Spaced Repetition

Spaced repetition is a method used to remember things robustly, by revisiting them when you're about to forget them. The core insight is that after you encounter something the memory of it fades — but if you review it before you fully forget it, the memory fades a little slower the next time, until eventually it stabilizes. For example, if you learn a word in a foreign language, you may forget it within a day. If you review it within that period, it may take two days. Review it often enough and it sticks.

This is a simplification of how memory works — information that is immediately useful to you, that integrates into your mental networks, may stick immediately, while information you do not care for may fade almost at once. Nonetheless, it is a useful model, and a perfect fit for memorizing your anchor note in the Perfect Pitch game.