to be a mode of communication.


So, ladies and gentlemen, whether you agree to one reason of dog tail wagging or another, it is pretty obvious that interpreting a tail wagging as a sign of a dog’s happiness or excitement, is only a bad idea. All you need to do is to stay away from a bad idea. Whether you are a cats person or a dogs fan, you must not try a dog’s patience or actually try anything new when you see a dog wagging its tail right in front of you.

However, if you are a dogs lover, just make sure to read as much about canine behaviors as possible, and while we are at it, consider this article only the first of its kind, while many are yet to come. Just keep in touch with us and share your valuable feedback; it’ll keep us writing and help us improve these articles.