Spaced Learning: How to Memorize Vocabulary You’ll Remember Forever

Let’s take a moment to acknowledge the obvious: learning first 1000 words in another language takes way too long.

Memorizing these first 1000 words is “eating the frog” analogy1 applied to language learning. The bad news is that you have to “eat” it. The good news: it is the worst (read: the most boring) thing that would ever happen to you on your way to fluency. Once it is done, you will be able to acquire vocabulary naturally, through incidental learning.

“To completely learn something, we must be able to use it repeatedly and independently“, – explains Pierce Howard, the author of “The Owner’s Manual For The Brain” (which is my personal go-to how-to book on almost every occasion).

This general principle extends to language learning. But before you can use foreign language words repeatedly and independently – while reading your favorite novel in Spanish, listening to an energizing podcast in French or chatting with a perfect stranger in Italian – you have to go through the ordeal of memorizing your first vocabulary.

In the previous post, I explained what words you want to focus on to reach basic proficiency level as fast as possible. In this article, you will learn how to memorize this vocabulary most efficiently: with spaced repetition.

Spaced learning 101: Introduction

In 1885, German psychologist Hermann Ebbinghaus came up with the most frustrating line ever drawn in the history of humankind: the forgetting curve.

The Ebbinghaus forgetting curve in all its splendour. Now you know why it's so hard to memorize vocabulary long-term.
The Ebbinghaus forgetting curve in all its splendour.

According to his calculations, 60% of what we learn quickly fades out from our memory within the first few days. And this is why you can’t recall a good half of the vocabulary you learned just yesterday. It would be great to overcome this natural limitation, wouldn’t it?

And there is a way.

In 1932, British psychologist C. A. Mace in his “The psychology of study” modestly suggested that repetitive study over intervals of 1 day, 2 days, 4 days, 8 days and so on would result in more robust learning. A new killing technique, called spaced learning (or spaced repetition), was born.

As various psychologists and cognitive researchers tried to tackle the problem, the method evolved. But the core principle remained the same. In order to memorize something long-term, you need to systematically refresh it in your memory over time. Right spacing intervals ensure efficiency and allow you to focus your efforts on reviewing the information that just about to get lost in the back of your mind.

Spaced repetition is a highly effective method for memorizing – and remembering – large quantities of information: facts, dates, names… and, of course, vocabulary.

It allows you to distribute your efforts over time and learn a boatload of foreign words without reaching the burnout point at any single day. Plus, correctly spaced recall sessions prevent your brain from disposing “not-in-use” vocabulary to a brain dumpster, as you systematically reactivate every word.

As a result, you reach a nice balance between learning new vocabulary and not forgetting words already mastered.

Hacking memory with spaced learning

Simply speaking, spaced learning is a way to “study smarter, not harder”. Spaced repetition exploits the brain’s multiple quirks to upgrade the brain’s very capacity for encoding and retaining information.

There are three major reasons this method is so brain-friendly:

Spacing effect

If you ever tried to cram physics textbook the night before the exam (I did), you probably went through all the stages of despair during the exam. Clearly, a single-session mass repetition doesn’t do the job. Studying over a week with shorter spaced learning sessions, however, leads to success.

The more that people study and review, the more they remember“, notes Pierce Howard in already familiar to you The Owner’s Manual for the Brain. He cites a revealing linguistic study. Students who took five courses of Spanish still remember 60% of vocabulary even after 25 years. Those who took just one, hardly remember anything. Why would it be so?

Here is the harsh truth.

Most of us disengage from any language learning activities once we complete a language course. So nature takes on, and the brain archives whatever it can. You forget. But taking another Spanish course forces your brain to recover this nearly lost information. And here comes a memory trick: this bouncing from forgetting to recalling strengthens neuron connections and makes memory trace more durable, which leads to long-term retention.

The more times you repeat this cycle, the better you memorize vocabulary. There is no need to take five years of Spanish, however. Spaced learning produces the same effect without emptying your savings account.

Retrieval effort

The more time lapses since the last time you saw strapiombo (which is an Italian word for precipice), the less likely you are to recall what a heck it means. However, if you finally get to the Aha moment, your brain will do everything possible to find more associations with this word. It will use these new cues to help you with recalling strapiombo faster for the next time.

As a general rule, the more time you allow between each spaced repetition session the more effortful will be the recall. Painful recall sessions force the brain to reassess the importance of each vocabulary word and lead to deeper semantic processing (if you successfully recall it, of course).2 And here comes the next point.

Retrieval success

Memrise would test how well you remember a new word immediately after they taught it to you. Pimsleur Language Program allows 5 seconds gap between learning and the first recall. With expanding spaced learning, the first recall session typically happens shortly after the learning session. And for a good reason.

Multiple studies have found that once a word was successfully recalled for the first time, people have no problem doing it again and again. The brain seems to remember the successful retrieval, and use it as another cue for recall.

Spacing enhances learning and memory; it is a proven scientific fact. But what spacing intervals are best for long-term retention is a whole another question.

Selecting the most effective spaced learning interval

In the far 1978, two researchers from UCLA launched the first spaced learning training for a group of psychology students from the University of Illinois.3 They explored the effectiveness of different spacing intervals and came to very intriguing conclusions.

There are two major ways to space your vocabulary learning sessions, each with its own unique effect on memory. They are:

  • Uniform intervals
  • Expanding intervals

Uniform VS expanding spacing intervals

The example of spaced learning with uniform intervals would be reviewing your old Spanish vocabulary every 5 days, no matter how many times you already did it. With expanding intervals, on the other hand, you would allow 1 day between the 1st and 2nd sessions, 3 days between the 2nd and 3rd, 5 days between 3rd and 4th, and so on.

