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Spaced Repetition

By Juan Carlos


A proven memory technique that helps folks recall knowledge over progressively longer periods.

The concept combines two approaches:

  • Spaced Practice requires learning in short sessions on a longer time horizon.
  • Retrieval Practice involves regularly testing knowledge.

In practice, individuals divide learning time into brief sessions and actively retrieve information on a spaced schedule.

Why Use It

When learning, folks fall victim to Illusions of Competence, a fallacy where one mistakes recognizing information for recalling and using it. You can forget knowledge stored in long-term memory if you do not use it. An example of this phenomenon is languages and losing the ability to speak them over time.

Desirable Difficulty is a concept that illuminates how learning slowly can reliably embed knowledge into long-term memory.

So, instead of studying or re-reading knowledge in large chunks, the learner focuses on testing themselves in short sessions to retain information better. The more they practice, the less often they need to see the information. Testing learned knowledge continues at increasing intervals.

When to Use It

Memories decay over time. This phenomenon is called the Forgetting Curve.

Spaced Repetition is applied in scenarios where learners must retain many items permanently and subvert memory’s natural tendency to decay.

  • Recovery practice is when a learner recalls information immediately after learning it.
  • Flashcards test a learner. These systems deliver new cards and difficult ones more often and old or less complicated ones less frequently.

Applications of the concept include:

  • Recalling facts of any kind.
  • Recalling events from childhood.
  • Learning vocabulary for a second language.
  • Helping patients with memory disorders such as Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, and aphasia.

How to Use It

Memory is encoded information, chemical changes between neurons, stored and retrieved in the brain.

Long-term memory is defined as declarative or non-declarative:

  • Declarative memory is recalled consciously. Examples include lived events and facts.
  • Non-declarative memory is innate knowledge that does not require conscious thought. Examples include swimming, cleaning up, or brushing teeth.

Memories come in two formats, storage strength and retrieval strength:

  • Storage strength is permanent. The brain assesses this information as necessary, and once obtained, it remains available. Recalling and using this type of memory reinforces it.
  • Retrieval strength is not permanent. The brain believes this information is less critical, and it needs to be regularly recalled.

Memory is like a massive library. There is space for all kinds of information, but the catalog plays a paramount role with such a vast array of content. Staying on top of where the information is and how to access it is where to focus your attention.

Spaced repetition spreads out learning over time and can be accomplished with simple tools and processes:

  • The learner recalls a specific piece of information 20-24 hours after initially learning it.
  • A day later, recall the same information again.
  • Increase the time interval each time you recall information.
  • Double the interval each time you answer correctly.
  • Repeat these short sessions anywhere every 36 hours for several days.
  • Most information needs to be refreshed occasionally.
  • As memory fades, retrieving it again keeps it available.
  • When recalling the information fails, then start the process again.

Measure spaced repetition to find out what works best using absolute spacing and relative spacing:

  • Absolute spacing is where you count the number of testing sessions.
  • Relative spacing considers the space between each testing session. An expanding interval is one where the test occurs on days 1, 3, 8, and 12, whereas a uniform interval occurs every five days.

Spaced repetition software is similar to the manual style of learning via flashcards:

  • Question and answer pairs are added to the program.
  • The software’s algorithm displays questions when they need to be recalled.
  • Users note the level of difficulty in retrieving an answer.

Several spaced repetition systems include:

  • The Leitner system is a flashcard-based method where information is sorted into groups based on the learner’s aptitude. If you get an answer correct, the card moves to the next group, but if you are wrong, the card is transferred to the first group. This system focuses learners on the most challenging flashcards.
  • Graduated-interval recall is suitable for audio as it focuses on spacing repetitions every few seconds or minutes at the start. In Pimsleur’s system, the cadence is five seconds, twenty-five seconds, 2 minutes, 10 minutes, 1 hour, 5 hours, one day, five days, twenty-five days, four months, and two years.
  • SuperMemo software is ubiquitous. It stores question and answer pairs in a database. When users answer questions, they grade their difficulty. The spacing algorithm considers these factors to develop a cohesive learning strategy.

How to Misuse It

Spaced repetition apps and algorithms help folks transfer knowledge into long-term memory. The most common modality is a flashcard system, and the goal is to get the correct answer months or years later. However, there are limitations to learning languages in only this way as one may recall words too slowly to be conversational.

Next Step

Spaced repetition is effective because it challenges the brain to retrieve information in expanded intervals when the learner is less likely to retain it. If they answer correctly, the memory is cemented.

The superior memory technique has applications for learning any type of material:

  • Instead of studying for hours, break it down into smaller chunks over a more extended period.
  • Spacing learning over several days and weeks is more effective than one day.
  • Test yourself by retrieving knowledge, not just reviewing and recognizing content.

Start by using the “Leitner System” flashcard method to get going quickly. Then apply the techniques to a version of the process that best works for you.

Where it Came From

Spaced repetition is also known as spaced retrieval, repetition spacing, and expanded retrieval. Hermann Ebbinghaus first noticed a forgetting curve in 1885, and that active recall mitigated information loss. Professor C.A. Mace’s 1932 book “Psychology of Study” introduced the idea that spaced repetition could enhance learning.

In 1939, A series of spaced repetition tests conducted by H.F. Spitzer on 3600 students proved it was effective. Sebastian Leitner developed a flashcard-based method in 1973 called the “Leitner system.” But the concept was not popularized until 1978, when Landauer and Bjork conducted their face-name association experiment.

Nearly a decade later, in 1985, Schacter, Rich, and Stampp found applications for those who suffered from amnesia and other memory disorders. Then in 1989, C.J. Camp extended that to patients diagnosed with Alzheimer’s disease.

Hi, I’m
Juan Carlos

Fueled by a passion for storytelling and excitement for life design, I find joy in reframing narratives to illuminate paths toward fulfillment. My experience spans high-growth startups, filmmaking, and social impact. Through mentoring and coaching, I guide teams and individuals to discover purpose and cultivate a meaningful life.

My Story

I started in film, directing award-winning features such as ‘Know How’ and ‘Second Skin.’ These cinematic endeavors earned me recognition and allowed me to serve as a spokesperson for Adobe. I founded the White Roof Project, a grassroots climate activism campaign that mitigated the urban heat island effect and spurred community-led social change.

I carried my storytelling skills and passion for societal transformation as I transitioned into the startup ecosystem. Initially, I contributed to social impact apps, converting complex issues into accessible solutions. This early experience laid a foundation for my later work, where I led the development of groundbreaking products within high-growth startups. My work has underscored the potential of technology to innovate and amplify the quality of human life.