The late Dr. Knight Dunlap made a lifelong study of habits and learning processes and perhaps performed more experiments along this line than any other psycholo­gist. His methods succeeded in curing such habits as nail-biting, thumb-sucking, facial tics, and more serious habits where other methods had failed. The very heart of his system was his finding that effort was the one big deter­rent to either breaking a bad habit, or learning a new one. Making an effort to refrain from the habit, actually re­inforced the habit, he found. His experiments proved that the best way to break a habit is to form a clear mental image of the desired end result, and to practice without effort toward reaching that goal. Dunlap found that either "positive practice" (refraining from the habit) or "nega­tive practice" (performing the habit consciously and volun­tarily), would have beneficial effect provided the desired end result was kept constantly in mind.
"If a response habit is to be learned, or if a response pattern is to be made habitual," he said, "it is essential that the learner shall have an idea of the response that is to be achieved or shall have an idea of the change in the environment that the response will produce . . . The im­portant factor in learning, in short, is the thought of an objective to be attained, either as a specific behavior pat­tern or as the result of the behavior, together with a de­sire for the attainment of the object." (Knight Dunlap, Personal Adjustment, McGraw-Hill Book Company, New York.)