The document discusses spaced repetition and forgetting curves in learning. It finds evidence of a forgetting curve where recall decreases over time since initial learning. Accuracy on review problems is predicted by factors like correctness during initial learning and problem difficulty. Simulations show it takes more practice problems to achieve proficiency at lower accuracy rates. Code examples in R are provided to analyze spaced repetition data and create plots.

1. Learning, and Forgetting (not necessarily in that order)

4. Forgetting Curve R = % Recall t = time S = Strength of memory

8. The Result: Evidence of a Forgetting Curve