Interleaving practice—mixing related concepts instead of drilling one at a time—produces better learning efficiency and retention than traditional study methods. Peter Hollins explains the neuroscience: why this approach strengthens working memory, improves skill acquisition, and builds mental flexibility for long-term retention.

⏱ CHAPTERS
0:00 Intro
2:15 Interleaving Technique Overview
4:28 Benefits and Challenges of Interleaved Practice
7:10 Spacing Learning for Better Memory Retention
10:25 Zone of Proximal Development (ZPD)
13:15 Minimizing Extraneous Cognitive Load
16:05 Managing Cognitive Overload in Study Sessions
19:18 Strategies to Reduce Mental Fatigue and Enhance Focus
22:42 Illusion of Productivity Through Cramming
27:15 Pretesting as a Learning Strategy

If you’re looking to boost your learning efficiency and mental performance, don’t miss out on Peter Hollins’ insights into powerful study techniques like spaced repetition, active recall, and interleaving practice. These methods can significantly enhance long-term retention and skill acquisition by reducing cognitive load and optimizing memory consolidation—perfect for anyone eager to elevate their working memory and overall cognitive abilities through neuroscience-backed strategies.

Are you tired of feeling stuck in a rut with your studies?
Doing the same drill on the same topic for a solid hour?
And somehow it’s still feeling like nothing’s sinking in?
Well, there’s a reason for that.
And it’s not that you’re not working hard enough.
It’s that you’re working the wrong way.
Today we’re covering three techniques from Peter Holland’s book, Sticky Learning, that aren’t about what you study, they’re about how you structure the session around it.
First up, Interleaving.
Interleaving means mixing related concepts together instead of drilling one at a time.
It sounds almost too simple to matter, but the difference in what actually sticks is not small.
As we use our memories, the things we recall become more recallable.
Things in competition with the memories become less recallable.
Every skill we want to learn is really made up of smaller skills.
It makes sense then to break things down, master each chunk separately, then combine everything.
However, many of us unwittingly stop just short of the combine everything step and get stuck for far too long in the one skill at a time zone.
In real life, however, we usually use all of our skills at once.
If we want our mastery to be flexible, adaptive, and contextual, then our practice has to reflect this.
Enter Interleaving.
Interleaving is the evidence-backed technique of structuring your practice or study around mixed combinations of related concepts rather than single concepts at a time.
What’s the benefit?
With practice that is interleaved, you store information more deeply, retrieve it more reliably, and allow your brain to build essential patterns and connections between concepts.
blocked practice or masked practice.
One-at-a-time learning in sequential chunks is also useful, but it doesn’t challenge your brain to actively pull together everything it’s learned and find new strategies to solve unfamiliar challenges and problems.
A good balance is beginning with blocked practice then increasingly use interleaving to acquire mastery.
Along with spaced repetition, interleaving is one of the most extensively studied and evidenced techniques for creating deep comprehension and lasting retention.
Used together, they are a powerhouse.
For many students, the idea of interleaving seems trivial at first.
But try it for a period and the effects will be very evident.
You improve your mental flexibility.
You enhance your ability to transfer skills to other areas.
You become a more creative problem solver.
You gain confidence.
You create more secure long-term memories.
By constantly asking your brain to retrieve, compare, reinforce and apply knowledge in various settings and across various activities over time,
Your learning becomes rich and three-dimensional.
Mix tasks into your daily study or work routine.
In school, were you indoctrinated into the one hour per topic dogma?
It goes like this.
One study session equals one subject.
So first is math, then chemistry, then English lit.
And in each of those hours, you focus on just one topic at a time.
One day in math class, you learn long division.
The next, you learn multiplication.
With the interleaving approach, you mix things up.
For example, math class might include working on problems from all different chapters in the textbook.
multiplication, division, fractions, and more.
Or you may only work on fractions, but switch up the kinds of problems you tackle and change the format of the practice questions.
Instead of AAAAA, BBBBB, CCCCC, DDDDD, you have AAACD, BDACA, DDCBB, BABCAC,
If you’re busy in the middle of an A block, your brain gets lazy.
It knows that its next task is A, so it relies on short instead of long-term memory.
It gets complacent.
You learn less.
On the other hand, every time you switch, you ask your brain to actively recall previous information.
You’re challenged to find connections between activities.
You’re forced to carefully consider your problem-solving approaches, not merely using a technique because that’s what you’re doing that day.
This enhances your memory, keeps you on your toes.
Interleaving your daily practices fairly straightforward.
One, break your session into smaller chunks.
