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Published: October 6, 2026
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Desirable Difficulties in Learning: Why Harder Studying Sticks Better
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Desirable difficulties in learning are study conditions that make practice feel harder and slower but lead to better long-term memory. The main ones are spacing your reviews, interleaving topics, testing yourself instead of rereading, and generating answers before you see them. A difficulty is only desirable if you can overcome it with effort; if you cannot, it simply gets in the way.
Most students judge a study session by how it felt. If the material flowed and the answers came quickly, it seems like a good session. If it was a struggle, it seems like a bad one. The research on desirable difficulties suggests that this instinct is often backwards. Some of the conditions that make studying feel worse are the ones that make it last.
The psychologist Robert Bjork introduced the term in the 1990s, and he and Elizabeth Bjork have written about it extensively since, including a widely read 2011 chapter titled Making things hard on yourself, but in a good way: Creating desirable difficulties to enhance learning. The idea is not that harder is always better. It is that certain specific kinds of effort help memory, while others are just friction.
What are desirable difficulties in learning?
Question: Which study habits actually count as desirable difficulties?
Answer: The well-studied ones share a pattern: each removes a support that makes practice easy, so your memory has to do the work itself. The table shows the five most often discussed.
| Difficulty | What it looks like | Why it feels worse | Easy alternative it replaces |
|---|---|---|---|
| Spacing | Coming back to a topic after days, not minutes | Some of it has faded, so recall is slower | One long session on a single topic |
| Interleaving | Mixing problem types or topics in one session | You must work out which method applies each time | Twenty problems of the same type in a row |
| Retrieval practice | Answering from memory before checking | You see your gaps and get things wrong | Rereading or highlighting |
| Generation | Attempting an answer or explanation before being shown it | You may struggle or produce a wrong first attempt | Reading the worked solution first |
| Variation | Practising with different examples, wordings or settings | Each new version feels less familiar | Repeating the same example until it is automatic |
Each of these has its own guide on this blog. For spacing, see the spaced repetition study method. For mixing topics, see the interleaving study method. For self-testing, see active recall. What desirable difficulties add is the reason they work together: all three trade comfort during practice for memory that holds up later.
Learning and performance are not the same thing
The central idea behind desirable difficulties is a distinction between how well you do during practice (performance) and how much you keep and can use later (learning). The two often move together, but not always. In a 2015 review, Soderstrom and Bjork brought together decades of studies showing that performance during practice can be a poor guide to long-term learning. Conditions that boost practice scores can produce little lasting learning, and conditions that lower practice scores can produce more.
Retrieval practice is a clear example. In a study by Roediger and Karpicke (2006), students who restudied a passage did better on a test five minutes later, while students who practised recalling it did better a week later. If you only checked yourself at the end of the session, rereading would look like the winner.
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See how it worksWhy do students avoid desirable difficulties?
Question: If these methods work, why does almost everyone default to rereading and blocked practice?
Answer: Because our sense of how well we are learning is based on how fluent the material feels, and easy conditions feel fluent. People tend to read that fluency as a sign of learning, even when it is not.
A study by Kornell and Bjork (2008) shows this well. Participants learned to recognise the styles of different painters. Seeing the painters mixed together, rather than one artist at a time, led to better recognition of new paintings. Yet most participants believed the blocked, one-artist-at-a-time presentation had helped them more.
This is the same trap described in the article on why rereading notes is ineffective. Familiarity is pleasant and it looks like progress. A session full of wrong answers feels like a setback, even when it is the more productive one.
What desirable difficulties look like in different subjects
The principles are general, but the practical version depends on what your exam asks you to do. A few examples:
Maths, physics and statistics
Instead of doing all the problems at the end of one chapter, take a mixed set from the last three chapters and work out which method each needs. Before reading a worked example, attempt the problem yourself for a few minutes. Your attempt may be wrong, but it makes the worked solution more meaningful when you read it.
Biology, medicine and chemistry
Draw a pathway or structure from memory before checking the textbook diagram. Come back to it two days later and draw it again. Then explain the same mechanism in a different context, such as a disease or an experiment, which adds variation to plain recall.
