The old comic strip “Sylvia” once posited that if humans could understand cat language, they would find that felines actually make only two different statements: “Hurry that dinner, willya?” and “Everything here is mine.”

Dogs, as any dog person knows, have a wider range of messages to transmit, which they do in all sorts of ways — barking, whining, tongue-lolling, mournful face-making, and of course tail-wagging. This latter means has attracted the interest of scientists in Italy, who put a lot of time into watching tails in action.

What they discovered is that dogs sometimes wag to the right and sometimes wag to the left. That may sound a confirmation of the obvious and meaningless, but the scientists concluded that the variation is not random.


A dog that wags rightward, they say, is relaxed and happy. A dog that wags leftward is anxious and under stress. Not only do dogs convey their emotional state with their tails, they can read the meaning when other dogs do it.

The subtle analysis may seem unnecessary, since detecting whether a dog is happy or unhappy is generally about as hard as telling if the sun is up or down. It doesn’t take a neuroscientist to interpret the meaning of a lick on the face. A growl is usually pretty self-­explanatory as well.

But the researchers say this revelation is important because it shows that — tiny and scattered as they sometimes seem — canine brains are asymmetric, with the left side devoted to particular functions and the right to others. This is a trait that they share with human brains. National Public Radio reported that Tom Reimchen, a biologist at the University of Victoria, “says there’s been a lot of work showing asymmetries in animals’ bodies, but ‘what has not been found is whether there is information that others can gain from that type of laterality.’ ”

This study provided an answer: Not only do dogs give away their emotional state with their tails, they can read the meaning when other dogs do it. Scientists don’t think, though, that dogs provide these signals deliberately. They’re just an involuntary response to stimuli — like, say, blushing.

Dog owners, of course, had always assumed their pets’ brains were asymmetric, with a great deal of space given to chasing squirrels, pulling on leashes and urinating on objects — leaving very little for the tasks of staying off couches and stepping around mud puddles. But then, dogs may have noticed how much of our mental capacity is needed for watching TV, compared with that devoted to throwing tennis balls.

We hope science won’t stop at this investigation of canine behavior. Ogden Nash once defined a door as “what a dog is perpetually on the wrong side of.” Researchers haven’t yet figured out why that is.

Still, the study is a useful reminder of how deprived people are in not having tails to wag. Dogs didn’t invent the emoticon, because they didn’t have to.