In Donald R. Griffin takes us on a guided tour of the recent explosion of scientific research on animal mentality. Are animals consciously aware of anything, or are they merely living machines, incapable of conscious thoughts or emotional feelings? How can we tell? Such questions have long fascinated Griffin, who has been a pioneer at the forefront of research in animal cognition for decades, and is recognized as one of the leading behavioral ecologists of the twentieth century. With this new edition of his classic book, which he has completely revised and updated, Griffin moves beyond considerations of animal cognition to argue that scientists can and should investigate questions of animal consciousness. Using examples from studies of species ranging from chimpanzees and dolphins to birds and honeybees, he demonstrates how communication among animals can serve as a "window" into what animals think and feel, just as human speech and nonverbal communication tell us most of what we know about the thoughts and feelings of other people. Even when they don't communicate about it, animals respond with sometimes surprising versatility to new situations for which neither their genes nor their previous experiences have prepared them, and Griffin discusses what these behaviors can tell us about animal minds. He also reviews the latest research in cognitive neuroscience, which has revealed startling similarities in the neural mechanisms underlying brain functioning in both humans and other animals. Finally, in four chapters greatly expanded for this edition, Griffin considers the latest scientific research on animal consciousness, pro and con, and explores its profound philosophical and ethical implications.