This is a revision of An Introduction to Animal Cognition. The book reviews the main principles and experimental findings that have emerged from a century of research into animal intelligence. The book opens with an account of the various methods that have been used to study the intelligence of animals. The next four chapters then examine the contribution made by learning processes to intelligent behaviour. Topics covered include Pavlovian and instrumental conditioning, discrimination learning, categorisation, and an introduction to connectionist theories of learning. The second half of the book is concerned with animal cognition. There is a chapter on the representation of time, number and serial order. Additional chapters are devoted to memory, navigation, social learning, and language and communication. Issues raised throughout the book are reviewed in a concluding chapter that examines the way in which intelligence is distributed throughout the animal kingdom.