Currently, three theories of learning dominate classroom practice. First, B.F. Skinner's Theory of Operant Conditioning states that if behavior, including learning behavior, is reinforced, the probability of its being repeated increases strongly. Different types and schedules of reinforcement have been studied, by Skinner and others, and the programmed instruction system has resulted. This has yielded some success, but other research has shown that efforts to reinforce responses do not always work with all students. Second, Kurt Lewin's Cognitive Field Theory defines reality as the interpretations a person makes of self and surroundings as he or she interacts with them. Doing must be accompanied by a realization of the consequences and, thus, a teacher should be most concerned with producing personal involvement in the students, helping them to see a need to learn. Unfortunately, despite some helpful implications for teaching, Field Theory has little value in predicting what learning will occur under what conditions. Finally, Jean Piaget's Theory of Cognitive Development holds that thinking develops in a sequence of stages. Since it is assumed that children reason differently from adults, the teacher must try to see things from the child's point of view, which involves the difficult task of assessing the level and type of thinking of each child. Skinner, Lewin, and Piaget differ in their basic assumptions, but their work can be of great use to the teacher who employs common sense and the knowledge gained from classroom experience. (KH)