The Significance of Incremental Reading in SuperMemo: Part II

Image by Nino Carè from Pixabay

This is the part II for “The Significance of Incremental Reading in SuperMemo”. If you haven’t already, please read Part I first.

Quick Terminology Recap

SRS = Spaced Repetition Software

SuperMemo is the one from; NOT the courses, mobile app, application from They are different.

Items in SuperMemo = Cards in Anki; IR = Incremental Reading


I think the reasons behind the benefits of traditional use of SRS (spaced retrieval practice of flashcards) can be translated to and used to explain the benefits of Incremental Reading. Incremental Reading is essentially “spaced repetition-ing” your reading, just like any SRS that would “spaced repetition” your review of flashcards. You may see Incremental Reading as just another application of SRS, this time to reading.

Why do you want to read this way? What are the benefits?

Benefits of Incremental Reading

In terms of practicality:

1. Seamless Integration Between Reading and Remembering

From the learning science’s perspective, Incremental Reading has:

2. Spacing effect (also memory consolidation from sleep)

3. Interleaved effect (both on micro-level and macro-level)

1. Seamless Integration Between Reading and Remembering

First, let me clear up what I mean by “learning”:

1. Learning = understanding and reading new things

2. Remembering = understanding and memorizing what you learned

Learning and remembering are inextricably interwoven, but explicitly separating them helps me get my points across about Incremental Reading.

During learning, you first try to understand a new idea or concept. Then, if you think that piece of information is worthy enough to be remembered, you move on to the second step: remembering: you memorize it by making flashcard(s) out of it.

In Anki, you are only doing the remembering part. You are not reading anything new in Anki. Without SuperMemo (Incremental Reading specifically), you would need to learn traditionally (reading with a hard copy, lecture notes, PDFs), then import important parts into Anki.

On the other hand, SuperMemo blends these two components seamlessly. With IR, learning and remembering are blended into one: you read (learn) and review (remember) simultaneously.

I don’t have to decide what and when to read

In SuperMemo:

Topics keep the knowledge you want to learn (i.e. things you want to read about)

Items keep the knowledge that you want to remember (i.e. the knowledge you already possess, but might forget)

In SuperMemo, I would encounter reading materials I imported (online articles, chapters of books, research papers etc). While reading, I will extract portions of texts and then (immediately) create clozes or Q&As.

By loading all the learning materials into SuperMemo, I just need to prioritize, and SuperMemo would show them to me accordingly. With such integration, I don’t have to decide what and when to read. This is the same as having a SRS to schedule all the card reviews for you.

I can rest assure that I will not miss anything. If it’s important enough, it will show up earlier. I may set an article to a low priority because I have yet to acquire enough background knowledge. After a month of reading supplementary articles, I can proceed and read the original article. Without IR, I would need to manually set up a calendar reminder to remind myself going back to read it again a month later, and that’s fine for one article. Imagine having more than a dozen of such articles and having to do it every time?

You may say,

I can manually decide when to read a particular article. I don’t need a software to decide it for me.

Yes, it’s true… if you have a small reading collection. When you have a lot of reading materials, the ever-increasing difficulty of managing your reading materials can be paralyzing. When should you read this article? Have you read that article? Where was I the last I read this article?

For the sake of argument, let’s say you managed to manually prioritize and schedule your reading. However, it’s still not ideal. How do you decide when to read an article? Just because you “feel like it”? Due to the priority bias, you will always feel that new reading materials are more important and interesting, and thus, compelled to read them first. But you forget that your old reading materials were once “new” too.

Just because “manually prioritizing and scheduling your reading” is manageable doesn’t mean it’s optimal. For the same token, it’s theoretically possible to have 10,000 PAPER flashcards and to calculate individual review schedule every time you review a card. You can still argue it’s “manageable” but no one would say it’s optimal, effective and efficient.

Reading incrementally outside of SuperMemo is like doing paper flashcards (The Leitner Box System): you can but you just wouldn’t.

Besides, the integration between reading and remembering entails more than just knowledge management and prioritization. Incremental Reading is a form of interleaved practice with the spacing effect.