Two, rotate between these chunks so you’re never doing the same thing twice in a row.
So if you’re learning from a chemistry textbook, spend your study hour mixing up exercises and tasks from four different chapters, or tackle the same chapter but in multiple ways.
One essay question and a few short form answers, some multiple choice quizzes.
You can also add variety in the format of your materials.
For example, instead of slogging away reading one chapter in the textbook, you could spend 20 minutes watching a video about Chapter 3, taking notes, spend 20 minutes making a mind map or flashcards for Chapter 4, spend 20 minutes doing a practice test paper for Chapter 5, asking a friend to grade you.
You’re working on the same topic.
There are countless ways to slice and dice your material.
All that matters is that you’re keeping limber and cognitively flexible as you switch between tasks.
Once you get the hang of interleave practice, you may notice that it’s a little more challenging and engaging.
Time seems to go a lot quicker.
You learn more.
With interleaving practice, you often work harder, but you prevent the learning fatigue that comes from dull repetition.
Research into the effects of interleaving has been encouraging, with most finding that recall and retention has drastically improved when material is interleaved rather than blocked.
Furthermore, a research review of a whopping 254 studies found that, on average,
People were able to recall about 10% more information when using spaced repetition compared to masked practice.
Can you imagine how effective the two might be when combined?
Spread learning sessions across your week.
Cramming is a terrible habit.
Your exhaustion and panic may give the illusion that something is changing in you.
In truth, a brain that is depleted and overstressed is a brain that cannot process, consolidate, or retain information effectively.
Combine spaced repetition with interleaving by evenly spacing out your work over the course of a week.
Break that exhausting study marathon down into 20 or 30 minute chunks, then evenly distribute those chunks across your calendar, remembering to mix things up so you’re not spending too long on any one topic, approach, or activity.
cramming gives the illusion of productivity, but spacing your learning helps your brain consolidate that knowledge into long-term memory.
Instead of doing one marathon session, break your learning into 15-30 minute chunks spread across the week.
spaced, interleaved practice is not just more effective, it also allows you to squeeze in personal development projects around your existing commitments, making gains, even though your schedule only has small pockets of time here and there.
Instead of wearing yourself out with two straight hours of French practice on a Sunday afternoon, for example, try this.
Monday, 15 minutes of new vocabulary, e.g.
travel words.
Tuesday, 15 minutes drilling vocabulary flashcards.
Wednesday, 25 minutes practicing a conversation exercise online with the fellow student.
Thursday, 15 minutes reviewing and revising
plus a vocabulary quiz.
The spaced repetition means you’re far less likely to slide down that forgetting curve.
And did you notice you can often get away with investing far less study time overall, because you are utilizing the time you have so much more efficiently.
Build in quick reviews of past material.
One of the reasons interleaving works so well is that it encourages the brain to engage in active recall.
Each attempted recall has to be new.
You cannot fall back on short-term memory or momentum.
No shortcuts, no assumptions.
For example, you can’t look at a math problem and think, oh, I have to solve this in XYZ way because today is XYZ day and I’m doing an XYZ exercise.
So I’ll just do what I did for the last question.
Instead, you have to ask, what kind of problem is this?
What is the question asking me?
Have I seen this kind of thing before?
What tools do I have?
You can encourage this kind of deliberate, flexible thinking by spending the first few minutes of every session reviewing prior material.
quickly summarize in a sense or two what you covered in the last session.
Quickly scan over your notes to refresh your memory, whether they’re summaries, mind maps, flashcards, or diagrams.
Do a quick five question quiz.
Without consulting your notes at all, try to see how much of the last session you can recall from memory alone.
Notice the gaps.
If you’re learning a particular athletic, musical or creative skill, quickly drill it, start to finish.
Cognitive load management, lighten the mental load to unlock deep learning.
It’s not the load that breaks you down.
It’s the way you carry it.
Lena Horne.
We know that we need to stay in the flow zone.
We also know that for deep learning to occur, we need to be inside our ZPD, the zone of proximal development.
Chick-Sent-Mahalia’s flow model is about the optimal range for focused attention and absorption
The Gotsky’s model is about the optimal range for development and learning.
In this chapter, we’ll look at a similar principle, but through psychologist John Sweller’s model, which is about the optimal range for cognitive effort.
In essence, there are not really different theories, but the same underlying concept seen through different lenses.
The underlying concept?
Optimal performance is about being in the optimal range.
Sweller’s cognitive load theory begins with the fact that the brain’s cognitive powers are limited.
