In 1939 Mary Tudor, a graduate scholar on the University of Iowa, and her school advisor, speech professional Wendell Johnson, set out to prove stuttering might be taught via unfavorable reinforcement -- that it is realized behavior. Durham, N.C.: Duke University Press. Each individual within the trainer function was instructed to press a lever that may deliver a shock to their "learner" every time he made a mistake on phrase-matching quizzes.