Learning is a phenomenon that can be observed across the animal kingdom. ‘What is learning?’ considers the properties and principles of a number of different types of learning across a variety of different species. It begins by looking at one of the simplest forms of learning—habituation—before moving on to classical conditioning and instrumental conditioning. It discusses the famous experiment performed by Ivan Pavlov, in which dogs salivated to the sound of a bell. There is no generally accepted definition of learning, but quite a lot of what we understand by the term can be understood as ‘a relatively permanent change in behaviour as a consequence of experience’.