Woof! Woof! Woof! There it goes again, your neighbor's loud-mouthed dog. It's enough to drive you crazy.
You may as well stop complaining, because nobody has figured out a foolproof way to keep a raucous dog quiet. In fact, scientists can't even agree on why most dogs bark.
"It's because they're immature characters, like teenagers, very hard to train," says dog expert Raymond Coppinger, a biologist at Hampshire College in Amherst, Mass.
Unlike their wild wolf relatives, which stop barking as they mature, dogs develop into noisemakers because of domestication, Coppinger theorizes.
Coppinger once clocked a sheep dog in a remote Minnesota field that barked non-stop for seven hours. "I don't know if the dog is a record-holder, but I'm certainly the record-holder for listening without interrupting," he says with a rueful grin.
Almost anything can set off a canine barking jag. "Dogs can bark at the moon, the wind or the rustling of trees," says Mark Feinstein, a professor of cognitive science at Hampshire.
"Sometimes they bark when there appears to be nothing happening at all. There seem to be an astonishing number of reasons, and it's unusual in the animal kingdom, where most creatures tend to vocalize for a few specifics such as defending territories or finding mates."
Dogs that sound off because they have nothing better to do are called "boredom barkers," says Bonnie V. Beaver, chief of small animal medicine and surgery, Texas A&M University.
"Dogs are social," she said. "Keeping a pet shut up in the back yard without any human interaction isn't realistic. They're going to do something. They'll dig, bark, jump over the fence or run in circles. That's basically all they can do. You've got to look for what's driving the animal to a particular behavior."
The secret of dogs' communication lies in the pitch and frequency of their barking, says Stanley Coren, a psychologist at the University of British Columbia who has studied canine intelligence.
"A higher-pitched bark can mean a dog's frightened, and a lower tone can convey a threat," he says. "A quick burst of four or five barks, the kind you hear when someone comes to the door, means "Come over here, someone's invading our territory.' Then there's the bark with a stutter to it that's an invitation to play."
Some owners inadvertently turn Bowser into a loudmouth. The pet starts howling in the yard about midnight. "Shut up, you stupid mutt!" someone shouts.
"The dog gets rewarded with a voice response, so it barks even more," Beaver explains, "and eventually it gets to come inside. That dog's training its owners very well."
Reacting to complaints, many communities have passed anti-barking laws. "Of course, they don't stop dogs from barking," Beaver says, "but all of a sudden you've got a lot of frustrated owners looking for quick fixes instead of trying to deal with the initial problem of why their animals are barking."
Seeking instant cures, some dog owners have gone to such lengths as noise-activated devices that emit offensive odors or squirt water on offenders. A British inventor recently came up with a gadget that hangs around a dog's neck and emits a pungent lemon aroma every time the animal barks. Typical anti-bark collars produce unpleasant sounds or mild electric shocks.
Most such contraptions have one thing in common, the experts say: They don't work.
"Almost nothing will keep terriers from barking; it's in their genes," says Coren. "Everybody who owns a little terrier will tell you that its favorite game of all time is imaginary burglar. And it's always played between 2 or 3 in the morning, when in fact the dog is announcing that a leaf has fallen against the wall of the house."
But Coren is also convinced that canine heroes have saved many human lives with their clamor. "I tend to believe that barking dogs are often calling for help or alerting people, whom they consider members of their pack, that something is going on," he says.
Heroes aside, how do you silence a noisy dog? Coren has a soothing solution: "No yelling; you don't say a word. Instead, you just stroke the dog, sort of run your hands along his head, down along the side of his chest and maybe a bit along the back. The dog will interpret that as meaning "All's well, there must not be anything to bark about.' "