Interleaving is an evidence-based learning technique where students mix, or interleave, multiple subjects or topics while studying in order to improve learning outcomes.

What is Interleaving?

Interleaving is a learning approach that involves mixing different topics, concepts, or problem types within a single study session, rather than focusing on just one topic at a time (known as "blocked practice"). For example, instead of practicing 20 algebra problems, then 20 geometry problems, and then 20 statistics problems, an interleaving approach would mix these problem types throughout the practice session.

This technique creates a more challenging learning environment initially, but research shows it leads to better long-term retention and skill transfer compared to traditional blocked studying methods.

How Interleaving Works

Interleaving works by forcing the brain to continually retrieve and select the appropriate strategy for each problem type. This process strengthens memory associations and helps students develop better discrimination skills between different concepts. The cognitive effort required during interleaving enhances long-term learning in several ways:

  • Improved Discrimination: Helps students better distinguish between similar concepts or problem types
  • Enhanced Retrieval Practice: Creates more opportunities for memory retrieval, strengthening neural pathways
  • Context Variability: Exposes learners to material in different contexts, improving transfer of knowledge
  • Desirable Difficulty: Introduces productive challenges that enhance long-term retention

Interleaving vs. Blocked Practice

Blocked Practice Example: Studying chapter 1 completely, then moving to chapter 2, then chapter 3.

Interleaving Example: Studying key concepts from chapters 1, 2, and 3 in a mixed sequence, returning to each topic multiple times.

Practical Examples of Interleaving

  • Mathematics: Mix problems requiring different formulas or procedures (e.g., alternating between algebraic equations, geometry problems, and calculus concepts)
  • Language Learning: Practice different grammar rules, vocabulary themes, and conversational contexts within the same study session
  • Science: Mix questions about different scientific principles or methods rather than focusing on one topic at a time

Benefits and Challenges

Benefits

  • Enhances long-term retention
  • Improves ability to discriminate between concepts
  • Develops better problem-solving skills
  • Promotes deeper understanding of material
  • Better prepares students for exams and real-world applications

Challenges

  • Initially feels more difficult and less productive
  • May temporarily decrease performance during learning
  • Requires more planning and preparation
  • Can be frustrating for students accustomed to blocked practice
  • May not be suitable for absolute beginners in a subject

How to Implement Interleaving

  1. Start with related concepts: Begin by interleaving related but distinct topics or problem types
  2. Create mixed problem sets: Prepare study materials that combine different types of questions or concepts
  3. Space out repetition: Return to previously studied material at increasing intervals
  4. Combine with other effective techniques: Use interleaving alongside retrieval practice, spaced repetition, and elaboration
  5. Balance with some blocked practice: Use blocked practice for initial learning, then transition to interleaving

Research Support

Numerous studies have demonstrated the effectiveness of interleaving. For example, a 2010 study by Rohrer and Taylor found that students who practiced math problems in an interleaved manner performed 63% better on a delayed test compared to students who used blocked practice. Similarly, research in motor skill learning, language acquisition, and concept learning has consistently shown advantages for interleaved practice.

While interleaving may initially feel less productive (a phenomenon known as "desirable difficulty"), the additional cognitive effort it requires leads to stronger, more durable learning in the long run.

When to Use Interleaving

Interleaving is most effective when:

  • Learners have established some basic understanding of the individual topics
  • The goal is long-term retention rather than immediate performance
  • The material involves discriminating between similar concepts or procedures
  • Preparing for comprehensive exams covering multiple topics
  • Developing flexible, adaptable skills that transfer to new situations

By incorporating interleaving into your study routine, you can transform learning from a temporary memorization exercise into a process that builds lasting knowledge and transferable skills.