DIED. B.F. Skinner, 86, a pioneer of behaviorist psychology; in Cambridge, Mass. Skinner advanced the concept that human and animal behavior can be shaped almost exclusively by the effects of stimulus and positive and negative reinforcement. In a series of laboratory experiments, he conditioned rats to press levers and pigeons to play table tennis by rewarding them with food. These feats occurred in the now famous "Skinner box," a soundproof enclosure with a food dispenser that a rat could operate by pressing a lever, and a pigeon by pecking a key. Skinner later applied his concept of programmed instruction to classroom teaching to improve students' reading, math and other skills through the reinforcement of praise. In his writings, including Walden Two and Beyond Freedom and Dignity, he called for restricting many individual liberties so that a Utopian society based on his principles of social engineering could be created.