Spaced Repetition 101: What Is It And Why Does It Work?
Why you should use Anki or another SRS program.
In previous posts, I have often referred to spaced repetition, Anki, and Spaced Repetition Software (SRS).
For anyone that doesn’t already know these terms, I thought it would be useful to give an overview of what they are and how you can use them to optimize your learning process.
Spaced Repetition in a Nutshell
Put simply, spaced repetition is a way of learning things by reviewing them repeatedly over a period of time. This process happens naturally in real life.
For example, let’s say you work in an office building. One day, your boss tells you to take a document up to Room 14A on the 20th floor. Having never been there before, you get lost and you can’t find the room. So, you ask someone and they tell you that Room 14A is actually not next to Room 14, but is near Conference Room A. After some more searching, you find the correct room.
A week later, your boss assigns you the same task: take a document up to Room 14A on the 20th floor. This time, however, you’re familiar with the route. Although you don’t remember every precise detail, you do remember the Room 14A is near Conference Room A, which is to the left of the elevator.
A few weeks later, you get the same task. Now that you’ve been there twice before in the past month, you know exactly where to go. As you’re waiting for the elevator back to your floor, someone asks you where Room 14A is. You’re an expert now, so you tell him the precise directions: “left, first right, second left, third door on the left, across from Conference Room A.”
A decade later, you’re a vice president at the company. There’s a big meeting tomorrow in Room 14A. Even though you haven’t been there in years, you still remember how to get there reasonably well.
The Spacing Effect
This is fundamentally how spaced repetition works: by being presented with the same piece of information over progressively-increasing intervals of time, it becomes easier to remember. This is because of the spacing effect:
The spacing effect demonstrates that learning is more effective when study sessions are spaced out. This effect shows that more information is encoded into long-term memory by spaced study sessions, also known as spaced repetition or spaced presentation, than by massed presentation ("cramming").
This means that it’s actually more efficient to review something infrequently than it is to review it all at once.
The Research
The spacing effect has been studied extensively over the last century and has significant scientific evidence. Hermann Ebbinghaus first detailed it in his 1885 book, Memory: A Contribution to Experimental Psychology. Dozens of other studies have been done since, confirming the effect.
In this post, I won’t delve too much into the research as to why spaced repetition works. For now, you can read about it in the Wikipedia article or in this article by SuperMemo.
The short version is this: by increasing the amount of time between review sessions (1 day, 2 days, 4 days, 8 days, etc.) you increase the difficulty of retrieving that information. Because it is more difficult, your brain considers it more important and uses more resources putting it in your long-term memory. Thus, you remember it better.
Notecards and Real-World Use Cases
But how can you use this for learning specific things? With flashcards. As mentioned in the Wikipedia article, spaced repetition is used primarily in conjunction with flashcards and flashcard software.
This is because flashcards lend themselves well to reviewing small pieces of information. The Leitner System, for example, is a very simple way to use spaced repetition with physical flashcards.
There are different variations of it, but it basically works like this:
All cards start in Box 1. When you review a card and know the answer, you move it to the next box. If you don’t know the answer, it goes back to box 1.
The number on the box indicates how often you review the cards in that box. For example:
Box 1 means you review those cards every day
Box 2 means you review those cards every 2 days
Box 3 means you review those cards every 3 days
Eventually, all of your cards should end up in Box 3, where you’ll review them every 3 days – and remember the information on them quite well.
All spaced repetition systems have the same type of design, although software programs use a complex algorithm that is more optimized for your memory. Ideally, you will review the information just as your brain is about to forget it.
But what can you learn with spaced repetition? Pretty much anything, although it works better for discrete facts and other pieces of information. Common use cases are foreign languages, medical school courses, history, geography, chemistry, mathematical formulas, programming language syntax, biology, and lines of poetry.
Anki and Other Spaced Repetition Software
While you can create a simple spaced repetition system using flashcards, these days, most people use a software program. There are many options available, but one of most popular Spaced Repetition Software (SRS) tools is Anki.
Put simply, Anki cards are digital versions of flashcards. You can add images, audio, text, and other information to digital “cards” and then review those cards according to the Spaced Repetition schedule we mentioned above.
While Anki isn’t as intuitive to use as physical flashcards, it makes up for it by being far more efficient – and by implementing a more complex algorithm that helps you maximize your memory while minimizing time spent reviewing.
Although Anki has a rather bland design and a steep learning curve, it is an incredibly powerful tool and allows for an extensive amount of customization.
I’ll cover the ins-and-outs of Anki in future posts, but if you’re looking to get started, I recommend these tutorials: