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Spaced Repetition: The Most Universal Learning Technique

Spaced Repetition Overview

Today, our live goes really fast, and the amount of information we have to keep and operate in our everyday lives is truly enormous. And we’ve all gotten used to it already, haven’t we? Heck, we can just ask Google when we need to get some key facts 🙂

But when it comes to passing exams or taking language courses, we need to memorize a lot of data only using our own brain. Your smartphone will be absolutely useless when it’s your time to shine.

So, how could we manage to learn foreign languages, technical terms, historical facts, and other things, and be sure that this learned material will stay in our brain forever? As you might have guessed already, the answer is the Spaced Repetition System.

What is Spaced Repetition System (SRS)?

The Spaced Repetition System (SRS) is an efficient learning technique that has the following concept at its core: when you repeat something over time using specific intervals, your brain is more likely to retain this information rather than forget it. Sounds quite obvious, doesn’t it? 🙂

Here is a science behind this concept. Our brain naturally tends to forget the data it doesn’t need while storing the useful info as closely as possible. But how can we tell our brain what kind of data we want it to remember?

When you initially study some subject and then keep repeating it again and again using SRS intervals (1 day, 7 days, 16 days, etc.), your brain starts to recognize the importance of this material for you (it is also called spacing effect) and decides to keep it rather than forget it. As simple as that!

History of Spaced Repetition

Spaced Repetition System is not a new concept, though. It was developed by the German psychologist Hermann Ebbinghaus back in the 1930s of the 20th century. Yes, almost 100 years ago!

While experimenting with memory retention patterns, he discovered what he called later a “forgetting curve“. He noticed that reviewing information at specific intervals can prevent it from being forgotten.

Ever since, the system has been adopted by numerous scientists and enthusiasts. In the 1970s, Sebastian Leitner introduced his famous Leitner System, which is mostly based on the concepts of the Spaced Repetition System.

How Does it Work?

Forgetting curve

Now, let’s take a closer look at the forgetting curve:

Ebbinghaus's Forgetting Curve

As you can see in the image, the forgetting curve illustrates the relationship between time elapsed and the percentage of information we forget after the initial learning.

It demonstrates that just 20 minutes after acquiring new knowledge, we’ve already forgotten almost 40% of it. Quite impressive, isn’t it? Moreover, as time passes, our memory retention decreases. Our brains seem to believe that if we neither review nor use this information, it’s unnecessary.

With this “forgetting curve” in mind, Ebbinghaus formulated a schedule using specific time intervals. By aligning your study sessions with this schedule and consistently refreshing what you’ve learned, you can prevent the erosion of your knowledge. It’s like giving your memory a tune-up to ensure that the vital information remains securely stored.

Why is Spaced Repetition Effective?

Knowing about the “forgetting curve,” we can now easily answer this question. The Spaced Repetition System is highly effective because it leverages the brain’s natural rhythms of processing and forgetting information.

When we study using repetition intervals, we aren’t forcing our brain to operate at our pace; instead, we’re facilitating a more natural and effective process of remembering.

As long as we continue to stick to the schedule and repeatedly refresh newly acquired knowledge, our brain naturally embeds it deeply and prevents forgetting.

As we can see, there’s no magic here – just efficient cooperation with our brain. That’s what makes Spaced Repetition so effective.

Algorithms and Time Intervals

Although the core concepts of Spaced Repetition System remain unchanged – reviewing learned materials over specific time intervals, the system proved to be highly adoptable for different learning styles and tools.

Since it initially appeared in the 1930s, many variations were developed ever since, especially in the last few decades. So, let’s now consider the most popular ones below.

SuperMemo Algorithm

The SuperMemo Algorithm was first introduced in 1985 by Piotr Woźniak, a Polish researcher. Based on the idea of the Spaced Repetition System, it was modified and implemented as a part of learning software for Windows.

The algorithm has evolved over time. Starting from the initial version SM-0, improved modifications from SM-2 (the most popular) to SM-18 were released.

The key feature of the SuperMemo algorithm is that it takes into account the difficulty of the learning materials. Thus, more challenging pieces are reviewed more frequently, while easy-to-learn materials have longer intervals for reviewing, saving valuable time for learners.

