In the mid-1800's, Charles Darwin postulated that dogs could think and even communicate with each other, guided by certain rules of morality. Other scientists scoffed at the idea until a recent, serious study of dogs at play. It turns out that dogs recognize honesty and deceit, show compassion, and ostracize other dogs that don't play by the rules. In some ways, they outsmart our closest relatives — chimpanzees. That's according to a new field of animal research, discussed in Citizen Canine: Our Evolving Relationship with Cats and Dogs. The author is David Grimm, deputy news editor at Science magazine.