Gilad Naor


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Learning Japanese - Spaced Repetition Software

Note: this article is part of a series on how to memorize  
material. You can start at: [Learning Japanese - Memorization](/2009/09/learning-japanese-memorization.html) 

The classical method for reviewing items you have already memorized is using flashcards. The basic technique is to create a flashcard with a question on one side of the card and the answer on the other side. Each day, you’d review several cards. For each card, you’d read the question side, try to recall the answer, and then compare your answer with the one written on the backside of the flashcard. However, this method has a major limitation:

After some time, you’ll have a large “database” of several hundred and even thousand cards. It is not practical to review all of them at once. How do you know which cards to review?

Several better techniques have been developed over time. For example, in the 1970s, Sebastien Leitner developed the system now named after him. Using this method, you’d have several numbered decks. Each time you succeed in recalling a flashcard, that card will travel to a deck with a lower priority. On the other hand, if you fail to successfully recall the card, then that card would move to a higher priority deck.

You would now schedule your reviews according to the priorities of the decks. For example. each day you would review cards from the highest priority deck, every other day you’d review cards from the second highest priority deck and so forth. This better optimizes your time - you would spend less time reviewing cards you can easily recall, and more time reviewing cards that are hard for you.

This was no doubt a major improvement. In the computer age, however, we can optimize this method much further. Computer programs which do this are called Spaced Repetition Software (SRS). The first program, of which I’m aware, that pursued this task is SuperMemo.

The basic idea of all the SRS programs are to schedule cards for review at a time in which the review will have an optimal benefit in entrenching the fact in long term memory. When you first learn a card, it is scheduled for review quite often. After each review, the program asks you to **rate **how easy it was for you to recall the fact. Using this data, the program can optimize the time for the next review.

The theory is that the best time to review a card is just when you’re starting to forget it. If you have to sweat a little to recall the card, but you do manage to remember it, then you’ll remember the card for a long time. The idea is to always live on the edge. Never have a feeling that life is easy. As in most things, this gives you great benefits - namely, long term recollection.

I’ve used a couple of SRS programs over the past few months. At first, I used mnemosyne, which is a cross platform, open source program. Overall the program is pretty easy to use and very streamlined. You aren’t presented with too many options, and you can begin using it immediately. It also has many plugins and existing decks which you can download. The downside is that it is not very configurable, which I for one actually like. It was also a pain to install on an old PowerPC mac, but for Intel machines the installation is very easy. Finally, adding audio and graphics to the flash cards is pretty annoying.

After spending around a month away from computers, I found it was very difficult to return to using mnemosyne. This is actually a problem with all SRS programs. The algorithm requires you to use it at constant time intervals for best performance. After using it daily, a month of absence will take many weeks for the algorithm to overcome. That’s why I decide to start fresh and switch to a competitor - Anki.

Anki has very similar features to mnemosyne. It also has many plugins and existing decks. However, it looks much better visually, everything about it can be configured, sound and graphics are a snap to insert and it has mobile and online versions. It can even let you synchronize your decks across multiple computers. As a final bonus, it is updated much more frequently than mnemosyne.

I’ve now been using Anki for a couple of weeks. This is definitely not long enough to get a feel of its scheduling algorithm. It takes many weeks of daily usage before you can start to experience the benefits of any SRS algorithm. From what I can tell, it looks like a really solid program so far, and I’m happy with it.

Further Reading

  1. Learning Japanese - Memorization: the openning article in this series.
  2. Learning Japanese - Vocabulary: shows a nifty plugin for Anki that can really help you learn your vocabulary.
  3. Configurability: what I think of configurability.