Flashcards Deluxe
Leitner and Spaced Repetition 

Flashcards Deluxe has two advanced card order settings: "Short Term Goal / Leitner" and "Spaced Repetition".


Short Term Goal

This is the first of two smart study modes where cards that you get wrong will be tested more often. This is a good choice for when you have an exam in a couple weeks and need to cram quickly. Other benefits include being able to see your progress easily and being able to control the pace of your studying. The term "streak" is the number of times in a row you've gotten a card correct. This is a Leitner-based algorithm.

Spaced Repetition

This mode is perfect for storing information in your long-term memory. Most language students will use this mode. The study pace is set by the app, which tells you what needs to be practiced each day and helps push you towards your long-term goal.

"New" cards are the 10 cards that you are currently getting familiar with. When you've shown some proficiency with a new card (by getting it correct 3 times in row, or "strongly correct" once) it will become "active". Active cards have an "interval", which is the amount of time between testing. Answering correct will increase this interval, while getting a card wrong will decrease its interval.

There are 4 status values that a card can have:

Pending – cards waiting to become part of the 10 card new card (all cards start as pending)
New – cards in your 10 card "new" deck. When a new card is learned, it becomes active and a new pending card takes its place.
Active – cards currently being scheduled at intervals
Exclude – cards completely removed from the testing process

There are 3 sub-modes: (which may be selected automatically by the app, or may prompt you for)

New – In this mode, you practice just your 10 card new deck.
Due – You will be quized on active cards that are due to be tested again (meaning their interval is up). This is the main focus and strength of "Spaced Repetition": keep your studying efficient by studying cards at the right time so you don't under or over study.
Active (Leitner) – If you don't have any cards that are due, you can still continue to efficiently study active cards in a Leitner mode.

The above was an introduction to each Card Order option. The optional reading below are additional details of the Short Term Goal and Spaced Repetition process, which gets more technical as it goes on.

The Details

Short Term Goal / Leitner

Each card has a streak value, which is the number of times in a row you've gotten the card correct. A "strongly correct" response will increase the streak by 2 instead of 1, and getting a card wrong will reset the streak to 0. When you get a card correct the first time, it will skip 1 round before being shown again. If you get a card correct twice in a row, it will skip 2 rounds before being shown again, and so on. If you get it wrong, it will show up again the next round. Since progress is measured in rounds, or passes through the current study set, you can control your pace by going through one round a day, two rounds a day, etc.

Spaced Repetition - The Basics

This mode is similar to Leitner, except that cards are shown based on timed intervals, not on iterations through the deck. This mode is generally more effective than Leitner, especially for long term learning of many items. The logic here is similar to the programs SuperMemo or Anki.

The basic idea is each card has an interval, in hours. When a card is tested, you answer in one of three ways: wrong, correct (with some hesitation), or strongly correct (know well). Depending on the answer, the card's interval is updated, which determines when the next time the card will be tested again. Answering correctly will increase the interval, allowing you to focus more on the cards you miss. One great benefit of this mode is that you reduce the problem of over-practicing or under-practicing because the app will automatically determine when and what to test you on for best retention with the least effort.

Spaced Repetition - Practicing

When starting a deck, the first 10 cards become your "new" set and you will focus just on these cards. When you get a card correct 3 times in a row (its streak reaches 3) or you respond with "strongly correct", it becomes "active" and starts being scheduled at intervals. The reason for all this is that new and unknown cards need special attention as you start to learn them. When one card leaves the 10-card "new" deck and becomes "active", a new "pending" card takes its place.

Each card can have one of 4 status values: Pending, New, Active and Exclude. All cards start with a pending status. This just means they are waiting to become part of the 10-card "new" deck. Pending cards are not tested. A pending card will become "new" when a spot is available. If a new card is answered correctly 3 times in a row, it becomes "active". You can set any card to "exclude" status, which will remove it completely from the testing process.

Active cards can have two sub-statuses, due and non-due. A due card means that the interval is up (the last review date + interval < now). When you enter a deck, if there are cards that are due, they will have priority and be tested right away. If there are no due cards, and both new and non-due active cards exist, you have the option of learning more new cards, or practicing active cards. The recommendation is to learn new cards, as active cards will become due and tested again when the time is right, minimizing over-practicing. When practicing non-due active cards, Leitner logic is used.

At the bottom of the screen when going through the cards, you'll see something like "(1) 16h 2 3" The first number in parenthesis is the card's current interval in days (rounded). The next three show you what the card's interval will become depending on your answer: wrong, correct or strongly correct. In this example, if you answer wrong, the interval will become 16 hours. If you answer correct, the card will be tested again in 2 days. When you answer, you can start to think in terms of intervals if it helps demystify the process. If you find that cards are being scheduled too often, be more liberal with the "strongly correct" response. If you find that you are forgetting a lot of cards, use the "wrong" or "correct" (vs strong) more often.

• If you answer "strongly correct" on a "new" card, it will immediately become active.
• Statistics are generally not kept for new cards, so don't feel shy about answering incorrect.
• If you get an active card wrong, its streak becomes zero and immediately becomes due, even if the interval is not up yet.

Spaced Repetition - The Technical Details

The effectiveness of a system ultimately comes down to the details of the logic. I started with the basic concepts of systems like SuperMemo and Anki and refined them to my own liking. Often times, other programs schedule their intervals too long for my tastes, as my Chinese material is difficult for me and my memory-challenged mind, so I'll be interested to hear how others find my scheduling. If you have any feedback on my logic, I'd love to hear from you.

Generally, spaced repetition logic is about the interval calculation:
next interval = prior interval * factor. In my app, the factor is either 1.4 or 2.2 for correct responses. As you get a card correct the interval increases. For wrong answers, I use a factor of 0.5 which will cut the interval in half. I also re-test wrong answers right away.

Calculating a card's interval based from the response:

When a card moves from new to active:
correct: interval = 20 hours (1 day less 4 hours)
strong: interval = 3 days (less 4 hours)
So, the card will be tested next after either 1 or 3 days.

Active due cards:
wrong: interval = interval * 0.5
correct: interval = interval * 1.4
strong: interval = interval * 2.2

Active non-due cards:
wrong: interval = interval * 0.5
correct: interval = interval * 1
strong: interval = interval * 1

Non-due cards are tested only when there are no due cards and you choose to practice active cards. Why do I choose a factor of 1? Even though you got the card correct, I want to know that you can go the full current interval and still remember the card before increasing it. Cards that were just due but are being re-tested because they were wrong also follow this logic.

When getting a card wrong, the new interval is bound to a minimum of 8 hours and a maximum of 6 days. 8 hours in the lowest possible interval. If, for example, a card has an interval of 20 days and you get it wrong, it will get an interval of 6 days.

Finally, a card is due if either (last review time + interval < now) or streak = 0.