Leitner System

Way back in 1972, even before Piotr Woźniak began his research, another talented enthusiast from Germany, Sebastian Leitner, introduced his version of the Spaced Repetition System. It was named after him – the Leitner System.

The key concept of the Leitner system involves using 5 boxes with flashcards. Each box represents a different difficulty level for the learning materials: from the initial 1st level (just learned) to the 5th level (strong knowledge). Using the Leitner Schedule (a variation of Spaced Repetition intervals), learners review flashcards and move them between different boxes based on whether they remember the material or not.

As one of the most popular implementations of the Spaced Repetition concept, the Leitner system was later incorporated into various computer software and mobile applications, such as “Leitner Box.”

Anki Algorithm

Another popular implementation of the spaced repetition idea is the Anki algorithm. What’s interesting is that it is based on Piotr Woźniak’s SuperMemo algorithm and modified to better fit Anki memorization software.

Similar to the Leitner System, the Anki algorithm involves the use of various decks with cards, where studied materials are placed. As learners progress with these cards and demonstrate a good grasp of the material, they are reviewed less frequently.

In general, all three algorithms we discussed above share the same idea of the Spaced Repetition System: learning materials are divided into small chunks (cards) and reviewed according to a specific schedule to prevent forgetting.

How to Get Started?

By this moment, you should have all the information you need to start practicing Spaced Repetition. Now, let’s review the exact steps that will help you begin your learning journey.

In general, to be successful in everything you do in your life (not only in learning), you need to set clear goals for what you want to achieve. So, before creating any flashcards or selecting a learning schedule, write down the following key points:

  • What exactly are you going to learn? Is it 100 or 1000 foreign language words, key facts about some historic period, or a set of specific technical terms?
  • How do you plan to apply what you’ll learn? Knowing your real use cases is important because it will help you create effective and personalized flashcards.
  • Do you have any deadlines to consider (e.g., an examination date), or can you study your material at a more relaxed pace?

After setting your learning goals, review them carefully, and let’s move to the next step.

Knowing your learning goals will help you select appropriate tools. Ask yourself the following questions:

  • Do you want to use digital tools (applications), or would you prefer trying physical cards and boxes?
  • If you prefer using an application, will it be a mobile app or desktop software?
  • In case you are going to use physical stuff, will you buy ready-made sets, or do you want to craft cards and boxes yourself?

In most cases, we recommend using a mobile application because it’s more practical nowadays: you can learn anywhere you want, you don’t need to buy or create physical stuff, you’ll have the ability to save and track your progress, and much more.

Next, you need to choose the SRS algorithm to use. As we discussed above, being very similar, they have their nuances though. For beginners, it’s easy to recommend starting with the Leitner System because of its simplicity and flexibility.

Creating effective flashcards is arguably the most important preparation step. Depending on the effectiveness of your flashcards, you will either achieve your goals quickly or potentially encounter difficulties along the way.

No matter which Spaced Repetition algorithm you use or what material you study, these universal rules will help you create efficient cards:

  • Split your material into small pieces. Avoid overloading one card with too much information. Simplicity is your friend.
  • Utilize context (see Setting Goals above). For learning foreign words, consider including sentences where the word is used. For terms or key facts, add explanatory context.
  • Incorporate images whenever possible. Visual elements help your brain establish more robust mental connections with the material.
  • Organize cards into different sets (or boxes) based on material type. For instance, have one set for exact words or terms and another for explaining language rules or mathematical theorems.

After creating several cards, review them and take note of any challenges or difficulties you encounter. If you find that certain cards are hard to work with or remember, recreate them. It will save you a bunch of time during your study sessions.

Over time, your study sessions will start bringing their first results, and it will be satisfying to realize how much you’ve learned since the beginning. You’ll gradually move well-known cards higher and higher between boxes, increasing their proficiency level.

But there’s a chance you may encounter some challenges too. For example, you might get stuck on certain cards, struggling to remember the material repeatedly. Or one day, you’ll realize that some of your boxes are already too overcrowded. No need to worry – it’s absolutely normal.

