DON鈥橳 try diddling Fido out of his ration of Bonios. He can count. And when he barks, he may be trying to tell you more than you think.
Animals such as birds and rodents can tell when one pile of objects is bigger than another. But to count, an animal has to recognise that each object in a set corresponds to a single number and that the last number in a sequence represents the total number of objects.
Many primates have this basic mathematical ability. But Robert Young, an animal behaviour expert at the Pontifical Catholic University of Minas Gerais in Belo Horizonte, Brazil, suspected that dogs do too.
Advertisement
To test the idea, Young and his colleague Rebecca West of De Montfort University in Lincoln borrowed a technique that has been used to show that five-month-old babies can count. A number of toy dolls are placed in front of a baby and then a screen is raised to hide them. The infant then watches as some dolls are added or taken away before the screen is lowered to reveal the final result. If the experimenter has played a trick and surreptitiously added or taken away a doll, the baby looks at the dolls for much longer, presumably because he or she had done the calculation and the number of dolls contradicts the baby鈥檚 expectations.
Young and West repeated the experiment on 11 mongrels using doggie treats. Sure enough, the dogs stared at the bowls for much longer when the sums didn鈥檛 add up. Dogs paid little attention when one plus one treat resulted in two treats, the researchers will report in an upcoming issue of Animal Cognition. But they were confused when the experiment was manipulated to show that one plus one treat appeared to equal three treats, for example.
Dogs are descended from wolves, which not only have a large neocortex 鈥� the brain鈥檚 centre of reasoning 鈥� but live in large social groups. So their mathematical ability could, in evolutionary terms, have been useful for working out how many allies and enemies they had in a pack, says Young.
But there鈥檚 another reason to think dogs aren鈥檛 as dumb as they look. Animal behaviourists used to think their bark was simply a way of getting the attention of other animals. Now a new study suggests that individual dogs have specific barks with a range of meanings.
Sophia Yin, a veterinarian and animal behaviour expert at the University of California, Davis, recorded the barks of 10 different dogs of six different breeds. By analysing the sound spectrograms of more than 4600 barks, Yin discovered that dogs have different sounds for different situations.
When dogs are isolated from their owners, they tend to use high-pitched, single barks, Yin told the annual meeting of the Animal Behavior Society in Bloomington, Indiana, this month. When the doorbell rings, barks have a lower pitch, sound harsher and often fuse into one long 鈥渟uperbark鈥�. But 鈥減lay鈥� barks are high-pitched and unevenly spaced, often coming in clusters. Using the spectrograms, Yin was able to assign each bark to its specific context 80 per cent of the time for each dog.