Spaced Repetition Systems (or “SRS” for short) are flashcard programs designed to help you systematically learn new information—and retain old information—through intelligent review scheduling. Instead of wasting precious study time on information you already know, SRS apps like Anki allow you to focus most on new words, phrases, kanji, etc., or previously studied information that you have yet to commit to long-term memory.

Why Should You Use Spaced Repetition in Language Learning?

Because We Forget New Information REALLY Quickly Unless Reviewed

In 1885, a German psychologist named Hermann Ebbinghaus (1850-1909) put forth a paper titled “Über das Gedächtnis” (“On Memory”) in which he codified something every school student already knows: New information is forgotten at an exponential rate unless reviewed immediately. He plotted this rate along what he termed the “forgetting curve.”

As you can see, Ebbinghaus observed that he forgot new information almost immediately, with over half of the target information lost in just the first hour! Though his experiment was conducted only on himself (i.e. an N=1 study), his basic findings have been reproduced in more scientific studies since his time, and it’s generally agreed that we forget the vast majority of new information we encounter (as much as 80%) within 24 hours.

Because Spaced Repetition Lets Us Hack the Forgetting Curve

The good news is that we can use strategic repetition schedules to hack our memory and help control what sticks and for how long. Each subsequent re-exposure, if properly timed, can help push information we want to remember further and further into long-term memory.

This memory-boosting method was first popularized in language learning by Paul Pimsleur (1927-1976), the man behind The Pimsleur Approach. His particular brand of spaced repetition was dubbed “Graduated Interval Recall” (GIR), which he detailed in a 1967 paper titled “A Memory Schedule” (published in The Modern Language Journal). His proposed review schedule was as follows:

  • 1st Review: 5 seconds
  • 2nd Review: 25 seconds
  • 3rd Review: 2 minutes
  • 4th Review: 10 minutes
  • 5th Review:  1 hour
  • 6th Review: 5 hours
  • 7th Review: 1 day
  • 8th Review: 5 days
  • 9th Review: 25 days
  • 10th Review: 4 months
  • 11th Review: 2 years

Modern SRS apps and software use even more complex scheduling, but lucky for us, all the math is done automatically by algorithms like SuperMemo’s SM2.

How Spaced Repetition Systems Work

Most SRS apps rely on self-ratings of difficulty to schedule reviews. For example, in Anki (one of the recommended apps I discuss more below), you will usually have 3 or so levels of difficulty to choose from:

  • Red button: Used for “new” or “difficult” cards that you want to be shown again very soon.
  • Green button: Fairly easy or somewhat familiar cards that you want to see again in a little while.
  • Gray: Easy card that you don’t want to review for a while.

The exact interval of minutes, days, or months that each button represents will vary depending on how many times you have previously reviewed the card. For example, if this is your first time seeing a particular card:

  • The red button will probably be labeled “1m” (i.e. 1 minute until the next review).
  • The green button will probably read “10m” (i.e. 10 minutes until the next review).
  • The gray button will probably read “4d” (i.e. 4 days until the next review).

How to Get the Most Out of SRS

Grade Yourself Honestly, But Quickly

A lot of learners get hung up on how to rate themselves, worrying they are giving themselves an overly generous score when they don’t really know the material or being too harsh on themselves when they were close but not perfect. Don’t fall into the trap of spending your valuable time deciding what you know instead of actually expanding what you know. When in doubt, just grade yourself in the middle and move on to the next card.

Use Complete Sentences & Clear Contexts

Avoid creating cards with just a single word or Kanji on the front and the reading or meaning on the back. These are boring and do little more than expand your declarative memory; procedural memory is what we are going for and that is only developed when seeing how words are used in context. Therefore, use complete sentences or even entire paragraphs.

Use Interesting Content

This may seem obvious, but I am constantly surprised by how many learners spend years forcing themselves through boring material. When you are assigned material by a teacher, you may not have a choice, but when learning on your own through Anywhere Immersion, the choice is yours. Read and listen to content that excites you, topics that you would spend time with even in your native language. Then take chunks of this text or audio content you love (but perhaps don’t quite grasp entirely) and put them into your SRS deck.

