Some experiments in diagnostic teaching

Three teaching experiments are reported which study aspects of a diagnostic teaching methodology based on identifying key conceptual points and misconceptions, focusing on these, giving substantial open challenges, provoking cognitive conflict, and resolving it through intensive discussion. An experiment in the field of directional quantities showed a positive relation between the intensity of discussion and amount of learning; one on fractions and another on geometric reflections both showed — in comparison with individualized booklets, for which retention was very low — strikingly good two-month retention under the experimental teaching methods. The particular misconceptions found in each topic are also described.