If your a student, you may have heard of a piece of software called Anki. Anki is one of the two big SRS programs out there right now.

In this post, I will try explain what SRS is to those unfamiliar with it and why it can be a really powerful tool for learning pretty much anything.

SRS stands for spaced repetition software. Spaced repetition is a study technique where you “space out” your repetition of the material over time, with the intervals getting larger with every repetition.

So, what’s the big deal about that, you ask? Well, spaced repetition is one of the most (if not the most) efficient ways to study. I will explain why.

Our brains forget information following a specific pattern called the forgetting curve. Basically, we forget things gradually, with the percentage of the information retained exponentially becoming less and less. The more repetitions of something we do, the slower this decline becomes. This is why if you do something over and over again, you remember it for longer.

The most important and most overlooked stage of the learning process is actually forgetting. This is due to something called the effort principle, which just means that the more effort you have to go through to learn something, the better your mind will retain it.

The goal behind spaced repetition is that you review something right before you are about to forget it. This lets your mind go through the maximum possible effort to remember what you are studying. This way, you will save time as you will do the least repetitions of the material but still retain the most possible information.

If the interval between reviews of the material is too short, then you are wasting too much time with unneeded repetitions because you will not have had the chance to forget some of the material before reviewing it again.

On the other hand, if your intervals are too long, you will have already forgotten the material and may not be able to recall it without looking at some external reference. You will then have to spend time relearning the material which will take up too much time.

This may seem like a small nuance, but think of how this will compound with every single piece of information you need to know for an exam, or with 500+ flashcards (if you take 10 extra seconds to memorize every card, that adds up to around 83 minutes extra added with the time it takes to review the cards themselves)

The easiest way to implement spaced repetition is with flashcards: Physical flashcards, and software methods.

With physical flashcards you can use the Leitner system. The idea is to group your flashcards (with boxes or some other way) into groups based on the time they will be reviewed. Have one box due for 10 min or so, another for the next day, another for three days, a week, a month, and so on. You can customize these intervals to your liking. If you get a card right, move it up one group to the next longest interval. If you get a card wrong, move it down one group.

There are two major well-known software based methods of implementing spaced repetition: Anki and Supermemo. These are both based off of a tried and tested computer algorithm which tries to match your brain’s ability to remember things. Anki is open source, and has a wealth of extensions, pre-made decks, and a large community. If there is something you want to do in Anki, chances are there is probably a way to do it. Supermemo is closed source and has a supposedly more advanced version of algorithm than Anki. For privacy and open source geeks like me, Anki is the clear winner. And you can do everything you can do in Supermemo (plus more) in Anki (except for the algorithm).

I will talk more about how Anki works and how to use it in future posts. This post was just meant as a introduction to spaced repetition and why it is so efficient. Before I heard about it, I would struggle for hours trying to memorize a couple terms. Now I can do a whole semesters worth of terms with just 10 min a day doing my Anki cards. Spaced repetition is also not just limited to academic uses. I use Anki to learn languages, memorize common programming stuff, and for fun as well. For example, I memorized the NATO phonetic alphabet and all the elements of the periodic table with their respective atomic numbers, and am currently going through all the capitals, flags, and maps of every country.

I hope that this was a good introduction to spaced repetition and the various ways to implement it. It can truly be a really powerful way to learn new information.