Desirable Difficulties Explained: Why Harder Study Helps
“Desirable difficulties” is a term from memory research, associated with the psychologists Robert and Elizabeth Bjork. It describes a frustrating pattern: some ways of studying feel harder and produce worse performance during practice, yet lead to better memory and transfer later. The learner goal here is to understand the idea well enough to recognise which kinds of struggle are worth keeping, which are just friction, and how to redesign a study week around the useful kind.
The core idea: performance is not learning
Researchers distinguish between performance (how well someone does right now, during or just after practice) and learning (what lasts and can be used days or weeks later). The two often move together, but not always. Rereading a chapter three times in a row makes the material feel familiar and boosts immediate performance. A week later, much of it may have faded.
Some study methods reverse that pattern. They make practice slower and more error-prone, but the effort of reconstructing information, choosing a method or adapting to variation appears to strengthen what remains later. That is why these difficulties are called desirable: they cost something now in exchange for durability.
The catch is that people judge their learning by how practice feels. Smooth, fluent study feels like progress. Effortful study feels like failure. Without knowing about this gap, a learner can easily abandon the methods that help most.
The four main desirable difficulties
| Difficulty | What it looks like | Why it feels hard | Easier alternative it replaces |
|---|---|---|---|
| Retrieval practice | Answering questions or recalling from memory before checking | Gaps and errors become visible | Rereading notes or highlights |
| Spacing | Spreading study of a topic across days or weeks | Some forgetting occurs between sessions | Cramming one topic in a single block |
| Interleaving | Mixing different problem types or topics in one session | Each item requires choosing the right approach | Practising one type repeatedly (blocked practice) |
| Variation | Practising a skill in changing conditions or formats | Less routine, more adjustment | Repeating under identical conditions |
Each has its own detailed guide on this site. For spacing schedules, see a spaced practice schedule. For mixing problem types, see interleaving practice. For starting to test yourself early, see self-testing before you feel ready. This page connects them under the single principle they share.
Other techniques are sometimes grouped under the same heading, such as generating an answer before being shown it, or reducing how much feedback is given during practice. The common thread is the same: the learner has to do more of the mental work.
When difficulty is not desirable
Not every struggle helps. A difficulty is only desirable if the learner has enough background to eventually succeed. Recall practice on material never studied produces guesses, not learning. Interleaving five problem types before any one is understood produces confusion. A badly written textbook, a noisy room or a confusing app interface are difficulties too, but they make learning harder without making it stronger.
A practical test has three questions:
- Is the effort directed at the thing being learned (recalling, choosing, applying), or at something unrelated (decoding poor instructions, fighting distractions)?
- Can the learner get it right some of the time, perhaps half or more, with effort?
- Is there feedback soon after, so errors get corrected rather than repeated?
If the answer to all three is yes, the difficulty is likely useful. If the learner is getting almost nothing right, step back: restudy, use worked examples, or reduce the mixing until the basics are in place.
A worked example: Lucas and the plumbing course
Lucas is 47 and training for a career change into plumbing. His evening theory course covers regulations, pipe sizing and heating systems. His habit is to reread his notes on each topic until they feel familiar, then move on. His first mock test score disappoints him: material he “knew” on Sunday was hazy by Thursday.
He redesigns his week using the four difficulties. He turns notes into questions and answers them before rereading (retrieval). He revisits each topic two days later and again the following week (spacing). For pipe sizing calculations, he mixes problems from different scenarios instead of doing ten of the same kind (interleaving). For regulations, he practises explaining rules both in writing and aloud to his partner (variation).
His sessions now feel slower and more frustrating. He tracks a simple measure: on Fridays, a ten-question quiz on topics from the previous week, done without notes. Over the next month his Friday scores trend upward, while his sense of how well each session went stays mixed. The quiz, not the feeling, becomes his guide.
Guided exercise: convert one study week
- List what is being studied this week and how: reading, rereading, watching, practising problems.
