Thanks to Discovery News for this interesting article.
Barking Dogs Have Something to Say
April 22, 2008 — The emotion conveyed by a dog’s bark often seems obvious to its human companions, but new research shows just how clear the message can be — at least, to other dogs.
The study presents the first concrete evidence that dogs can perceive the difference between barks arising from different situations.
While dog barking is hardly on par with human language in its complexity, experts now think it’s clear that dogs are conveying their feelings to humans and other dogs.
Dogs “express basic emotions, and we have not yet found signs for more complex meanings, like ‘this is the postman,’ ‘this is the bill collector,’ ‘this is the neighbor,’ etc.,” said co-author Peter Pongracz, who is a professor of animal behavior at Eotvos Lorand University in Budapest, Hungary.
“We might call this functionally referential communication, as we are able to tell what kind of situation could elicit a particular kind of barking,” he added.
Prior research conducted by Pongracz’s team found that people could indeed distinguish between different types of barks. For decades, however, dog experts were stumped as to how to prove dogs could do the same thing.
For the new study, which has been accepted for publication in the journal Applied Animal Behavior Science, Pongracz and his team found a way to do just that.
The researchers first recruited pet dogs of various breeds from training schools, to serve as listeners. Next, the scientists made recordings of Hungarian Mudi dogs barking during two different situations. One set of recordings was made when a stranger entered the property where a given dog lived. The second set was made when the dogs were tethered to a tree and left alone.
Two types of mechanical noise — an electric drill and a refrigerator — served as control sounds.
The scientists next outfitted each of the listening dogs with a heart rate monitor. While the sound of all dog barks caused a listening dog’s heart rate to jump, hearing a certain type of bark consistently over time stabilized the heart rate.
Even though they could get used to the distress barks, the listening dogs always showed a jump in heart rate when the researchers switched from one type of recorded bark to the other. This evidence for a change in attentiveness shows that not all barks sound the same to other dogs.
The researchers also think it’s likely that the dogs understand the different contexts producing the barks they hear.
Previously, other researchers thought domesticated dogs barked primarily for our benefit, since neither adult wolves nor feral dogs bark.