Law, history and essay subjects
Write an essay plan from memory before looking at your notes. Practise applying the same argument to a question worded in a way you have not seen. Mix cases or periods within a session so you have to recall which one fits, instead of revising them in neat chronological blocks.
Languages
Produce the word or phrase in the target language rather than only recognising it. Use vocabulary in new sentences instead of the same example each time, and space reviews across the week instead of learning a list in one evening.
When does a difficulty stop being desirable?
The word "desirable" is doing real work. Bjork has stressed that a difficulty is only useful if the learner can respond to it successfully. Difficulty that you cannot overcome does not build memory. It produces guessing, frustration and, often, giving up.
- Testing before any study: trying to recall a topic you have never learned gives you nothing to retrieve. Learn it first, then test.
- Gaps that are too long: if a topic has faded completely, the review becomes relearning from scratch. The gap was too long for that stage.
- Mixing before you can tell things apart: interleaving helps once you know each method. Interleaving from the start, with no grasp of any of them, adds confusion.
- No feedback: struggling with an answer helps only if you find out whether you were right. Always check, and correct mistakes.
- Difficulty from the wrong source: unclear notes, missing explanations or poor sleep make studying harder without making it better.
How to apply desirable difficulties by hand
Getting the level right is the hard part. Too easy and you are back to rereading in disguise. Too hard and you stall. A rough guide is that you should get a fair share of items wrong or slow on the first attempt, be able to work most of them out with effort, and see improvement on the next review.
- Learn a topic properly once. Make sure you understand it before you start making it harder.
- Test yourself before checking. Close the notes and answer from memory, even if the answer is partial.
- Delay the next review. Come back after a day or more, not later the same hour.
- Mix in older material. Once two or three topics are learned, review them together rather than one after another.
- Use your mistakes. Wrong answers are where the learning is. The guide on reviewing practice test mistakes explains how to turn them into review items.
- Adjust when it stops working. If nearly everything is easy, lengthen gaps or mix more. If nearly everything is wrong, shorten gaps and go back to the material.
The last step is the one most people skip, because it means tracking how each topic is going and changing the plan as you go. Doing that across several modules takes more record keeping than most students have time for.
How Sidetracked Day helps with desirable difficulties
Sidetracked Day builds two of these difficulties, retrieval and spacing, into how you study, and adjusts them to your results. It turns lecture slides and course material into active-recall study sessions, so every review asks you to produce an answer rather than reread one.
Review timing adapts to how you perform. A correct answer without a hint pushes the next review further out, keeping the effort level up as an item gets easier. A wrong answer brings the item back sooner and logs it as a weak spot until you answer it correctly without help, so the difficulty does not run ahead of what you can manage. It decides what to study, how and for how long, and you press start. It runs on the web, iPhone and Android.
Build a study system that adapts as you learn
Sidetracked Day helps students move beyond static study plans by adapting sessions, practice, and reviews based on how they actually perform.
Try Sidetracked DayFAQ: Desirable difficulties in learning
What are desirable difficulties in learning?
Study conditions that make practice feel harder or slower but improve long-term retention, such as spacing, interleaving, self-testing, generating answers and varying practice. The term comes from the psychologist Robert Bjork.
Why do desirable difficulties work?
They make your memory reconstruct answers or choose methods on its own. That effort tends to produce memories that last longer and transfer better than those built in easy conditions.
When is a difficulty not desirable?
When you cannot overcome it. Without the background knowledge to attempt an answer, testing only produces guessing. Useful difficulty comes from retrieving and applying what you have studied.
Is rereading a desirable difficulty?
No. Rereading feels easy because the answer is in front of you, which can create a false sense of mastery. Recalling the same material from memory turns that time into a desirable difficulty.
How can I tell if my studying is difficult in the right way?
You get a fair share of answers wrong or slow at first, can work most of them out with effort, and improve on later reviews. Getting everything right means it is too easy; getting almost nothing right means it is too hard.