Interleaving
Switch topics before mastery to keep the brain uncomfortable
- Difficulty
- Moderate
- Time to result
- ~weeks to results
- Steps
- 4
- Confidence
- 88%
Interleaving means deliberately mixing different topics or exercises within a single study or practice session rather than blocking one skill until it feels mastered. The mechanism relies on desirable difficulty: the moment you feel the pleasant 'I've got this' sensation, you are no longer really learning, so you switch to something else just as you approach mastery. This keeps the brain in its zone of discomfort, which maximises learning per unit time. Ali cites hockey-coaching studies (via Make It Stick) and David Epstein's Range, which pairs testing, spacing and interleaving as the three primary drivers of learning any skill. Interleaving is best used as the tool that injects difficulty once a topic is no longer new enough to be hard on its own.
Origin
Drawn from Make It Stick's hockey-coaching studies and David Epstein's Range. Ali Abdaal applies it as the mechanism for forcing productive discomfort into study sessions.
Core principles
- 01Comfort is the signal that learning has stopped
- 02Mixing topics forces the brain to stay effortful
- 03Blocked practice on one thing feels good but teaches less
- 04Interleaving is the tool that forces discomfort into learning
- 05Skip interleaving when a topic is already hard enough on its own
How to run it
- 1
Assemble a mixed session
Choose several different topics or exercise types to rotate through in one sitting rather than a single subject.
Pro tip Example: mix a bit of cardiology, a bit of haematology and a biochemistry pathway in one session.
- 2
Work each topic to the edge of comfort
Engage with a topic until you feel yourself beginning to get the hang of it and starting to enjoy it.
Watch out Do not chase the mastery sensation; that feeling is the point at which learning slows.
- 3
Switch on the verge of mastery
As soon as that comfortable feeling arrives, switch completely to a different topic and repeat.
Pro tip It should feel slightly annoying; that annoyance is the brain being kept effortful.
- 4
Gate it on difficulty
For a brand-new topic you are struggling with, skip interleaving; only introduce variety once the material is comfortable enough to need extra challenge.
In the wild
Ali recounts the Make It Stick finding on hockey coaching. Coaches get the best results not by drilling one exercise to mastery, but by switching to a completely different exercise just as players are on the verge of getting it. As soon as players start to feel competent at the new drill, the coach switches again. Players find it annoying because they never get the satisfying mastery sensation, but precisely because the brain is never allowed to settle, they learn faster and retain more than under blocked, one-drill-at-a-time practice.
→ Faster skill acquisition and better retention than comfortable blocked practice.
Common mistakes
Chasing the mastery feeling
Staying on a topic because it now feels good keeps you in low-value repetition; that comfort is the cue to switch away.
Interleaving a brand-new topic
Adding variety to material you barely grasp overloads you; a genuinely new topic is already difficult enough without switching.
Is it for you?
Best for
Consolidating topics you already partly understand and want to strengthen efficiently across a study session.
Not ideal for
A brand-new topic you are still struggling to grasp, where the difficulty is already high enough.
From the transcript
“as soon as I start feeling that feeling of oh okay I'm quite enjoying this at that point I switch tasks”
“the interleaving is the tool with which you force the discomfort into the learning process”
From the episode
How To Learn & Remember Anything, Fast - Ali Abdaal - #231
Ali Abdaal