Heredity, Environment, and Personality: A Study of 850 Sets of TwinsThis volume reports on a study of 850 pairs of twins who were tested to determine the influence of heredity and environment on individual differences in personality, ability, and interests. It presents the background, research design, and procedures of the study, a complete tabulation of the test results, and the authors' extensive analysis of their findings. Based on one of the largest studies of twin behavior conducted in the twentieth century, the