After reading this article, you may find yourself staring at your dog’s tail like it’s a mood ring with fur, you’ve been warned. However, it may make you feel better to know scientists, yes, people with PhDs have devoted years to decoding what your dog’s tail wag is really saying. And spoiler alert: it’s more than just “I’m happy!” In fact, the angle, direction, and even vibe of a tail wag can reveal a surprising amount about what’s going on in your pup’s head.

The Science Behind the Wag (Now Don’t You Wish You’d Been a Scientist?)

Back in 2013, researchers at the University of Trento in Italy set out to answer a question dog people have been asking since forever: What does that tail wag actually mean? Their study, published in Current Biology, found that tail wagging isn’t just a random happy dance. Dogs actually wag asymmetrically, more to the right when they’re feeling good, and more to the left when they’re stressed or unsure.

It turns out, this lopsided wagging has to do with the way dog brains are wired. Positive emotions are controlled by the left hemisphere, which sends signals to wag right. Negative emotions light up the right hemisphere, causing a left wag, similar in a sense to how the human brain has left and right brain function, our pups do too. Essentially, your dog is broadcasting their feelings in a dog version of Morse code, and we’re just starting to crack it.

But the plot thickens: other dogs pick up on this, too. In follow-up studies, when dogs saw another pooch wagging to the left, they got visibly tense, like someone just said “vet.” Right-wagging dogs? Much more chill. So not only is tail wagging a language, it’s one other dogs can read better than we can or at least most of them, we’ve seen a pup or two that aren’t the quickest on the pick-up!

The 2023 Update: Is It as Simple as That?

Fast-forward to 2023, when a fresh study published in Biology Letters(not what we’d call a recommended weekend read) reviewed over 100 prior studies on tail wagging. The findings? This tail talk is far more nuanced than previously thought. Wag speed, height, stiffness, and context all play a role in the message being sent. A loose, low, sweeping wag? Probably a friendly pup. A high, rapid-fire wag with a stiff tail? You might want to give that dog a little space (and maybe avoid making eye contact with their chew toy).

So what does this mean? Well, not all wags are created equal. We can think of tail wagging as the canine version of texting. A tail wag can say “Yay, you’re home!” or “Back off, I don’t like that energy,” or “Sorry, dang autocorrect, that’s not what I meant” depending on how it’s sent.

What Some Trainers Say

Some dog trainers are pretty into these studies that are wagging around. Many now observe tail direction and wag style as part of behavior assessments. For example, a trainer might note that a dog wags left whenever meeting new people, a potential clue that the dog’s not entirely comfy and could use slow introductions and some tasty bribes (aka treats).

It’s also helped trainers guide pet parents who misread signs of stress as signs of excitement. Spoiler alert: not every tail wag means “Let’s party!”

Humans: When Will We Learn?

A study out of Arizona State University put humans to the test, showing folks videos of dogs reacting to things like leashes, doorbells, and the universal enemy: vacuum cleaners. The takeaway? People are still reading dogs like a book in the wrong language. Most assumed the dogs’ emotions based on the context, not the actual cues the dogs were giving. In other words, we’re not as fluent in tail as we’d like to think.

What’s The Tail End of This?

So what does this all mean for us everyday dog lovers? We need to pay attention to the wag, not just the wagging. Is it left or right? High or low? Loose or stiff? Fast or slow? Combine that with the dog’s body language overall, and suddenly you’re not just a pet owner,  you’re a canine communications expert. (That’s a stretch, but you will be better anyway)

Next time your dog greets you with that tail helicopter, take a moment to check out the details. It might just be their way of saying, “You’re my favorite person,” or “I have deep concerns about your choice of shoes with that belt.”