Something that’s easy to forget in our endless hustle and productivity culture.
Working memory is like the surface of a table.
We can lay out a few things on the table and get to work.
but the tabletop is fixed in its dimensions.
Put too many things on the table.
Stuff falls off.
Stress and chaos.
Productivity drops.
Our working memory is the same.
It too has fixed dimensions and suffers when overloaded.
Forgetting things?
Feeling stressed and overwhelmed?
You might be disrespecting your brain’s natural limitations
Some cognitive psychologists set the limit at a mere handful of ideas, just seven or so, that can be held in the working memory at any one time.
See the famous The Magical Number Seven, plus or minus two, some limits on our capacity for processing information by George A. Miller, 1956.
It’s the same idea again.
Our brain is built to handle a certain cognitive load, but that capacity is not infinite.
Beyond a certain point, cognition suffers.
Not all cognitive load is the same.
Intrinsic load.
A task’s inherent difficulty, i.e.
how challenging, large, or complex it is.
Brushing your teeth?
Low intrinsic cognitive load.
Writing an entire screenplay in three days?
High intrinsic load.
Extraneous load.
Cognitive demands are rising not from the task itself, but from the environment, i.e., additional impediments and distractions, for example, a fly buzzing around your head while you’re trying to focus, a teacher with a hard-to-understand accent, a cluttered disc, outdated learning materials in a format you dislike, physical discomfort,
Germain Load The mental effort you make to form helpful new connections, schemas, or mental frameworks.
Germain Load is effortful, but improves learning in the long run.
Actively connecting what you already know to the new things you’re learning, creating helpful mind maps, visual aids, mnemonics, diagrams, etc., using analogies, stories, or metaphors to bridge your understanding to an unfamiliar topic.
The cognitive load is multi-dimensional, meaning the demand comes from many different directions.
For example, even an easy task will feel difficult if we’re in a highly distracting environment, like trying to read a book during a metal concert.
An extremely difficult task can be achieved if we have enough time and the right learning tools to digest it.
parsing-sweller’s theory down.
We discover four main goals with respect to optimizing our cognition.
Goal 1.
Stay comfortably within our optimal cognitive range, i.e., neither under nor overloading our capacity.
Goal 2.
Manage intrinsic load.
Find ways to work around the tasks in-built challenge.
Goal three, minimize extraneous load.
Cut down, as much as possible, on noise, distractions, and irrelevancies.
Goal four, maximize germane load.
Do what we can to use tools to help us process, absorb, and retain what we’re learning.
Deliberate, masterful learners understand the art of self-regulation.
They are self-aware and know when they’re outside their optimal range.
Anyone can notice that they’re not performing very well on a learning task, but it takes a little something extra to know why you feel that way and what to do to correct the situation.
First things first, being cognitively overwhelmed is not a sign of stupidity or laziness.
Feeling depleted doesn’t mean you lack passion or discipline.
Running out of steam doesn’t mean that something’s going wrong or that you need to drastically change up your process.
There’s no need to beat yourself up if you discover your cognitive performance dipping.
Read it as a neutral sign and simply adjust.
Here are some signs that you’re simply asking too much of your brain.
You’re struggling to comprehend certain things, feeling confused.
Emotionally, you’re stressed and frustrated.
You’re falling back on old habits and finding it hard to be creative.
You’re not holding on to things.
You’re more forgetful.
Your performance is dropping.
You’re losing accuracy, speed, power, etc.
How can I reduce cognitive load right now?
We lower some useful practical ideas.
Chunk and sequence information to reduce overwhelm.
Goal.
Manage intrinsic load.
Imagine that your long-term memory is a giant open field with plenty of space to store learned information.
The catch is that the only way to access this giant field is through a teeny tiny hole in a fence.
There’s enough space in the field for a big difficult concept.
But how are you going to get it through that teeny tiny hole in the fence?
Answer.
Cut it up.
Difficult tasks are always going to be difficult.
We can’t change that fact.
What we can do is break those tasks down into smaller chunks that we can process one step at a time.
This reduces intrinsic cognitive load.
Chunking is the name given to this breaking down process.
Always be simplifying.
If you encounter a challenging formula, sentence, or concept, break it down, number by number, word by word.
Just try to understand one piece at a time, then move on to the next, as though you are taking small bites.
Use pictures, diagrams, and mind maps.
A picture paints a thousand words.
Condense information in one place, and experiment with representing concepts in a visual rather than verbal way.
Use analogy and metaphor.
What is the new concept like?
How does it connect to something you’re already familiar with?
Make it real.
