Abstract
Two main instructional practices are found in American education: One is prevalent, while the other is emerging. We have all experienced the prevalent practice, which results from the so‐called transmission model of instruction. In this model, students are exposed to content through lectures, presentations and readings, and are expected to absorb the transmitted knowledge in ready‐to‐use form. Although it is not a model of learning per se, the transmission model does make a pivotal assumption about learning, namely that the message the student receives is the message the teacher intended. Within this model, students' difficulties in grasping a concept are interpreted as indications that the presentation was not clear or forceful enough to be understood (that is, the signal being transmitted was either weak or garbled). Thus many users of the transmission model believe that if they make the presentation more lucid or persistent—for example, by transmitting at a slower speed or in a louder voice—students will eventually understand. Too often we are inclined to believe that by speaking in shorter words and sentences we can teach the big ideas in relativity to ninthgraders; this is simply not the case if the students' intellectual development is not at a level where they can appreciate the subtleties of difficult concepts.