But what’s important here is to make small adjustments as you progress:

  • If you encounter any challenges with some of your cards – try to recreate them.
    In case some of your boxes contain too many cards and it’s uncomfortable for you to learn them anymore, consider redistributing these cards into different boxes. For example, you can split cards by subtopics.
  • The efficiency of the Spaced Repetition System truly shines only when you stick to your learning schedule. If you find yourself with a substantial amount of material to cover each day but regularly skip study sessions due to time constraints, it’s a good idea to reduce the number of cards you are learning. Remember, it’s much better to dedicate 10 minutes a day consistently than 30 minutes a day with intermittent gaps.

Usage Examples

Thanks to the versatility and flexibility of the Spaced Repetition System, it can be successfully used for studying a wide range of different topics. From language learning to math formulas, from music notes to medical terminology – everything can be divided into small pieces and placed on flashcards.

Let’s consider several possible scenarios below.

Studying Geographic Facts

Geography is a topic that contains a huge number of different facts. Just to name a few:

• Continents and their countries;
• Countries and their capitals;
• Population numbers;
• Major seas and rivers in a region, and so on.

SRS is an ideal system for studying Geography. You can create distinct boxes for studying capitals, rivers, the largest cities in various countries, and more. Additionally, you can boost your learning experience by adding images to your flashcards, such as pictures of cities or prominent symbols representing countries.

Memorizing Medical Terminology and Anatomy

When it comes to extensive terminology and specialized jargon, medicine can outmatch most other fields of knowledge. It can also explain why doctors spend so many years studying and then usually have bread and butter on their tables 🙂

If you are studying medicine or preparing for exams, the Spaced Repetition System can provide you with a significant advantage. You can include the following data on your flashcards:

• Various medical terminology, from basic terms to advanced namings. You can organize your data into different boxes to prevent clutter.
• Anatomical knowledge, including the names of human bones, organs, muscles, blood vessels, and more. You can even enhance “anatomical” cards with images to improve learning efficiency.
• Information about different deceases: basic symptoms, etiology, treatment options, etc.
• Infinite medical abbreviations and acronyms, which are usually used in daily practice (like IDDM, ADR, HAPE, and others).

These examples are just the tip of the iceberg. With SRS, you can successfully study medical guidelines and case studies, histology and pharmacology, numerous medical procedures, and much more.

Remembering Chemical Elements

If you’ve studied chemistry at school, you know that Mendeleev’s periodic table plays the leading role in this field of knowledge. However, memorizing data about all 60+ elements can be extremely challenging. So, as you may have guessed already, this is a perfect case for the Spaced Repetition System.

You can create the cards for each chemical element and include the following data:
• Element name, such as “Hydrogen” or “Oxygen.
• Element symbol, like “H” for hydrogen or “O” for oxygen.
• Atomic number: A unique whole number based on the number of protons in its nucleus.
• Atomic mass of the element’s isotopes, in atomic mass units (amu) or unified atomic mass units (u).
• Electron configuration – how electrons are distributed in the electron shells or energy levels of the element’s atoms, and so on.

For better memorization, you can create different sets of flashcards for each single characteristic, like cards with only atomic mass or element symbol.

In any case, whichever approach you choose, the Spaced Repetition system can become your best mate in studying chemistry and save you a lot of time.

Combine SRS with Other Learning Methods

Without a doubt, the Spaced Repetition System is a very powerful tool by itself. But, who told you can’t make your learning process even more effective? Let’s see what we can improve here.

Our brain memorizes information in the following scenarios:
When you read the material first. The retention rate is very low in that case.
When you see or hear this material once again. Things are getting better.
When you repeat the pieces of the material over time. Yes, that’s a Spaced Repetition system, and your retention rate is already much higher here.
When you speak out loud during spaced repetition sessions. Verbal confirmation establishes additional neural connections in your brain.
When you write down the pieces of material by hand. As with speaking, this kind of activity also proved to work very well for memorizing.
When you read the whole material in the context after the SRS session. For example, you are reading a chapter of a history textbook just after studying flashcards with the history facts from this chapter.
When you retell someone what you’ve just learned. In that case, you reinforce your new knowledge one more time.

