Cats were not discussed in America’s first general pet reference guide, the 1866 Book of Household Pets, even though almost every household had one. But cats weren’t pets; they were seen, according to pet historian Katherine Grier, as "independent contractors," housed in exchange for controlling vermin.
Today, pets rarely have practical functions. According to the APPMA, the most frequently cited benefit of pet ownership—listed by 93 percent of dog and cat owners alike—is "companionship, love, company, affection." The second-most-cited benefit is "fun to watch/have in household," and the third is "like a child/family member."
Seventy-one percent of dog owners consider their pet a member of the family, as do 64 percent of cat owners, 48 percent of bird owners, 40 percent of small animal owners, and 17 percent of reptile owners. Even the scaly and cold-blooded, once brought into the home, can inspire parental affection.
Photograph by Alen MacWeeney/Corbis