The Leitner Box

Spaced repetition is the finding that memory is strengthened most by a review that comes just before you would have forgotten, and that the safe gap doubles or better each time you get a thing right. Ebbinghaus measured the forgetting curve in 1885; everything since has been a way of scheduling the reviews so they land on the curve instead of too early (wasted) or too late (gone).

The Leitner box is the paper way to do it. Sebastian Leitner, a German science journalist, described it in So lernt man lernen (1972): a box of flash cards with dividers, where the compartment a card sits in says how often you look at it. Every card starts in the first compartment, which you go through every day. Answer a card right and it moves one compartment forward, to be seen less often. Miss it and it goes back to the first compartment, whatever box it had reached. Nothing is counted, nothing is dated; the position of the card is the schedule. A box that has been running a month sorts itself: the front compartment holds what is new or shaky, the back holds what you know, and your daily session is short because most cards are not due.

Writing the cards is half the learning, so let the learner write them where the hand can manage it. For a poem or a catechism answer, the face holds the first line or the question and the back holds the whole text; for a spelling word, the face holds the word said aloud by a parent (write it on the back only) or a picture; for a riddle, the face is the riddle, the back the answer and which move it uses; for a name from the Nomenclator, the face is the name, the back one sentence saying who or what.

A month of it looks like this. Compartment 1 is every day and is not written in.

1. Start small. Move at most ten cards a day from New into compartment 1. A box that starts with a hundred cards in the front collapses in a week.
2. The session. Go through compartment 1 every day, and whichever others the calendar names, back to front, so a card that is promoted today is not met again today. Say the answer aloud before turning the card. Honest grading is the whole game: nearly is wrong.
3. Right moves the card one compartment back, behind the divider. Wrong sends it to the front of compartment 1, with a tally mark. Do not argue with the rule; it is the rule that makes the box work.
4. Keep the front thin. If compartment 1 passes thirty cards, stop adding new ones until it is under twenty.
5. Graduate. A card answered right on two monthly reviews in a row goes behind Kept. Once a quarter, run the Kept cards once; any miss goes back to compartment 1, which is no shame.
6. Three or more tally marks means the card is badly written, not that the learner is slow. Rewrite it: split it in two, add a hook, or ask the question a different way.
7. Children under about eight do the box with a parent, who reads the face and judges the answer. The child moves the card; the hand remembers what the ear heard.

• The Promptuarium is a Leitner box on a screen: pieces to learn by heart, reviewed on a spaced schedule, graded Again, Hard, Good or Easy. A card that lives on paper can be banked there as well; the house adds nothing by itself, so you type it, and the two boxes run side by side.
• Ludus drills ten cards at a time with the same engine and shows the compartments as marks: a seedling for box 0 or 1, a tick for box 3 and above, a flag for anything missed since it was last mastered.
• Kept is the Memoria. A card that has graduated from the paper box is held word-perfect, and the house's rule for that is the vault: declare it, prove it a week later and a month after that, and it is kept for life, visited every few months. The Kept divider is the shoebox's door into the Memoria.
• Printed cards from the house. The six-catechisms page prints a catechism as 3×5 flash cards, question on the face and answer on the back; they go straight into the box behind New.

Print on card stock, letter size, at 100% (no "fit to page"). The dividers are 5 inches wide and 3½ tall, two to a page, with a half-inch tab across the top; cut on the solid lines, and cut away the dashed part of the tab row so only the labelled tab stands above the cards. The blank cards are 3×5, four to a page.

What you miss comes straight back. What you keep, you keep.