Experiential learning is more memorable.
Find ways to get hands on and try things out for yourself if possible.
You may gain new insight and understand by being out there in the field.
Tell stories.
Human beings find it easier to understand and care about narratives they’re emotionally invested in, so craft stories that bring abstract ideas to life.
Connect concepts directly to yourself and find the deeper meaning in context.
As an example, if you’re studying for a history exam, don’t get intimidated by the whole syllabus.
Just take it steady with one section at a time.
If the chunk still feels overwhelming, then just break it down further.
Don’t be alarmed if some material is tricky.
If you feel stuck, eliminate the lowest hanging fruit first.
Change up the material format.
Take a mini-breaker.
Play around with interleaving.
If the task feels more psychologically manageable, it’s also likely to be more cognitively manageable.
Eliminate distractions and simplify your learning environment.
Goal.
Minimize extraneous load.
It is not just your internal environment that matters in learning, but your external environment too.
Your physical environment reflects and influences your mental state, including your ability to carry a mental load, clutter, distractions, interruptions, temptations, discomforts, noise.
If you’re experiencing a lot of mental distraction,
It may be because you’re in an environment with high extraneous load.
Your desk is messy.
There’s noise outside and your phone pings every five minutes.
You’re cold and you’re annoyed that one broken letter on your keyboard, any of four other browser tabs open, and there’s something delicious in the kitchen you keep thinking about.
Outer clutter and noise are usually continuous with inner clutter and noise.
Reduce one, you’ll reduce the other.
All of this eats up mental bandwidth while giving you nothing in return.
The only solution is to reduce it as much as possible.
Clear your desk of everything except the materials you’re currently working on.
Silence notifications and remove phones and devices completely.
Use apps and tools to block access to time-wasting sites, streamline your desktop, and cut down on digital distraction.
Alert everyone that you’re busy and not to be disturbed.
Set boundaries and protect them.
Make sure your workspace is calm, well-lit, and at the right temperature.
Think comfort, not luxury.
Have all your tools and materials organized within reach and in good working order.
Rewrite instructions to be simple and clear and try to trim away extraneous information by paraphrasing or summarizing.
Use tools and apps to streamline your work process and give you less to worry about.
Naturally, be mindful that these tools and apps are themselves not becoming a source of distraction.
Be mindful of your attitude.
Create a positive mental environment by staying open, curious and optimistic rather than approaching learning tasks with dread and resentment.
Mentally prepare yourself with a little ritual to mark the beginning of a study session.
light a candle, do a few minutes of visualization or meditation, or scribble random worries in a journal to tackle later.
Link new knowledge to what you already know.
Goal.
Maximize germane load.
As they say, don’t work harder, work smarter.
Any learning activity is going to take time, effort and energy.
So think carefully about where you’d like to invest these limited resources.
Instead of working hard to build something from scratch, piggyback off of something that’s already been built.
Learning is not just additive, i.e., you keep dumping new facts and information onto the pile of existing facts in your brain.
Instead, the sum total of your knowledge is arranged like a web.
Everything connects meaningfully to everything else.
To make new learning last, you need to actively wire it into this web.
Cramming feels productive.
It’s almost never productive.
What actually works is the boring version.
20, 30 minutes at a time, spread across your week, mixed up, rather than sorted into neat blocks.
Less total time and better retention.
Pretesting and quizzing yourself a shortcut to deep learning.
The greatest enemy of knowledge is not ignorance.
It is the illusion of knowledge.
One way to ask yourself important and revealing questions is to quiz yourself.
Though self-quizzing may seem fairly simple and obvious, the testing effect, as it’s called in cognitive science, is a powerful way of turning passive study into an active deep learning process.
Have you ever studied for ages for an exam, only to sit down on the day and find that your mind has gone completely blank?
It’s incredibly frustrating.
At the time you studied, you truly felt like you understood all of the material and felt confident in what you knew.
So what happened?
The answer is that you failed to train recall.
In fact, certain study approaches can mean that exam day is actually the first time you’re asking your brain to recall that information.
The blankness you feel?
That’s actually your true level of understanding.
And your prior perception of confidence was an illusion.
Reviewing, reading, rereading, highlighting, going over notes.
We’ve already seen that these kinds of activities keep you busy and make you feel like you’re doing something.
But what are you really doing?
The thing that truly counts is recall.
Because in an exam situation, at least recall is the only way to outwardly demonstrate your retention.
If you cannot retrieve everything you’ve mentally embedded, then you haven’t learned.
It’s not enough to be familiar with content.