Okay, but how can we combine all these methods into a coherent learning process? Here is a sample workflow:

In the steps above, we are employing various complementary methods to boost the effectiveness of the Spaced Repetition System. We read, write by hand, repeat the material, read it in context, and finally, we retell it out loud.

Yes, it can be time-consuming, but do you think your brain has any chance of forgetting what you’ve learned now? We highly doubt it.

Spaced Repetition Apps

Using spaced repetition applications has many advantages compared to the old-fashioned physical cards and boxes.

Firstly, you can learn whenever you want: at home, in bed, at school or university, during your commute to work, or even on vacation if you’re determined enough 🙂

Secondly, you can save a lot of time creating cards. It’s much faster and easier to add digital flashcards to the virtual box than to create (or fill in) physical ones.

Thirdly, you don’t need to worry about storing your cards and boxes. It’s not a problem if you have one or two boxes, but it can be quite tricky to keep 5 to 10 boxes filled with multiple cards.

Finally, you don’t need to bother about learning schedules and repetition intervals – all spaced repetition apps will handle it for you. Moreover, good apps even have built-in reminders, so you’ll never forget about your learning sessions.

There are a number of spaced repetition apps to choose from. You can find some apps worth considering in this article.

Useful Tips

Now, that you are already aware of Spaced Repetition principles, workflows, and tools, let’s discuss how you can make your learning even more effective.

Depending on the specific algorithm, you are expected to review your high-level cards, on average, once or twice a month. This gives you a time frame of at least several months to confidently study new material.

Try implementing all or some of these tips and tricks, and analyze the results you have achieved. Have you improved your retention rate? Did you manage to memorize your cards more quickly? Congratulations, you are on your way to mastering the Spaced Repetition system!


Spaced Repetition System is a learning technique that involves reviewing and repeating information at increasing intervals over time to enhance long-term retention.

You create flashcards and place them into different boxes depending on the topic. Then, you review the flashcards at specific intervals to prevent forgetting the material and move them between boxes as your confidence level increases.

SRS helps improve memory retention, reduces study time, and elevates learning efficiency. It’s particularly effective for long-term recall of facts, languages, and complex subjects.

Absolutely! SRS is highly customizable and adaptable, making it suitable for various subjects, including language learning, science, history, math, medicine, geography, music theory, and much more.

Buying or crafting flashcards and boxes can be an exciting experience in itself. However, utilizing Spaced Repetition System software, such as desktop or mobile apps, can save you a lot of time and enable you to review your cards whenever you prefer.

Effective flashcards should be concise, focused on a single concept, and include clear questions or prompts. Adding images or context can also enhance memorization.

The review schedule in SRS typically start with shorter intervals (e.g., hours or days) and gradually extend over time. The exact intervals may vary based on the system and your progress. For example, the Leitner Box mobile app has a built-in learning schedule, so you don’t need to worry about it.

Yes, SRS can complement other techniques like active recall, note-taking, or group study. Combining SRS with different approaches can significantly enhance your overall learning experience.

If you’re looking for rapid memorization, other techniques like cramming might seem more effective in the short term, but they often lead to quick forgetting. SRS is about sustainable and lasting knowledge acquisition, so it might not be the best choice for those seeking rapid recall within a very short timeframe.

Final Thoughts

You’ve reached the end of this tutorial — congratulations! Should we summarize everything you’ve learned here? Let’s go!

Firstly, now you know that the Spaced Repetition System is very versatile and can help you remember almost any type of material. Just break it into concise chunks and put it on the flashcards.

You also know that SRS is especially effective in the long run when you need to remember your material for an extended period. Leveraging the principles of the Forgetting Curve, the Spaced Repetition System won’t let you forget what you’ve learned.

And, finally, you understand that effective learning using the Spaced Repetition System requires time, patience, and discipline. SRS will only work if you follow your learning schedule and review flashcards exactly when needed.

Ready to give it a chance? Don’t wait any longer, and good luck!

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