Behavior of Organisms
B. F. Skinner's 1938 book, the one that established operant conditioning as a research programme. Working with rats in the apparatus that became known as the Skinner box, he separates operant behaviour, emitted and then shaped by its consequences, from the reflex responses Pavlov studied, and builds the account of reinforcement schedules from cumulative response records. It is a laboratory monograph rather than a popular argument, and everything Skinner wrote afterwards rests on it.