Wag the dog

SINISTER v dexterous. Commie v Tory. The difference between left and right carries more meaning to human beings than mere matters of handedness and symmetry. And so it is with man’s best friend as well. For in dogs, too, left and right signal different things. Specifically, it is in the way they wag their tails. And for dogs, like people, it is the left-hand side that is sinister.

The story started a few years ago when Giorgio Vallortigara of the University of Trento, in Italy, and his colleagues, established that dogs wag their tails to the right when they see something pleasant, such as a beloved human master, and to the left when they see something unpleasant, such as an unfamiliar dominant dog. What Dr Vallortigara did not establish then was whether such signals are meaningful to other dogs. Now, he and the team from the previous study have done just that.