The invention includes a teaching machine that presents questions to the user who responds with answers. Graded interval recall is accomplished by storing the exact time and date when the user learns a correct answer. The machine determines the presentation mode and review schedule for each unit according to the length of real time that has elapsed since the user learns the material. Precise timing is designed to bridge the threshold between short-term and long-term memory by interrupting default sequencing of material to review items at an exact preset interval from the time the user learned the material.