A reasoned argument for the existence of animal mind, and a cautious exploration of that mind, by an animal-behaviorist-turned-sheep-rancher, author of Animal Behavior: Theory and Research. Mortenson sets out cards on the table at once: ""[The sheep] might be mere mindless bodies on a mindless mountain, fit only to be constrained and consumed. But in my heart, I know this is false--the sheep are as conscious as you or I."" But how does his heart, and then his head, know this? By observation and deduction. The author disdains Skinner and instead follows the lead of an obscure Darwinian, Margaret Floy Washburn, who pioneered the use of analogy to gauge animal consciousness. Mortenson sets out first to examine the mechanism and manifestations of consciousness in humans, and then to see if animals duplicate these phenomena; if so, he claims, then we can safely infer animal mind--and perhaps determine its nature. What follows is an energetic tour through the human brain and its chemical and electrical networks, with analogous systems popping up throughout the animal kingdom, especially in mammals. Then there's an intriguing classification of the manifestations of consciousness (sensitivity, orientation, exploration, learning, language): again, Mor-tenson discovers these signs of mind in abundance in most animals--particularly in gorillas, here represented by Koko, a female who communicates through American Sign Language with charm and wit (asked by her trainer to insult a human, she replies ""Sorry, gorilla polite""). Mortenson writes with lucidity and feeling, but it's unlikely that he will convince recalcitrant scientists, who will insist on harder evidence. As for pet owners and animal lovers, who already know that animals enjoy consciousness, the author's rare understanding of animal mind will prove an informative delight.