On any given day, I am apt to observe my dogs. For hours, I may just be with them, watching. They delight me with their humor and they surprise me with their varied language. A few years ago, curiosity started me on a wonderful exploration into the canine vocabulary, and in the end, I created quite a stir with my research into the vocalizations dogs produce while playing. This line of inquiry began one afternoon while I was watching Goodall, my Briard puppy,who was about six months old at the time. Goodall is a whimsical dog, and on this particular afternoon, he was lying lazily on his side, spinning a swivel chair around and around. He would strike the chair with his front paws to start it spinning, and then he would use his hind paws to keep it going—a synchronized pattern of pawing and laughing.

That’s right, I said laughing. Until recently, it would have been career suicide to attribute this ability to anything but a human animal. But here was my little puppy, tossing his head back and producing a huh-huh-huh sound. The amount of air he forced out of his mouth was considerable, yet he was not exerting much energy while spinning the chair, so he wasn’t panting. I thought the sound may have meaning, and wanted to find out what that meaning was.

I asked other ethologists and animal behaviorists if they knew anything about dog laughter. Finally, at a conference in Chicago—“Animal Social Complexity and Intelligence,” 2000—Jane Goodall (after whom my dog is named) and Marc Bekoff (a scientist who has studied play in canids for over 30 years) suggested that I conduct the research and answer my own question. I took their advice, and what I found delighted me: Dogs produce all sorts of sounds during play. They growl, whine, bark and emit a forced, breathy exhalation through the mouth, a doglaugh, if you will.

Dogs also play-bow, paw, box and exhibit a relaxed mouth known as a play-face, or smile.When a dog smiles, the sides of the mouth are pulled far back and the lower jaw is slightly (or widely) open. The upper teeth do not show, but the lower teeth may be visible.When you see a dog smiling, it is an unmistakable expression.

Before my playback experiment to determine if the “forced breathy exhalation through the mouth” (the dog-laugh) had a discrete meaning, I examined the sound using spectrograph analysis. The sound of the dog laugh, which spiked to 44k cycles, looked very different than that of the pant, which is flat (see graphs at right, or go to laughing-dog.org to hear for yourself). These differences encouraged me to take the next step in the research, playing the sound to dogs and logging their responses.

Individually tested dogs responded to the dog-laugh by picking up toys and playbowing to the computer, the experimenter or the neutral dog. These responses contrasted to their reactions to recordings of growls, whines and barks; puppies piddled when they heard the growl, even though it had been recorded during play, while adults moved away from the growl and stood by the door. It appeared that the forced breathy exhalation meant a laugh and good times ahead!

This discovery was rewarding, but the other dog secrets revealed by my research were even better (to me at least).

Secret Number One: Dogs Are Fair-Minded