- For each activity, mark it F (feels fluent) or E (feels effortful).
- Swap at least two F activities for desirable difficulties. For example, replace a reread with a closed-book recall of the main points, or replace a block of identical problems with a mixed set.
- Split any single long session on one topic into two or three shorter ones on different days.
- Schedule a short delayed quiz at the end of the week covering material from the start of the week.
- Afterwards, note the quiz score and how the week felt. Compare with a previous week if possible.
Printable weekly checklist
- At least three recall sessions before rereading
- Each main topic visited on at least two separate days
- At least one mixed practice set
- One skill practised in a different format or setting
- Feedback checked after every recall or practice set
- Delayed quiz at the end of the week
- Score recorded alongside a one-line note on how the week felt
Common mistakes
- Mistaking frustration for failure. Hard sessions can be productive. Judge by the delayed quiz.
- Adding difficulty too early. Mixed practice and recall work best once there is a basic grasp of each topic.
- Removing all feedback. Struggling without ever checking answers can lock in mistakes.
- Making everything hard. Some fluent study, such as a first read of new material or worked examples, is still useful as a starting point.
- Testing immediately afterwards. A quiz straight after a session measures performance, not learning. Leave a gap of at least a day.
The 15-minutes-a-day version
Desirable difficulties suit short sessions well, because spacing is built in. A simple daily pattern: spend five minutes recalling yesterday’s material from memory (write or say it), five minutes on new material, and five minutes on a mixed set of questions or problems from earlier in the week. Once a week, use the slot for the delayed quiz instead. Tools such as spaced repetition can handle the scheduling automatically if keeping track manually feels like too much.
How to measure progress
Because the whole point is that feelings mislead, measurement matters more here than with most methods.
- Delayed quiz scores: taken at least a few days after study, tracked weekly.
- Recall accuracy on first attempt: the share of recall questions answered correctly before checking.
- Transfer: success on problems or situations in a slightly new form, not just repeats.
- Confidence calibration: before each quiz, predict the score. Over time, predictions should get closer to results.
A simple log with four columns (date, topic, predicted score, actual score) is enough. After a month, glance down the columns: rising actual scores show learning, and a narrowing gap between the two columns shows sharper self-assessment. Both are worth more than a record of hours studied.
Calibration is an underrated signal. Learners who rely on fluency tend to overestimate what they know. Seeing the gap between predicted and actual scores shrink is evidence that judgement about learning is improving too.
Frequently asked questions
What are desirable difficulties?
They are study conditions that make practice feel harder or slower but tend to improve longer-term memory and transfer. Common examples are retrieval practice, spacing, interleaving and varied practice.
Who came up with the term desirable difficulties?
The term is associated with memory researchers Robert Bjork and Elizabeth Bjork, who studied the difference between performance during practice and lasting learning.
Is any hard study a desirable difficulty?
No. Difficulty only helps when the effort is aimed at the material and the learner can succeed with effort. Confusing instructions or distractions are just obstacles.
Why does effective study feel ineffective?
People judge learning by fluency. Methods that require recall or choice reveal gaps, which feels worse in the moment even when it strengthens later memory.
Should beginners use desirable difficulties?
Yes, with care. Beginners may need some initial study or worked examples first, then add recall, spacing and mixing as they gain a basic grasp.
How can I tell if a desirable difficulty is working?
Use delayed tests taken days after study, and compare them across weeks. How a session felt is not a reliable guide.
Do desirable difficulties apply to physical skills?
Research on motor learning shows similar patterns, especially for variation and spacing. Practising in varied conditions often transfers better than identical repetition.
Is rereading useless?
Not useless, but often less efficient than recall. A first read or a quick review after recall can help; repeated rereading as the main method tends to produce fluency without durable memory.
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This article was drafted with AI assistance and reviewed by the Life Learning Journey editorial team. Read our editorial standards.