Edwin Ray Guthrie focused upon a simplistic theory regarding learning. A Behaviorist, Guthrie believed that learning came about because of specific situations. He did not believe in reinforcement (positive or negative) or punishment. Instead, when it came to undesirable behaviors, Guthrie believed that changing a behavior was only a matter of creating a new behavior (to replace the undesirable one).
B. F. Skinner, another Behaviorist, is known for his ideas behind operant conditioning. In operant conditioning, behaviors are learned or made extinct through positive/negative reinforcement and punishment. According to Skinner, schedules of reinforcement must be maintained (in order to make a behavior become natural). In the beginning, continuous reinforcement is necessary. Over time, this schedule can be taken over by interval schedules (sporadic reinforcement).
While each behaviorist has his merits, I tend to follow Skinner more. As a teacher, the impact of positive and negative reinforcement is a far more powerful tool. Although each desired to change behaviors, a necessity to replace an unwanted behavior is not always necessary.