A Laboratory Introduction to Psychology was written to acquaint the student with the concepts and methods of laboratory science as they apply to psychology. It is assumed that the laboratory course will follow or accompany a comprehensive course in introductory psychology which emphasizes scientific topics. The experiments have been related to journal articles and to sections of several popular textbooks so that students and instructors will have ready access to introductory material. This manual is limited to standard topics of experimental psychology, but includes some experiments that are relatively new. The topics discussed are grouped into in three main categories: Animal Behavior, Sensory Processes, and Human Behavior. Within each of these sections, the experiments are somewhat connected in shorter series. The Animal Behavior studies include one series consisting of conditioning, extinction, discrimination, and secondary reinforcement, and a second series on schedules of reinforcement and motivation. The experiments on Sensory Processes include some threshold measurements, and also a series of studies on perceived magnitude, adaptation level, and illusions. The experiments on Human Behavior include a series on learning and transfer, on short-term memory, and on two-person interactions.