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Advanced Spaced Repetition

the box as a system you keep for years

By now the daily loop is a habit. What breaks it over a year is everything around the loop: too much going in, a pile of reviews after a trip, and the few cards you never learn. This level is about that plumbing, and about when to leave the box closed.

  • Challenging to start
  • Life-Changing impact
  • Learn it in 30 days
  • An inbox, a cap and a bin
the system around the loop
A statechart of spaced repetition run as a system What you meet goes into an inbox only if it is worth a year. From the inbox you write one card at a time into the box, under a daily cap, and review the box each day. A card missed again and again goes to the leech pile, where you rewrite it and send it back through the inbox, or put it in the bin if it is still missed. After a week away the box goes to a backlog, which you clear with reviews only before going back to the box. A card you use without needing it is yours for good. what you meet [worth a year] into the inbox the inbox you write one card [under the cap] the box each day [missed again and again] the leech pile rewrite it [still missed] the bin [a week away] the backlog reviews only you use it [without the card] yours for good

The loop in the middle is the one you already run. Everything else decides what reaches it, how much, and what leaves it.

Set it up this month

Try it now.

Keep the box and the tally. Add these five rules around them, one part of the chart each.

  1. Ask one question before anything goes in

    “Will I want this in a year?” If yes, put it in an inbox: a note on your phone or a tray on the desk. If not, let it go.

    what you meet → the inbox

  2. Write one fact per card

    Empty the inbox once a week. A card that asks two things gets half-right answers you cannot mark. Piotr Woźniak, who made SuperMemo, calls this the minimum information principle.

    the inbox → the box

  3. Cap the new cards

    Each new card brings reviews for weeks after it. Pick the number of new cards a day you could keep up in your busiest week, and hold it.

    the box → each day

  4. Rewrite or bin the leeches

    A card you miss again and again: rewrite it with an example, a picture or a cue, and send it back through the inbox. If it still fails, bin it.

    the box → the leech pile → the inbox or the bin

  5. Clear a backlog with reviews only

    After time away, add no new cards until the due pile is back to a normal day. Spread it over several days rather than one long sitting.

    the box → the backlog → the box

For example: two years into Spanish, “to know a person” → conocer still fails every few weeks. It is a leech. Rewrite it with a cue: “I know María” → conozco a María. If that fails too, bin it. You will meet the word in your reading anyway.

When to leave the box closed

Three trays.

Not everything worth knowing is worth a card. Before the inbox, sort what you meet into one of three trays. Only the first one feeds the box.

Make a card

You need it for years and will not meet it every day.

  • Words for a language you will use for years
  • The names on a team you just joined
  • The formulas a course keeps building on

Use it instead

You will meet it daily, so use teaches it for free.

  • Your new phone number
  • The commands you run every morning
  • The way to the new office

Cram it

You need it once, soon. Spacing pays over months, not days.

  • Dates for a quiz you will not need again
  • A client's preferences before one meeting
  • A toast you give once (rehearse it aloud)

The idea

Why it works.

The spacing effect is one of the oldest findings in memory research, going back to Hermann Ebbinghaus in the 1880s. Later work, such as Cepeda and colleagues' 2008 study, found that the best gap between reviews grows with how long you need to remember. That is why the box suits what you want for years, and why it is the wrong tool for a quiz on Friday.

What wears a long-running box down is rarely the reviews themselves. It is what goes in: too many new cards, which come back for weeks; cards that ask two things; and the few cards missed so often they eat the session. Anki calls those leeches, and by default flags a card after eight misses.

Keep it running

Look after the box.

  • Mix your topics. One shuffled deck makes you tell similar things apart, which a deck per topic hides.
  • Teach a card. Explaining the idea to someone shows whether you know it or only the card's wording.
  • Delete without guilt. A card you no longer care about still costs a review every so often, for good.
  • Plan for time away. Stop new cards a week before a trip, and the backlog you come back to is small.

Go deeper

Keep going.

Practise this in HourLife.

In Learning: Resurface to remember. Track the books, courses, podcasts, videos and articles you are working through, log where you are, and keep what you take from them.

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