Picture this: you have exams in three different classes next week. So you do what every logical student does — you dedicate Monday night to biology, Tuesday to statistics, and Wednesday to psychology. One subject per session. Clean. Organized. Satisfying.
And completely suboptimal.
There's a study technique that cognitive scientists have been raving about for over a decade, but almost no students use it. It's called interleaving, and it flips everything you think you know about study sessions on its head.
Interleaving means mixing different subjects or problem types within a single study session instead of focusing on one topic until you feel "done" before moving to the next.
So instead of spending three hours on biology, you'd spend 30-40 minutes on biology, switch to statistics for 30-40 minutes, move to psychology, and then cycle back. Same total study time. Radically different results.
It sounds counterintuitive. It feels less productive. And that's exactly why it works so well.
A landmark study by Rohrer and Taylor (2007) tested interleaving with math problems. One group of students practiced by completing blocks of similar problems in a row (the way most of us study). The other group practiced the same problems, but they were shuffled randomly.
On the practice session itself, the blocked group performed better. They were faster and more accurate. But on the test a week later? The interleaved group scored 43% higher.
Read that again. The group that felt worse during practice absolutely crushed the group that felt confident. This pattern has been replicated dozens of times across subjects — math, science, art, music, medical diagnosis, even sports training.
The reason is something researchers call "desirable difficulty." When studying feels slightly harder — when you have to work a little to remember which formula applies or which concept you're using — your brain encodes the information more deeply. Blocked practice feels smooth because your brain doesn't have to make decisions. Interleaved practice forces your brain to constantly retrieve, compare, and discriminate between different concepts.
That's exactly what an exam requires you to do.
When you study biology for three straight hours, you build a kind of short-term fluency. By the end of the session, you can rattle off definitions and recognize concepts immediately. This fluency feels like learning. It's not.
It's recognition, and recognition is not the same as recall. On an exam, nobody shows you a concept and asks "do you recognize this?" They give you a problem and expect you to figure out which concept applies and how to use it.
Blocked studying trains recognition. Interleaved studying trains discrimination and retrieval — the actual skills you need on test day.
This is also why students so often say "I knew it when I studied it, but I blanked on the test." They did know it — in the context of a blocked study session where the topic was obvious. Remove that context, and the knowledge falls apart.
Interleaving doesn't mean chaotically jumping between subjects every five minutes. There's a practical structure that works for most students.
Start with 25-40 minute blocks per subject. Use a timer. When the timer goes off, switch — even if you're not "done" with the topic. This is important. The slight frustration of switching mid-flow is part of what makes it effective.
Within a single session, rotate through 2-3 subjects. If you're studying for one subject, interleave different types of problems instead. In statistics, alternate between probability questions, hypothesis testing, and regression problems rather than doing all of one type before moving on.
Keep a brief note when you switch: write down where you left off and one thing you want to revisit. This takes 30 seconds and prevents the "where was I?" friction when you cycle back.
Here's where having organized study material matters enormously. If your notes are scattered across multiple documents, PDFs, and random screenshots, switching between subjects becomes an organizational nightmare instead of a cognitive exercise. Tools like Snitchnotes can solve this — upload your lecture material for each class and get clean, structured notes with practice quizzes ready to go. When switching between bio and stats is as simple as opening a different set of notes, interleaving becomes genuinely seamless.
Fair warning: the first time you try interleaving, you'll feel like you're learning less. Your practice accuracy will drop. You'll feel scattered. You'll be tempted to go back to blocking because it's more comfortable.
Don't. The research is unambiguous. The initial discomfort is the learning happening. Students who push through the awkward first week consistently report that after 7-10 days, interleaving starts to feel natural — and their test scores reflect the difference.
Interleaving isn't always the answer. If you're encountering material for the very first time and have zero foundation, spend a focused session building basic understanding before you start interleaving. You need to understand the basics of a concept before you can meaningfully discriminate between it and other concepts.
The sweet spot is interleaving during review and practice, once you have at least a surface-level grasp of each topic. That's when the mixing forces your brain to do the heavy lifting that translates to exam performance.
You don't need to study more. You need to study in a way that mirrors how exams actually test you — with mixed problems, no context cues, and decisions about which tool to use.
Interleaving gives you that. It's harder in the moment, but it's dramatically more effective when it counts.
Try Snitchnotes for free at snitchnotes.com and make switching between subjects effortless.
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