Teaching machine
Teaching machines were originally mechanical devices. They presented educational materials and taught students. They were first invented by Sidney L. Pressey in the mid-1920s. His machine originally administered multiple-choice questions. The machine could be set so it moved on only when the student got the right answer. Tests showed that learning had taken place. This was an example of how knowledge of results causes learning. Much later, Norman Crowder developed the Pressey idea further.