Interleaving:
Why mixing topics works
Practicing one skill until perfect feels productive—but mixing skills produces better learning.
What is Interleaving?
Interleaving means mixing different topics, problem types, or skills during practice, rather than focusing on one type until mastery (blocking).
Instead of practicing 20 quadratic equations, then 20 linear equations, you mix them: quadratic, linear, quadratic, linear, and so on.
Like spacing, interleaving feels less effective in the moment—you make more errors during practice. But test performance is significantly better compared to blocked practice.
Blocked vs. Interleaved Practice
Same material, different sequencing
AAAA → BBBB → CCCC
ABC → BCA → CAB → ABC
All quadratic equations, then all linear
Mixed: quadratic, linear, quadratic, linear
Study Chapter 1, then Chapter 2, then Chapter 3
Mix problems from all chapters together
Practice one skill until mastery, then move on
Rotate between skills each practice session
Why Does Interleaving Work?
Discrimination learning
Mixing forces you to notice what makes each problem type unique, improving your ability to identify the right approach.
Spacing built in
When you interleave topics, you automatically space practice on each one—gaining spacing benefits too.
Better transfer
Real exams mix problem types. Interleaved practice matches the conditions you'll face.
Deeper encoding
The extra effort of switching contexts leads to more durable memory traces.
How Cruxly Implements Interleaving
When you study in Cruxly, questions from different topics and quizzes are intelligently mixed.
You won't just drill one topic until you're bored—the algorithm interleaves material to maximize learning efficiency. Different question types, different topics, different difficulty levels—all mixed to create optimal challenge.
Combined with spaced repetition, this creates a study experience that feels natural but incorporates decades of learning science.
FAQ
Why does interleaving feel harder?
Because it IS harder—you can't rely on the same approach repeatedly. This extra effort is a desirable difficulty that strengthens learning. Blocking feels smooth but produces weaker retention.
When should I use blocking vs. interleaving?
Use blocking when first learning a completely new skill (you need the basics). Switch to interleaving once you have some competence. Most students switch to interleaving too late.
Does interleaving work for all subjects?
It's most studied in math and motor skills, but research shows benefits across subjects. Anywhere you need to discriminate between similar concepts or procedures, interleaving helps.
How much mixing is optimal?
There's no perfect formula. The key is to mix enough that you have to think about which approach to use. If you're always certain what type of problem you're facing, add more mixing.