Desirable Difficulties & Interleaving:
Why making learning slightly harder helps your child remember more!
When parents watch their child revise, they often see two extremes:
- revision that looks too easy - lots of reading, highlighting, watching videos
- revision that looks too hard - overwhelm, frustration, “I don’t get any of this”
Neither of these leads to strong learning.
There’s a sweet spot in the middle, a level of challenge that makes the brain work just enough to build long‑term memory without overload. In cognitive science, we call this desirable difficulty.
And when you combine desirable difficulty with interleaving, mixing topics instead of studying one thing for a long stretch, you get one of the most powerful revision approaches available to students.
This article explains what desirable difficulties are, why they matter, and how you can help your child use them at home.
THE BIG IDEA
Cognitive scientist Daniel Willingham summarises decades of research in one sentence:
Memory is the residue of thought.
If your child isn’t thinking during revision, they won’t remember much afterwards. And this is why passive revision, such as reading notes, highlighting, copying, watching videos, feels productive but secures very little learning. The brain isn’t doing the kind of work that creates memory. Desirable difficulties fix this.
What are Desirable Difficulties?
A desirable difficulty is a small, intentional challenge built into learning. It’s not overwhelming, it’s simply requires effort.
Think of it like Goldilocks’ porridge:
- Too easy → no thinking → no memory
- Too hard → cognitive overload → meltdown
- Just right → effortful thinking → strong memory
When students revise in this “just right” zone, they remember more, for longer, with less re‑learning later.
How to build Desirable Difficulties into revision
The easiest way to create desirable difficulty is through active revision techniques that force the brain to retrieve, compare, and think.
Three of the most effective are:
1. Flashcards
A question or prompt on one side, the short answer on the other. They force retrieval the most powerful learning process we know.
2. Self‑quizzing
Look, cover, write (or say!), check. Simple, but incredibly effective. There's a reason primary school students use this to learn spellings.
3. Exam questions
Short questions, long questions, multiple choice - all of them require retrieval and application. These techniques feel harder than reading or highlighting, but that difficulty is desirable. It’s the difficulty that builds memory.
The Pomodoro Technique makes this even better
In the last article, we explored the Pomodoro technique:
- 25 minutes of focused work
- 5 minutes of rest
This structure is perfect for desirable difficulties because:
- 25 minutes is long enough to create challenge...
- ... and short enough to avoid overwhelm.
- And the break resets the brain before fatigue kicks in.
Within each 25‑minute block, your child should choose one active technique mentioned above.
Within the 5‑minute break, they should avoid anything that pulls attention too deeply.
Good breaks:
✅ stretching
✅ getting a drink or a snack
✅ quick walk around the garden
Not‑so‑good breaks:
❌ phones
❌ social media
❌ video gaming
❌ YouTube
❌ social media
❌ video gaming
❌ YouTube
Breaks should reset the brain, not overload it.
Interleaving: Adding challenge automatically
Interleaving means mixing topics instead of studying one thing for a long block. For example:
- 10 minutes electricity
- 10 minutes forces
- 10 minutes waves
Switching topics feels harder, but that difficulty is desirable. It strengthens long‑term memory and improves exam performance.
Interleaving also mirrors how exams work:
- questions jump between topics
- papers jump between subjects
- students must switch gears constantly
By practising this during revision, students become more flexible thinkers and more confident in the exam hall.
And the best part? You plan the mix before the session starts, and the desirable difficulty happens automatically.
How parents can help
- Encourage short, spaced revision sessions using active revision techniques.
- Help build a timetable that promotes interleaving (or use my Free 10-minute revision plan builder)
- Ensure revision includes regular purposeful breaks.
How Nebula Learning Lab helps
Nebula is built around making learning just challenging enough to be effective:
- Desirable difficulty is built into every lesson, with a range of active revision techniques - retrieval tasks, short quizzes and exam questions. This encourages thinking rather than just reading.
- With regular coaching calls and flashcard quizzes, we plan interleaving into your revision timetable.
- Lessons are designed to fit into a 25-minute Pomodoro slot.