This handbook was created in response to a demand for a survey that would systematize, digest, and appraise the state of experimental psychology at the mid-century. The book is primarily for the use of graduate students, advanced scholars, and specialists, who may use it as a reference source and guide to material outside their special field of interest. It is a compilation of individual presentations by 34 outstanding contributors that covers new experimental data and theory in psychophysics, psychological mechanisms, growth and development, motivation, learning and adjustment, sensory processes, and problems of human performance. Each of the papers is fully documented, and a complete name and subject index is appended. The book should be particularly useful to specialists who do not have the time to fully cover the tremendous amount of new material that has been covered in journals in the field of psychology and related fields in recent years.