It’s not enough to recognize it.
It’s not enough to run your eyes over the words and, for that brief moment, understand it.
The thing that truly shows whether you’ve truly grasped the concept is if you can recall it from memory and reproduce it.
This is why testing is so important, because it constantly reveals your actual level of mastery.
This means you have a precious opportunity to zoom in on weak spots and fix them now.
Set of waiting till exam day to discover that your grasp is weaker than you thought.
reading and rereading?
That only trains your reading muscles.
Practicing recall?
That trains your recall muscles.
Pretesting means sitting down and breezing through your exam paper, because by that point, it’s something that you’ve already done dozens of times before.
passing or failing a practice test?
That’s not what’s important.
The value of self-testing lies in what it shows us about our own learning process.
After all, much of what we learn never undergoes the corrective process of formal testing.
That means that the things in life we are never tested on, those are the things where the illusion of knowledge poses the greatest risk.
Don’t assume test.
Every time you retrieve a fact, solve a problem, or explain a concept without consulting your notes, you’re cultivating a more durable, more connected sense of understanding.
Start with pretesting, even before you know the material.
Reading and rereading notes may feel comforting, and it’s certainly a task you can do with half a brain at times.
Unfortunately, spending hours this way brings you little gain.
Even if you’re going to the effort of diligently marking your notes up with colored highlighters, self-test and do it often.
Plan mini quizzes all along your study journey.
before you even start to prime your brain and get it alert and on the lookout for relevant material when it encounters it.
During the process of learning to guide and shape your engagement, after you’ve learned some new information to check your retention,
you do not need to wait until you understand everything to test yourself.
Testing yourself is how you begin to understand everything.
Using a few short questions, snippets from an actual exam paper or practice questions, even if they’re of your own making,
tip.
You can also jot down a few questions you have about the upcoming information.
This way, as you work through it, your brain will be actively looking for answers, meaning you engage more deeply.
Your brain always wants to reduce uncertainty, so if you pose a question but don’t answer it, you boost engagement as your brain actively seeks to close that open loop.
pretesting boosts your curiosity and engagement, shows you what you already know and understand, and encourages you to actively consider what you are expected to learn from the upcoming material.
Before reading a chapter or watching a lecture, write down three to five questions you think might be answered.
Even if you get them wrong, you’re training your brain to anticipate and retain what’s coming.
Later, answer the same questions again to measure your progress.
Another great side effect of pretesting is that it gives you something to compare your progress against.
use self-quizzing to pinpoint gaps and direct focus.
It is so tempting as a student to simply focus on what you already know.
It feels familiar and safe, and you get the irresistible confirmation that comes with the thought, yep, I really get this.
I understand this.
I know my work.
Two things.
One, what benefit is there in revising what you already know?
Two, are you sure you really know it or are you just really used to reading it?
Self-testing is a lot less fun because you don’t get that instant satisfying hit of recognition, but you get something better.
Self-testing forces you to look at what you don’t know and devise a roadmap for getting better.
Self-testing doesn’t have to be prolonged or complicated to be effective.
Read a paragraph or a page, close the book, and then recite out loud from memory everything you’ve learned.
Then open the book and see what you missed.
Highlight that.
Later, try again this time focusing on those highlighted pieces.
Break a practice test paper down into chunks and complete a few questions after the relevant section in your material.
Divide your own questions.
For example, you can convert section headings or titles into questions, collect a few, and periodically pause to quiz yourself.
Example, the beginning of the Roman Empire becomes, what year did the Roman Empire officially begin?
Challenge yourself to reproduce charts, diagrams, and float charts as you encounter them.
Simulate real test conditions to build confidence and recall.
Test conditions for you may not entail sitting down to a literal written test.
Test conditions might be a musical recital or other performance, a meeting or presentation, an important interview, a sports game or athletic performance,
a complicated surgery or procedure, a challenging event.
Of course, some of us do go blank during exams or forget everything we’ve learned not because we haven’t done enough self-testing, but because our self-testing hasn’t been a true instance of active recall.
The speech you practice delivering in the comfort of your own home to your cat on the sofa suddenly seems to stick in your throat when you’re in a giant room packed with dozens of people, bright lights blinding you.
Real-life conditions contained heightened stress and anxiety, increased levels of extraneous cognitive load, increased unpredictability.
There’s not as much in our control.
To gain more lasting confidence in our practice sessions, our self-testing needs to reflect real test conditions as closely as possible.
Do a few dry runs of your performance in the venue you’ll actually be using.
Tackle the task at the same time of day, wearing the