A Queueing Network Model for Spaced Repetition

Flashcards are a popular study tool for exploiting the spacing effect -- the phenomenon in which periodic, spaced review of educational content improves long-term retention. The Leitner system is a simple heuristic algorithm for scheduling reviews such that forgotten items are reviewed more frequently than recalled items. We propose a formalization of the Leitner system as a queueing network model, and formulate optimal review scheduling as a throughput-maximization problem. Through simulations and theoretical analysis, we find that the Leitner Queue Network (LQN) model has desirable properties and gives insight into general principles for spaced repetition.