In 1920 John B. Watson and Rosalie Rayner published the results of the study experiment describing how they had conditioned an 11-month-old boy (known as Little Albert) to fear a rat. The experiment is one of the best known and the most frequently cited empirical studies in the history of psychology. Many studies and theories suggesting the role of learning processes in the development of emotional responses were initiated by the Little Albert experiment. The article summarizes the procedures and results of the experiment reported by J.B. Watson and R. Rayner. The importance and impact of the results of the experiment on the development of psychological theories and research is discussed. Errors in the discussions of the Little Albert experiment in Polish psychological literature are identifi ed. The results of the latest historical research on the Little Albert experiment are summarized and their consequences are discussed