2. Spacing effect: Spaced Re-reading Introduces Forgetting

According to Robert Bjork’s the New Theory of Disuse, disuse is a key factor in forgetting. From Making Things Hard on Yourself, But in a Good Way: Creating Desirable Difficulties to Enhance Learning:

Forgetting (losing retrieval strength) creates the opportunity for increasing the storage strength of the information or skills.

Only after you’ve forgotten (at least to a certain extent) can you trigger retrieval and encoding activities that strengthen the memory because gains in storage strength are a decreasing function of current retrieval strength. In other words, “forget a little, then refresh your memory” helps a lot with memorization.

IR is an application of spaced repetition. Therefore, the benefits of spaced repetition could be translated to IR and used to explain the benefits of IR. When you read an article on Mar 3, then pick up where you left off on May 4 (a month later), some forgetting is bound to occur. You have to reload your memory, such as, what the article is about by retrieving relevant context, what the main points are. You have to revisit (retrieve) those clusters of neurons. Spacing allows time for forgetting to set in so that you can get the maximum benefits of memory (re)consolidation.

Macro-interleaved practice (more on this later) also means that there are more spacing between content from the same subject. The lag effect tells us that there is an advantage of spacing with longer lags over shorter lags.

Spaced Re-reading is Better Than Massed Re-reading

From Improving Students’ Learning With Effective Learning Techniques:

One aspect of the learning conditions that does significantly moderate the effects of rereading concerns the lag between initial reading and rereading. […] spaced rereading usually outperforms massed rereading.

In other words, what makes re-reading effective? The time passed between 1st and 2nd reading sessions.

In a recent study by Verkoeijen, Rikers, and Ozsoy (2008), learners read a lengthy expository text and then reread it immediately afterward, 4 days later, or 3.5 weeks later. Two days after rereading, all participants completed a final test. Performance was greater for the group who reread after a 4-day lag than for the massed re-readers.

I’m aware that spaced re-reading is not the same as Incremental Reading:

Re-reading: Read the whole article from start to finish again

Incremental Reading: pick up where you left off last time

This is a leap of faith so take it with a grain of salt: I believe that the benefits of re-reading could be translated to Incremental Reading. They’re similar in nature: both include spacing between reading sessions. I believe IR is even better: there are a lot of active processing and reviewing during and between reading sessions, whereas in re-reading you are merely engaging in passive re-reading.

Just like it’s far, far from enough to review a flashcard once, reading an article once is not enough. But no one wants to read the same article 5 times, even if it’s spaced, say across 5 months. So what if you read that article once, spaced across 5 months? This is Incremental Reading: enjoying the benefits of spacing without re-reading. The extracts and subsequent clozes and Q&As are the foundations that support and provide context when you continue reading from your last read-point.

“Sleep on it”: Memory Consolidation from Sleep

The prophetic Roman rhetorician Quintilian stated:

It is a curious fact, of which the reason is not obvious, that the interval of a single night will greatly increase the strength of the memory… Whatever the cause, things which could not be recalled on the spot are easily coordinated the next day, and time itself, which is generally accounted one of the causes of forgetfulness, actually serves to strengthen the memory.

Processing the same article across days, weeks, or even months realizes one of the strongest ways for memory consolidation: sleep. I may write about how sleep is crucial to memory formation and consolidation. But for now, just realize that with IR, just like any spaced repetition, sleep is automatically incorporated. Nurturing creative and insightful ideas, achieving transfer of knowledge take time. One of the magic ingredients is sleep.

3. Interleaved Practice (Both on Micro-level and Macro-level)

Interleaved practice is alternating between different kinds of items. The opposite is massed practice, in which you study content from the same topic or type before moving on to the next topic or type.

Basically, Interleaved practice is just mixing things up. With IR, you are interleaving between reading (topics) and remembering (items such as Q&A and clozes). IR is interleaving at two levels: micro and macro. Such interleaved practice of learning and remembering is magnificent:

1. Micro-level: interleaving between reading an article and remembering the items produced (such as Q&A and clozes) from that article.

