Common learning techniques such as re-reading, highlighting, cramming and note-taking are ineffective. So what does work?

Spaced repetition is an evidence-based technique that leverages the spacing effect. It is proven to increase the rate of learning.

“Your memory is a monster; you forget—it doesn't. It simply files things away. It keeps things for you, or hides things from you—and summons them to your recall with will of its own. You think you have a memory; but it has you!”

― John Irving, A Prayer for Owen Meany

What is The Spacing Effect?

It’s commonly known if we want to learn something well, learning it once is insufficient for long-term retention. They always say “practice makes perfect”. However, ‘when’ we practice plays a big role as well. In order to practice effectively, we need to space out our practice.

According to the spacing effect, we learn better when you space out your study sessions. Spaced repetition leverages this effect. You space out your study sessions with increasing intervals between each study session.

Spaced repetition works for numbers, words, images and even skills! To prove this, imagine yourself in a piano class. Practising 10 minutes a day for a week is better compared to practising 70 minutes in one day. According to the spacing effect, you create more long-term memory by spacing out your study sessions compared to cramming.

In a 2006 study, participants did memory tasks. Those using spaced repetition outperformed massed repetition users 259 out of 271 cases.

Discovery of Spaced Repetition

In 1885, Hermann Ebbinghaus memorised thousands of nonsense syllables such as "WID" and "ZOF". He recorded how what he forgot over time and plotted it on a graph. This graph led to the discovery of the Forgetting Curve.

According to this curve, your memory decays over time when you don't review it. When we learn something new, we'll forget half of it by the next day or week unless we review what we learned. However, it is possible to disrupt this forgetting. All we have to do is repeat our review of the information.

According to Ebbinghaus, you can flatten the forgetting curve with each repetition. By spacing your repetitions, you can flatten the forgetting curve and commit everything to memory!

The Science Behind Spaced Repetition

The exact cause of why spaced repetition works are still unknown, but some factors are shown to contribute.

1. According to researchers, repetition over time causes us to form associations between pieces of info. It is easier to recall information when we form associations. This phenomenon is called semantic priming.
2. Our brains prioritise information often repeated compared to information seen once. For instance, we don't have any trouble recalling information we use every day but find it hard to remember the name of an acquaintance.
3. Massed learning is inefficient because we lose interest with each repetition. As a result, we stop focusing on the task at hand. In contrast, spacing our repetition leverages our initial interest before we lose our focus.
4. By spacing our studying, we will forget. Forgetting is a part of learning. When we review what we have forgotten, our brains will reinforce our memory and add new details.
5. By spacing our studies, it's often more challenging for us to recall. When we put in more effort to remember something, the harder it is to forget in the future.

How to Use Spaced Repetition

Here are three ways to create your own spaced repetition system

1. Schedule your review of information. After learning something, go through it again after an hour, then a day, then a week, then every month, then every six months, then yearly. If you can recall the information, move it to the next level and review it less often. If you get it wrong, push it down a level and study it more often.
2. Track your progress. Spaced repetition requires consistency. You need to use positive reinforcement to encourage the habit. Tracking your progress gives us a sense of improvement and progression. Popular options are the Seinfeld method and habit trackers.
3. Set a fixed duration when reviewing. When we practice for too long, we lose our focus and keep less information. A session must be long enough for us to get in the flow, but short enough so we don't lose attention. Start by reviewing for 25 minutes and having a short break of 5 minutes before starting another session. This is called the Pomodoro Technique.

The most popular spaced repetition tools are flashcards and spaced repetition tools such as Anki and RemNote.

Leitner System

The Leitner systems is a method for studying flashcards. In this method, you sort flashcards into boxes according to how well you can recall them.

You start this method by trying to answer the question on the flashcard. If you get it correct, send the card to the next box. If you get it wrong, send the card to the first box. Each succeeding group has a more extended period before you have to review them. Spaced repetition apps like Anki and RemNote does this scheduling for you.

Remembering everything is not about how smart you are, but about how you structure your learning. To get started with spaced repetition, check out my guide on Anki.