When dogs bark, humans understand

Between man and man's best friend, the lines of communication are open--at least, that's what a study in the May issue of the Journal of Comparative Psychology (Vol. 119, No. 2) suggests.

Ethologist Péter Pongrácz, PhD, of Eötvös Loránd University in Hungary, found that human listeners could tell whether a dog in an audio recording was acting aggressive, fearful or playful. The finding suggests, Pongrácz says, that dog barks play a communicative role in canine-human interaction.

Although it might seem simple, the question of why domestic dogs bark is still very much unanswered, Pongrácz explains. In the wild, other canines, like wolves, generally bark mostly as pups--as adults they do it only in hostile situations.

In the 1960s and '70s, many researchers thought that domestic dogs' barks were simply a leftover remnant of their juvenile stage that they didn't outgrow--and that they didn't have any communicative function. But recently, Pongrácz says, researchers have begun to rethink that view.

In his study, Pongrácz worked with Mudis, a Hungarian dog breed. He taped the animals--whose owners all belonged to a Hungarian mudi club--barking in six situations: when a stranger appeared at the door of the dog's house; when a trainer acting as a "bad guy" encouraged the dog to bark aggressively and bite a bandage on his arm; when the dog's owner picked up a leash and prepared to take the dog for a walk; when the dog was left alone in a park tied to a tree; when the owner played a game like tug-of-war with the dog; and when the owner held a ball or favorite toy a few feet in front of the dog.

Then Pongrácz played the recordings for 36 human participants--12 mudi owners, 12 owners of other breeds of dogs and 12 people who didn't own a dog. He found that all participants could correctly categorize the aggressive, playful or fearful emotions of the dogs at levels significantly above chance. He also found that there were no significant differences between the abilities of the mudi owners, other owners and nonowners.

"Our theory is that the dog is a very special, man-created animal," Pongrácz says. "It was shaped during many tens of thousands of years of domestication to live with people, so it's not surprising that this type of communication should exist."

Now, Pongrácz says, he and his colleagues plan to investigate how much of the human understanding of dog barks is innate, and how much is learned. As a first step, they're repeating the experiment with 5-year-old children.

--L. WINERMAN