Don’t be Afraid to Delete Cards

If you come across cards that are too easy, boring, or just annoying, delete them from your deck. Don’t think about it too much. If you find yourself wanting to delete a card but are unsure if you should, just delete it and move on. You won’t miss it. As Khatzumoto of All Japanese All the Time puts it:

“When your SRS deck starts to become more of a chore than a game, bad cards are most likely your problem.”

Recommended SRS Apps & Tools

There are loads and loads of apps available today that incorporate spaced repetition. Here are a few of the best:


Instead of the potentially problematic self-ratings used by most SRS systems, Skritter employs “active recall” (i.e. requiring us to actually write Chinese characters on the screen of our mobile device) to confirm which we know by heart and which we simply recognize but cannot yet produce from memory.



Memrise is arguably the best designed SRS tool on the block, but the site and apps offer much more than just a pretty user interface:

  • Sound science. The entire Memrise experience is designed to optimize memory through the use of “elaborate encoding” (each flashcard includes community-generated mnemonics, etymologies, videos, photos, and example sentences), choreographed testing, and scheduled reminders (i.e. spaced repetition).
  • Fun methodologies. Memrise points out that “we’re at our most receptive when we’re at play.” To that end, they have made efforts to incorporate gaming principles into their system. For example, they use a fun harvest analogy for learning (perhaps taking a page from the FarmVille playbook), breaking the learning process up into three phases: 1) Planting Seeds, 2) Harvesting your “saplings”, and 3) Watering Your Garden.
  • Community. Perhaps the greatest benefit of Memrise is access to community generated “mems” (i.e. mnemonics), including a number of clever animated GIFs for Kanji.



Literally meaning “memorization” in Japanese, “Anki” (暗記) is one of the most popular SRS tools for language learning, and for good reason: 1) it has as heaps of useful user-generated decks, 2) it allows for extensive customization, and 3) it works on every major platform.

As polyglot and Fluent Forever founder Gabriel Wyner puts it:

“Anki is a memorization product that works like a dream. It’s about as close as we’ve gotten to the ‘I know Kung Fu’ scene from The Matrix. In exchange for basically playing a video game for 10-20 minutes a day (or longer, if you wish), you can more or less upload data into your brain, and Anki will take care of getting it deeper and deeper into your long term memory.”

If you’re curious why three of the four platforms are free, while the iOS version costs 25 buckaroos, read Anki creator Damien Elmses’ justification:

“Taken alone, AnkiMobile is expensive for an app. However, AnkiMobile is not a standalone app, but part of an ecosystem, and the $17.50 Apple gives me on each sale goes towards the development of that whole ecosystem. For the price, you get not only the app, but a powerful desktop application, a free online synchronization service, and mobile clients for various platforms.”

Once you install your app of choice, make sure to download some of the shared decks created by other Anki users. There are heaps for most major languages, with lists for reviewing Chinese characters, practicing high-frequency words, etc.


Flashcards Deluxe

A good low-cost, high-quality, user-friendly alternative to Anki is Flashcards Deluxe from Orange or Apple. The app, available on both iOS and Android for $3.99, allows you to either create your own multisided flashcards (complete with audio and photos) or import pre-made decks from and


Japanese Dictionary App

The Japanese dictionary app for iOS and Android gives you the option to study your saved words using spaced repetition. Simply tap “Lists” and then choose one of your bookmark folders to study or tap the 3 dots in the upper right corner and select “Study All These” to review all saved words. As you get more familiar with words, they will move from “Started,” to “Memorized,” to “Learned.” Each day you will see how many cards are due for review in red. Tap this number or “Review” in the upper right corner.


Pleco’s Flashcard Module

The Pleco dictionary app for iOS and Android is by far the most powerful mobile Chinese dictionary available. The basic app and standard dictionary databases are free, but there are a number of paid add-ons to expand its functionality, including an excellent spaced repetition flashcard system for ($9.95).


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