Cumulative Record. Chapter 12: The Science of Learning and the Art of Teaching. Quote 10

One of the most dramatic applications of these techniques has recently been made in the Harvard Psychological Laboratories by Floyd Ratliff and Donald S. Blough, who have skillfully used multiple and serial schedules of reinforcement to study complex perceptual processes in the infrahuman organism. They have achieved a sort of psychophysics without verbal instruction. (p. 182)