Both strategies are more effective than mass learning, but that’s where any similarity ends.

Uniform intervals work best with repetition type sessions and promote long term retention. Expanding intervals go well with test type sessions and are better for short term retention.

Theoretically, uniform spaced learning is how you memorize vocabulary words that you would remember forever. Expanding spaced learning, on the other hand, works best when you prepare for a language proficiency test and want to cover as much of “Must-have TOEFL vocabulary” as possible. Since half of the test-specific words will be completely useless once you’re done, it’s fine to let them transform into a passive vocabulary.

Deadline matters

As a rule of thumb, the optimal selection of spaced learning intervals depends on how long you wish to remember your vocabulary.4

The further away is your deadline (a language proficiency test, for example), the more time you want to allow before the first review session. So if your test is a month away, schedule your first repetition session in a week. If you have just one week to prepare, review your vocabulary one or two days after you learned it.

I recommend going through at least three recalls before the test.

The spacing of these intermediate learning sessions, however, doesn’t seem to affect your brain’s capacity to store foreign language vocabulary to a large extent. As long as you allow enough time between each, your brain won’t have any problem memorizing new vocabulary. 5

So if you wonder how to memorize vocabulary using spaced learning, this should give you a great deal of relief. Deadline is the only thing you need to set up your own SRS.

Using SRS (spaced repetition system) to memorize vocabulary

SRS is a system that determines the intervals after which you have to review vocabulary. There are two approaches to that: analog and digital.

The very first spaced repetition system was fully analog. Created by German science journalist Sebastian Leitner, Leitner System used five boxes with – that’s right – good old flashcards. Initially, you put all flashcards in box #1. If you successfully recalled information from a flashcard, it moved to the next box; if not – it remains in the first one. All boxes had different sizes, so you reviewed the content of each box only once it got full. If you failed to recall the flashcard from any of the boxes – you sent it back to square one.

I wouldn’t create 1000 flashcards to memorize vocabulary, however. Just on principle. Because I’m lazy.

I use flashcards for something else: internalizing rules of grammar and memorizing principles of cognates formation. There is no digital shortcut to understanding the mechanics of language, so my hand-made analog SRS remains the only solution.

Most spaced repetition systems for vocabulary learning, however, turned digital. (It is the 21st century, after all). Instead of boxes that govern the repetition cycle, we now have fully automated scheduling algorithms. And nowadays, every vocabulary learning app uses SRS, some better than the others.

Digital vs Analog Spaced Learning Systems

The beauty of a digital SRS is that you don’t have to scrutinize your spacing schedule to reach the optimal performance. It has already been done for you by developers of your language learning software.

You can’t go wrong using the top software like Memrise, Duolingo, and Pimsleur. However, in this case, you’re giving up a great deal of control over what words you learn and how often you review them.

To tailor your SRS to your own needs, you can choose using open-source platforms, such as Anki and Mnemosyne. It can be a great way to learn target vocabulary, provided you put enough time into creating personalized flashcards.

It is worth to note, though, that both Anki and Mnemosyne are based on SM-2, which is a scheduling algorithm created by Piotr Wozniak and his team. Leaving a working algorithm in the open may seem like an act of goodwill, but these guys have had something better: SuperMemo, a winning SRS learning platform. And currently, SuperMemo itself runs on SM-18, a fine-tuned version released in early 2019.

By now, SuperMemo has one of the most accurate spaced learning algorithms based on years of trials and memory research. They don’t offer 1000+ language courses like Duolingo, but there is a 95% chance that you’d find one for your target language.

Unless you’re learning Inuktitut, of course. In this case, Anki it is.


A proven way to find the optimal spaced repetition system to memorize vocabulary is to explore different options and test how well they work in your case. Take your time to find the best fit and you will save yourself kilowatts of mental energy, months of time and hundreds of dollars.

Image Credits: Photo by Dmitry Ratushny on Unsplash

Author Details
Polyglot, Author and Founder of Linguapath
Hey! I am Alina Kuimova, and my long-lasting obsession with learning languages led to creation of this site. Apart from being a grammar enthousiast, I enjoy reading smart books in any language available, finding easier ways for the brain to learn things and buffing productivity stats by 180%.
  1. Mark Twain once remarked that “If it’s your job to eat a frog, it’s best to do it first thing in the morning. And If it’s your job to eat two frogs, it’s best to eat the biggest one first.” This idea of dealing with the hardest thing first is better known to fans of Brian Tracy (thanks to his legendary anti-procrastination guide “Eat That Frog“).
  2. M.A. Pyc, K.A. Rawson. Testing the Retrieval Effort Hypothesis: Does greater difficulty correctly recalling information lead to higher levels of memory? Journal of Memory and Language, 60 (2009), pp. 437-447
  3. Landauer, T. K., & Bjork, R. A. (1978). Optimum rehearsal patterns and name learning.
  4. Cepeda, Nicholas & Vul, Edward & Rohrer, Doug & Wixted, John & Pashler, Harold. (2008). Spacing Effects in Learning A Temporal Ridgeline of Optimal Retention.
  5. Karpicke, J., & Bauernschmidt, A. (2011). Spaced retrieval: Absolute spacing enhances learning regardless of relative spacing. Journal of Experimental Psychology: Learning, Memory, and Cognition, 37(5), 1250–1257.)

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