Your dog
is grinning.
Is it really
happy?

The full narration of the video.

Same open-mouthed grin. One dog is happy, the other is stressed. You walk in after work, and your dog looks up, mouth open, tongue out, like it's smiling at you. But inside, it might actually be on edge. So how can you tell? A small experiment at the University of Lincoln in England shows us. Let's walk through it.

They brought in twenty-nine Labradors and taught them one thing: run to a little window, and there's a treat. Most of the time, the treat came as usual. The dogs ran over, full of anticipation. But a few times, a clear panel covered the window. The treat was right there: visible, but out of reach.

The researchers went through the videos frame by frame, counting every little movement on the dogs' faces. It turned out the mouth opened and the jaw dropped more often when the treat was blocked. Blinking and nose-licking went up when the dogs were frustrated, too. That's odd. Why would a grin go with frustration?

Think of a dog's mouth as a computer's fan. Dogs barely sweat. When they're hot, tired, or worked up, they cool off by panting with their mouths open. So how wide the mouth opens is like how fast the fan spins: it tells you the machine is working hard, not whether things are going well.

When a computer is running a game smoothly, the fan roars. When it freezes, the fan roars too. To know which, you look at the screen. A dog's screen is its ears. In the same experiment, only one movement showed up more when the dogs were looking forward to the treat: ears pulled forward and up. When they were frustrated, the ears went flat and back.

Then check the body. A loose, wiggly body, soft mouth corners, tongue resting over the lower teeth: that's the closest thing a dog has to our smile. A stiff body, mouth corners pulled tight, licking its nose again and again: that's a dog saying, I'm not comfortable. This experiment looked at only one breed in one situation, so it can't speak for every dog. Still, checking the ears beats reading the mouth alone.

Here's something even more surprising. Arizona State University in the US showed four hundred college students videos of a dog. When everything around the dog was blacked out, leaving only the dog, people couldn't tell whether it was happy or sad. In another set, the dog was actually reacting to a vacuum cleaner, but edited to look like it was reacting to a toy, and people said it seemed happy.

So when we read a dog's mood, we're often reading what's around it, not the dog. Next time your dog grins at you, glance at its ears first. When your dog grins, are its ears up and forward, or flat and back?