The Cognitive Science Behind Interleaving and Its Impact on Learning
For the critical evaluator, the idea of mixing up different subjects or topics during a single study session can seem counterintuitive. Our instincts tell us to focus on one thing at a time, to “block” our study sessions by subject. But what if this seemingly logical approach is actually less effective for long-term retention? This is the central question addressed by the cognitive science behind interleaving, a powerful memorization technique for studying that challenges traditional study methods.
Interleaving is the practice of mixing different types of problems or topics within a single study session. For example, instead of practicing 20 math problems of the same type, you would practice a few problems of different types, switching between them. At first, this can feel slower and more difficult. The constant switching forces your brain to work harder, retrieving a different mental model for each new problem. This “desirable difficulty” is precisely why it is so effective.
The scientific evidence overwhelmingly supports interleaving over blocking for building long-term memory and problem-solving skills. When you study in blocks, your brain can fall into a rhythm, using the same neural pathways repeatedly. It’s a form of passive practice. When you interleave, your brain is forced to:
- Discriminate: You must first identify the type of problem you are facing before you can apply the correct solution. This process of identifying the correct strategy is a crucial skill for test-taking and real-world application.
- Retrieve: Each time you switch to a new topic, you are engaging in a form of active recall, retrieving a different set of information from your long-term memory. This effort strengthens those neural pathways.
- Contrast: Interleaving allows you to see the differences and similarities between concepts, building a more flexible and robust understanding of the material.
A number of studies have demonstrated the power of interleaving. In one experiment, students who learned a skill by practicing it in an interleaved fashion performed significantly better on a final test compared to students who practiced the skill in a blocked manner, even though the interleaved group felt like they were learning more slowly. This is a classic example of how our subjective feeling of learning can be misleading. By incorporating interleaving into your study routine, you are transforming your brain into a more flexible and adaptable learning machine. You’re not just memorizing isolated facts; you’re building a network of interconnected knowledge that is readily accessible and applicable in a variety of contexts.
Common FAQ about Interleaving
1. Is interleaving just for math? No. It can be applied to many subjects. For a history class, you could study different historical periods or events in a single session. For a language, you could practice a mix of vocabulary, grammar, and pronunciation.
2. How is this different from multitasking? Multitasking involves doing several things at once, which is generally inefficient. Interleaving is a strategic, sequential process of switching between different types of learning tasks to improve understanding and retention.
3. Will interleaving make my study sessions longer? Initially, it may feel that way because it requires more cognitive effort. However, it leads to better long-term retention, reducing the need for repeated review and saving you time in the long run.
4. Can I interleave completely new subjects? Interleaving is most effective for related but distinct subjects or topics. For example, you wouldn’t interleave studying for a biology exam with learning a new piece of music. Interleaving works because it forces you to compare and contrast related concepts.
5. What is the “desirable difficulty” in this method? The desirable difficulty is the cognitive effort required to switch between different topics. This effort, while challenging, is what leads to deeper learning and more durable memories.
6. Does interleaving mean I should never study in blocks? No. A good strategy is to learn a new concept in a block until you have a basic understanding, and then begin to interleave it with other concepts you’ve learned.
7. How do I start using interleaving? Start small. The next time you sit down to study, practice a few problems from each of the last two chapters instead of just focusing on the current one.
8. Is there a downside to this method? The main “downside” is that it can be psychologically challenging. You may feel like you’re not making progress as quickly as you would with blocking, but you have to trust the science and know that you’re building a much stronger foundation.
9. What if the topics are too different? Interleaving is not for completely unrelated subjects. It is most effective when the topics are related enough to be confused, as the act of discriminating between them is what strengthens the memory.
10. What’s the main takeaway about interleaving? Interleaving is a powerful, science-backed study strategy that moves beyond simply memorizing facts. It builds the skill of knowing which tool to use for which job, creating a flexible and applicable knowledge base.