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Tag: spaced repetition

What is a spaced repetition system? What is it useful for? What are its limitations for use in language learning? See this two minute video.

Anki is a free software program designed to help people remember what they have learned.anki-logo It’s a flashcard program, with support for a variety of media, including text, sound files, mathematical equations (using Latex) and even images. My use of it so far has been restricted to foreign language learning. Anki runs on Windows, Mac OSX, and Linux.

The value of spaced repetitions

Anki is a spaced repetition learning system. Unlike traditional flash card systems in which the user decided what to practice and when, spaced repetition systems schedule practice for you. The first time someone learns something, it will be forgotten quickly. The next time, it might stay for a day or two. The time after that, a learner can usually remember an item for over a week. The length of time increases exponentially. If an item is forgotten, though, much of the progress is lost. By scheduling review for each item right before the learner is expected to forget it, Anki makes it possible to learn material well enough to remember it for months or even years in just ten to twenty repetitions.

My own learning experiences have made me a big fan of spaced repetition review. I have been a reasonably hard-working student ever since my last stint in college, but a depressing amount of the work was wasted. I have entire notebooks full of things I’ve painstakingly learned, probably reviewed more often in the early stages and then forgotten because failed to go over them months later. As much as I like the idea of deciding when and what to review, following the algorithm is more effective.

Differences from Supermemo

As far as the algorithm is concerned, Anki is very similar to SM2. When answering correctly, you still get three options (easy, good and hard), but there is only one option for wrong answers. Anything you answer wrong is put back into the stack, to be reviewed after you finish your other cards for the day. One very good change is that wrong answers don’t really affect the card’s “difficulty rating” before you’ve really learned a card well, i.e. to the point at which you have about a month between intervals. In other words, you won’t keep seeing a card too often a year from now just because you hadn’t really learned it before putting it into your deck.

The biggest way Anki is different from Supermemo is the clean interface. It’s a nice, simple program and it’s a joy to use. You can also copy decks to the Anki site for free (up to 10MB), and sync decks after you finish with them so that you can review from other computers. This isn’t a very important feature for me, but it would be if I had a decent cellphone.

Other features

Anki has some specific features for learners of Chinese and even more features for learners of Japanese. There are “deck models” for both languages. Each card has a field for the “question” (the word), the “answer” (the English translation) and a special third field for the reading. Upon entering a Chinese word, Anki fills in the pinyin for you! For example, if I enter the word 嫻靜, Anki fills in xián jìng for me. This is a great time saver. Unfortunately, it’s still necessary to choose the right pronunciation in the case of 破音字. The recognition for Japanese characters is far better. Anki has automatically selected the correct hiragana for the vast majority of the Japanese words and phrases I’ve entered so far. It’s a good thing, too. Otherwise, it would be necessary to choose from half a dozen readings on a regular basis. On other feature for Japanese study is that the program tracks how many of the Jouyou and Jinmeiyou Kanji have appeared in your deck so far. It also tells you what percentage of the kanji for each grade of elementary school you have learned.

Graphs and Statistics

Anki’s charts and statistics are outstanding.ankichart You can see charts of when cards will be up for review, of how much time you’ve studied each day, of how hard your cards are for you, and all kinds of other things. Deck statistics are similarly impressive. Have you ever what percentage of the time you answer correctly on cards you’ve been studying for a long time? Or what percentage you get right in your first review session? Anki can tell you. In fact, the charts and statistics might be a little bit too good. I’ve found myself checking them more than I really want to.


Anki is free software. As a proud free culture supporting geek, this makes me very happy. On the practical side, it also leads to cross-platform support and it’s easy to extend Anki. In fact, I’ve taken advantage of this by getting the Traditional Chinese localization of the program started. Damien, the original author and maintainer, was very helpful via email explaining to me how to edit the localization files. I’m sure others, with native Chinese skills, will build upon that work. If enough Chinese students get interested in Anki, I bet it will start keeping Hanzi statistics, too. By virtue of its license Anki is certain to keep improving for as long as it’s popular.


Anki is great. I’ve been using it daily for most of this month and I’ve even put in some time localizing it so that I could give it to one of my students. He’s been hard working, but continues to struggle to build his vocabulary. I’ve put all the vocabulary from my first semester CDs into Anki decks for him and have high hopes. I wouldn’t be using it myself and I certainly wouldn’t be recommending it to my students if I didn’t think Anki was the best of its breed.

Rating: 4.5/5

I’ve had a passing interest in the concept of spaced repetition ever since I read the Wired article about Piotr Wozniak’s fantastic human experiment.

Twenty years ago, Wozniak realized that computers could easily calculate the moment of forgetting if he could discover the right algorithm. SuperMemo is the result of his research. It predicts the future state of a person’s memory and schedules information reviews at the optimal time. The effect is striking. Users can seal huge quantities of vocabulary into their brains. But for Wozniak, 46, helping people learn a foreign language fast is just the tiniest part of his goal. As we plan the days, weeks, even years of our lives, he would have us rely not merely on our traditional sources of self-knowledge — introspection, intuition, and conscious thought — but also on something new: predictions about ourselves encoded in machines.

Given the chance to observe our behaviors, computers can run simulations, modeling different versions of our path through the world. By tuning these models for top performance, computers will give us rules to live by. They will be able to tell us when to wake, sleep, learn, and exercise; they will cue us to remember what we’ve read, help us track whom we’ve met, and remind us of our goals. Computers, in Wozniak’s scheme, will increase our intellectual capacity and enhance our rational self-control.

The reason the inventor of SuperMemo pursues extreme anonymity, asking me to conceal his exact location and shunning even casual recognition by users of his software, is not because he’s paranoid or a misanthrope but because he wants to avoid random interruptions to a long-running experiment he’s conducting on himself. Wozniak is a kind of algorithmic man. He’s exploring what it’s like to live in strict obedience to reason. On first encounter, he appears to be one of the happiest people I’ve ever met.

It was a long but thoroughly engaging piece that inspired me to try out Piotr’s software Supermemo. At that time, it never really stuck. I found the interface frustrating, and I wasn’t really interested in buying the full product. At the time, my motivation to study Chinese was on the ebb anyway.

Recently, spaced repetition has come back onto my radar, thanks to what John’s writing about his study of classical Chinese.

In fact it’s motivated me enough to not only give it a try for my own study, but I’ve decided to try to contribute to an open source spaced repetition program, Anki, over the Chinese New Year. The interface is great, it’s easy to use and I love it. I’ll definitely be writing more about it soon.

The program is fully free (gratis and libre), and I can see it as not only helping me with my studies, but with a bit of localization it can also help my students and other students as well. Maybe not being able to get a plane for a visit home wasn’t such a bad thing after all.

If anybody is interested in helping me translate the Anki interface into traditional Chinese, I’d love to have your help. I’m only a small way through and there are still about 6000 lines of messages left to go through. I’m not exactly a real translator either.