2. Macro-level: interleaving between reading different articles and remembering their corresponding items.

Micro-level (Same Reading Material):

1. Interleaving between different items of article A: Cloze A4 → Q&A A2 → Cloze A5

2. Interleaving between reading article A and remembering items from article A: Read Extract A1 → Q&A A2 → Cloze A5 → Continue reading Article A → Extract A5

Macro-level (Different Reading Materials):

3. Interleaving between 1. and 2. with different reading and reviewing materials. When you many different reading materials, you are interleaving at a macro-level.

Incremental Reading in SuperMemo is interleaving of all reading and reviewing materials. Not just interleaving items but including all reading materials. You review as you learn; learn as you review.

For example, SuperMemo will show me the following in such sequence:

An extract of article A –> An item about history –> An item about nutrition –> Whole article A (last reading set-point) –> An item about molecular biology –> Whole article B (last reading set-point) –> another extract of article A

It’s like throwing everything into a blender:

Micro-level: Throwing fruits, such as apples, oranges, watermelons into the blender. A fruity smoothie

Macro-level: Throwing fruits, vegetables, potatoes, meat, eggs, honey into the blender. A probably weird-tasting meal replacement

Simply put, Incremental Reading = Spaced repetition of “reading interleaved with reviewing”

In SuperMemo’s Incremental Reading, the learning process will intermingle reading of new articles with reviewing your items.

The algorithms determine the timing of (1) repetitions of Q&A material and (2) reviewing reading material.

The algorithm determines when to show you a particular reading material, its extracts and its items. Generally speaking, SuperMemo puts a higher priority on clozes and Q&A, so they will always show up before its corresponding article. You’ll always review them before further reading the article.

Why Would You Want to Jumble Everything Together?

From “Improving Students’ Learning With Effective Learning Techniques”, interleaved practice is a better learning strategy than massed practice. Is this macro-interleaving better than micro-interleaving? Again, there is a leap of faith. I believe macro-interleaving is equally, if not more, beneficial than micro-interleaving. As far as I know, the research only illuminates on the benefits of micro-interleaving, such as solving different solids (cubes, spheres, prisms), rather than massed practice (all spheres –> all cubes –> all prisms) in one study session.

Holistic Learning vs. Sequential Learning

I always believe that a holistic approach is better than a sequential approach: Forwarding multiple subjects slowly and simultaneously is better than forwarding one subject quickly and sequentially.

Each day:

Physiology: 1 step forward

Programming: 1 step forward

History: 1 step forward

is better than

Physiology: 3 steps forward

Next day:

Programming: 3 steps forward

Next day:

History: 3 steps forward

How does this Holistic vs. Sequential Learning Relate to Incremental Reading?

Sequential learning is massed practice at a large scale. Holistic learning is interleaved practice at a large scale. Incremental Reading is holistic learning.

Imagine you have 3 cups with the same capacity. You can only fill up each cup with a specific liquid. Each cup is emptied every day. Your goal is to fill them up as much as possible.

1st: Water

2nd: Tea

3rd: Coffee


With a limited capacity, there’s only so much you can fill up a particular cup before spilling. How do you maximize the amount of liquid filled? Fill up all three cups instead of one.

If you keep filling water to the water cup, after exceeding its capacity, all the extra water will go to waste. You leave other cups empty, wasting the opportunity to fill them up. This is the same as studying the same subject for a day (massed practice). There’s only so many concepts and information you can cram before “overfilling” the learning capacity for a particular subject.

In other words, I think there is a limit in how much you can transfer from short-term memory to long-term memory for a particular subject. Your learning capability for a particular subject has to be in conjunction with the growth of its prior knowledge. Increasing your expertise and building prior knowledge for a particular subject takes time. Building up expertise requires integration of ideas and transfer of knowledge, which takes a lot of time. You just can’t rush.

This is probably a lame analogy, but I hope you get the idea.

Closing Remarks

With Part I and this Part II, they are all I have to say about Incremental Reading. I hope this article has convinced you to give IR a try. ALso, this is currently the best video on getting started with Incremental Reading: Starting with SM Going through the IR Manual.