Masson begins by asking if we ever know precisely what another person is actually feeling. It may be no harder, he argues, to discover the truth about feelings in dogs. As human beings, we restrict ourselves with language, using a term as vague as 'I am depressed' to signal a highly complex set of emotions for which there is no exact equivalent. The joy that dogs exhibit when we return home is at least as complicated and hard to define, but the pleasure is evident, unconcealed and without the ambivalence with which humans seen cursed. Yet for all their evident loyalty, heroism and compassion, Masson highlights research which shows that dogs live in a universe of scent a hundred million times more acutely appreciated than by man. It is a world of emotions readily available only to other dogs. To discover more about the complex but transparent nature of canine emotional responses, Masson acquired three large dogs to form a community with his own family and set about a close scrutiny of their feelings - the first, he says, since Charles Darwin pointed us in the right direction 125 years ago.