Interleaving vs. Blocking: The Study Strategy That Changes How Well You Retain What You Learn

When you’re trying to learn something new, it’s tempting to focus on one topic at a time.

“Today is all Chapter 3.”
“I’ll finish all the vocabulary before moving on.”
“Let me do 50 algebra problems in a row.”

It feels structured. It feels productive. It feels efficient.

But learning science shows that how you sequence your study sessions can dramatically influence how well you retain and apply what you learn.

Two primary strategies dominate study habits, blocked practice and interleaved practice. Understanding the difference, and knowing when to use each, can transform the way you learn.

What Is Blocked Practice?

Blocked practice means focusing on one topic completely before moving to the next. For example, you might review an entire chapter in a single sitting, complete only one type of math problem repeatedly, or practice a single skill again and again before moving on.

In sports, this looks like practicing only free throws before switching to layups. In music, it might mean repeating one scale over and over before practicing another.

Blocked practice highlights similarities within a category. Because the same strategy stays active in your mind, performance improves quickly and feels smooth. This often creates a strong sense of mastery.

The challenge, that feeling can be misleading.

What Is Interleaving?

Interleaving means mixing different topics or problem types within the same study session. Instead of working through Topic A repeatedly before moving to Topic B, you rotate between topics in a pattern such as A, B, C, then back to A.

For example, you might alternate between algebra, geometry, and word problems in a single session. You might mix vocabulary review with reading comprehension practice. A musician might rotate through multiple scales instead of isolating just one. You could also blend conceptual questions with applied scenarios rather than separating them.

Interleaving forces your brain to repeatedly identify the problem type, retrieve the correct strategy, and apply it appropriately. It feels harder, and that is exactly why it works.

Why Interleaving Works

1. It Creates Desirable Difficulty

Switching between topics increases cognitive effort. Your brain must determine what kind of problem it is facing, recall the correct method or concept, and apply it accurately. Psychologists call this desirable difficulty. The added effort strengthens neural connections and improves long-term recall (Hulbert & Norman, 2014).

Harder during practice equals stronger later.

2. It Improves Concept Differentiation

Real-world learning rarely presents neatly labeled categories. You often must quickly recognize what type of problem you are facing, how it differs from similar problems, and which strategy applies.

Research shows that interleaving improves discrimination between similar categories (Carvalho & Goldstone, 2014). When topics are mixed, your brain learns to notice subtle differences rather than rely on repetition alone.

Blocked practice highlights similarities. Interleaving highlights differences. That difference strengthens flexible thinking.

3. It Strengthens Long-Term Retention

Decades of research across domains, from sports to medicine to mathematics, show that interleaving improves delayed performance. Athletes trained with interleaving demonstrate better long-term skill retention (Goode & Magill, 1986). Students better distinguish complex visual styles when study is interleaved. In a large classroom math study, interleaving led to significantly higher test scores after one month compared to blocked homework (Rohrer & Taylor, 2007).

The advantage grows over time. Interleaving does not just improve practice performance, it improves lasting performance.

The Illusion of Mastery

One of the most important insights from learning science is this: how learning feels during practice does not predict how well it will last.

Blocked study often feels smooth, produces high immediate accuracy, and builds confidence quickly. Interleaving often feels effortful, may reduce short-term accuracy, and requires more concentration. Yet on delayed tests, interleaving frequently leads to equal or superior performance.

That mismatch is called the illusion of mastery. Smooth practice can create confidence without creating durable memory. Difficulty during learning often signals deeper processing.

When Blocking Helps

Interleaving is powerful, but not always ideal at the beginning. Blocked study is especially helpful when you are first building foundational understanding, when terminology or processes are brand new, or when you need structure to reduce overwhelm.

Blocking builds the framework and reduces cognitive load while you are still learning core ideas.

When Interleaving Helps Most

Interleaving becomes especially effective when you need to distinguish between similar concepts, when you are preparing for cumulative assessments, when you must apply knowledge flexibly, or when the environment will be unpredictable.

In real-world situations, information is rarely presented in neat sections. Problem solving requires switching between ideas and recognizing subtle differences. Interleaving mirrors those real conditions.

A Balanced, Research-Based Approach

The strongest strategy is not all blocking or all interleaving. A balanced approach works best. Start with blocking to build foundational understanding. Gradually introduce interleaving as familiarity increases. As you move toward application and mastery, emphasize mixed practice.

This progression moves you from recognition-based learning to flexible, durable application.

How to Use Interleaving in Your Study Plan

You do not need to overhaul your routine. Start small. Instead of spending several hours on a single topic, divide your session into segments, such as 45 to 60 minutes on one topic, followed by another segment on a different topic, then returning later to review weaker areas.

You can also rotate multiple topics within a single session rather than isolating one subject at a time. Even within one subject area, you can mix problem difficulty levels, rotate between conceptual and applied questions, and alternate formats or conditions.

Combining interleaving with spaced repetition further strengthens learning. Spacing involves reviewing material over increasing intervals of time, while interleaving involves mixing topics within a session. Together, they significantly strengthen retention and application.

Common Mistakes to Avoid

Interleaving requires balance. Switching topics every few minutes can make studying feel fragmented and unproductive. Rushing through material without fully understanding it undermines the benefit. Completely abandoning older topics eliminates the comparison effect that makes interleaving powerful.

Consistency and thoughtful sequencing matter more than constant switching.

The Bottom Line

Interleaving requires no extra study time, no special tools, and no complicated system. It requires only thoughtful sequencing.

If your study sessions feel slightly harder after you begin mixing topics, that is not a warning sign. It may be evidence that you are building stronger, more durable learning.

The way you organize your study time is not just a preference. It is a powerful lever that shapes retention, discrimination, and long-term performance.

The difficulty you feel might be doing the real work.

References

Carvalho, P. F., & Goldstone, R. L. (2014). Effects of interleaved and blocked study on delayed test of category learning generalization. Frontiers in Psychology.

Goode, S. & Magill, R. A. (1986). Contextual Interference Effects in Learning Three Badminton Serves.

Hulbert, J. C., & Norman, K. A. (2014). Neural differentiation tracks improved recall of competing memories following interleaved study and retrieval practice. Cerebral Cortex.

Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481–498.

Pan, S. C. (2015). The Interleaving Effect: Mixing It Up Boosts Learning. Scientific American.

University of Arizona (2019). L2L Strategy – Interleaving. Academic Affairs.

Ferlazzo, L. (2021). The What, Why, and How of Interleaving. Education Week.