Desirable difficulties are study conditions that feel harder in the moment but produce significantly better long-term memory than easier alternatives. The core finding: the revision strategies that feel most productive — re-reading, cramming — are typically the least effective, while testing yourself and spacing sessions are among the most powerful.
Where does the idea of desirable difficulties come from?
The term was coined by cognitive psychologist Robert Bjork in the 1990s to describe a set of conditions that introduce difficulties into learning which are "desirable" because they enhance long-term retention and transfer of knowledge, even though they slow initial acquisition. The distinction is crucial: a difficulty is desirable if the struggle during learning produces better outcomes later. A difficulty is undesirable if it simply makes learning harder without benefit — for example, studying in a noisy room that prevents concentration.
Bjork's framework emerged from research on memory that consistently found a disconnect between how productive a study technique feels at the time and how much it actually produces. Students rate re-reading as their most common and preferred revision strategy. Research consistently rates it as one of the least effective — precisely because it feels easy and familiar, which creates a false impression of mastery.
What are the main desirable difficulties?
1. Spaced practice — Studying material across multiple sessions spread over days or weeks, rather than in one concentrated block. The difficulty: you are more likely to have partly forgotten the material when you return to it. The benefit: the effortful retrieval of partly-forgotten material produces much stronger memory traces than reviewing material that is still fresh.
2. Retrieval practice — Testing yourself on material rather than re-reading it. The difficulty: actively recalling information from memory is harder than recognising it when you see it written down. The benefit: the act of retrieval itself strengthens memory, not just the re-reading that confirms it. The EEF's teaching and learning toolkit identifies retrieval practice as one of the highest-impact strategies in education.
3. Interleaving — Mixing up different topics or problem types within a single study session, rather than completing all of one topic before moving to the next. The difficulty: interleaving feels more confusing and less productive than blocking (completing one topic at a time). The benefit: interleaving improves the ability to discriminate between different problem types and select the right approach under exam conditions — exactly what most exam questions require.
4. Generation — Attempting to produce an answer or solution before being shown it, even when you are not confident. The difficulty: generating an answer and being wrong feels inefficient. The benefit: the attempt to generate an answer, even an incorrect one, enhances subsequent learning from the correct answer compared to simply reading the answer immediately.
5. Varying the conditions of study — Studying in slightly different environments, at different times of day, or from slightly different angles on the same topic. The difficulty: varied practice feels less orderly than consistent practice. The benefit: varied practice builds more flexible, context-independent knowledge that transfers better to an exam setting than knowledge tied to a single study routine.
Why does difficulty improve memory?
The cognitive explanation involves the concept of encoding strength. When retrieval is easy — because the material is very fresh, very familiar, or very similar to what was just reviewed — the memory trace that retrieval leaves behind is weak. When retrieval requires effort — because there has been a gap, the question is slightly different, or the material is being approached from a new angle — the memory trace is significantly stronger.
This means the uncomfortable feeling of struggling to remember something during retrieval practice is not a sign that learning is going badly. It is a sign that learning is going well. The struggle is the mechanism; the effort is the learning.
What does this mean in practice for a KS3 or GCSE student?
| Less effective but feels productive | More effective but feels harder |
|---|---|
| Re-reading notes repeatedly | Closing notes and retrieving from memory |
| Studying one topic for two hours in one session | Spreading the same content over three sessions |
| Completing twenty maths problems of the same type | Mixing problem types within a session |
| Reading the model answer before attempting the question | Attempting the question first, even imperfectly |
| Revising in the same environment at the same time every day | Occasionally varying location and time |
Making this switch is psychologically difficult. Easier strategies feel more productive because fluency feels like mastery. But the feeling of learning and the reality of long-term retention are not the same thing. Metacognition — the ability to accurately monitor your own understanding rather than relying on how revision feels — is exactly the skill the EEF identifies as one of the highest-leverage academic skills available to secondary students.
How do you introduce desirable difficulties into your revision without overwhelming yourself?
Start with two changes:
- Replace one re-reading session per week with a retrieval session. Close your notes, write down everything you know about a topic, then check and fill the gaps. Do this once per subject per week.
- Add a gap before reviewing difficult material. Instead of going back to something you found hard immediately, wait a day. The extra forgetting makes the review more effortful — and more effective.
Once these feel natural, introduce interleaving into your maths and science practice: do not complete ten trigonometry questions and then ten quadratics — mix them from the start of the session.
Frequently asked questions
Does this mean easy revision methods are always wrong?
Not exactly. Some easier techniques serve specific purposes: re-reading is reasonable for initial exposure to very new material; highlighting can help identify what to prioritise; revision videos are useful for understanding context. The problem arises when these techniques dominate revision, crowding out the retrieval and spacing that produce durable memory. Think of easier techniques as reconnaissance and the desirable difficulties as the actual learning.
How do I know if a difficulty is desirable or just making things unnecessarily hard?
A desirable difficulty produces better long-term outcomes despite slowing short-term acquisition. An undesirable difficulty (such as a noisy environment, ambiguous questions, or material that is entirely beyond your current level) impairs both short-term acquisition and long-term retention. The key test: does the difficulty require you to engage more deeply with the material, or does it prevent you from engaging at all? The former is desirable; the latter is not.
Is desirable difficulty the same as challenging yourself?
Partly. Desirable difficulties are specific, research-identified conditions — spacing, retrieval, interleaving, generation, variation. General "challenge" without these features (for example, choosing a harder revision guide to feel more serious) does not reliably produce the same benefits. The term is specific to these evidence-based conditions.
Why do students prefer easy revision methods if harder ones work better?
Because human beings consistently prefer fluency over effort, and because the benefit of difficult learning only appears later — at the test or exam — while the effort appears immediately. Students who re-read notes feel confident after the session because the material feels familiar. Students who test themselves often feel uncertain after the session because retrieval exposed the gaps. The feeling of confidence is mistaken for the reality of learning. Research consistently shows that the self-testing group performs significantly better at actual tests, despite feeling less confident immediately after the revision session.
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