Cats are the world’s most popular pets, outnumbering dogs by as many as three to one. This popularity is undoubtedly helped by the fact that cats are simultaneously affectionate and self-reliant... Even so, cats remain aloof and inscrutable. Dogs tend to be open, honest and biddable. Cats, on the other hand, demand we accept them on their terms but never quite reveal what those terms might be. Studies of dogs in the 1950s established the notion of a “primary socialization period,” when puppies are especially sensitive to learning how to interact with people. For dogs, this is between 7 and...