The Power of Interleaving: Why Mixing It Up Might Just Be the Best Way to Learn
Focusing on one topic doesn't foster mental connections between concepts
by Jacob McGregor, PharmD, PGY1 Pharmacy Practice Resident, University of Mississippi Medical Center
Ever notice that learners may ace an exam one day and forget everything they learned the next? That’s because traditional “blocked learning” – focusing on one topic at a time before moving to the next – might not be as effective as you think. A different way of teaching and learning has begun to emerge, known as interleaving: a strategy that involves alternating between different topics or problem types in a single session. This is a technique every educator and student can use to help strengthen retention, deepen understanding, and apply knowledge more flexibly. And honestly, life is more like interleaving than blocking – we all juggle multiple responsibilities at once.
What is Interleaving?
Interleaving is all about mixing things up – asking learners to shift between different topics or skills rather than drilling one idea repeatedly. Let’s take health professional students preparing for a pharmacology exam (it’s what I know best). Instead of guiding the students to memorize fifty drug names in one go, you may encourage them to alternate between learning about mechanisms of action, brand names, and disease state management. It may help to think of interleaving as a “mental workout” of sorts. It won’t do much good for your physical health if you only go to the gym and do only bicep curls. Instead, interleaving provides a broad range of workouts that are, whether we are talking about physical or mental fitness, beneficial to your overall success.
One study showed that introducing interleaving into your coursework not only improves attention and reduces cognitive overload but also enhances learning outcomes when different modalities, such as visual and auditory learning, are combined.1 That’s because interleaving forces the learner’s brain to stop, differentiate, and understand concepts rather than just recognize patterns. Block learning may be a good method to prepare for a test tomorrow, but it's terrible for long-term retention.
Why Does Interleaving Work?
Here are the key reasons why interleaving works:
It creates desirable difficulty. To your learners, interleaving feels harder, and that’s actually a good thing. When learning is too easy, your brain is trained to go into “autopilot” mode rather than putting in the effort to assimilate information and make a variety of connections between different concepts. Interleaving forces learners to process material actively rather than passively recognizing patterns.
It improves long-term retention. Cramming might save a test score tomorrow, but interleaving builds knowledge that lasts. One study observed that interleaving improved the long-term retention and application of learned material.2 The study compared two different learning strategies: interleaving vs. blocked learning. Students who learned in an interleaving manner recalled more relevant information and produced more frequently correct solutions on two surprise tests when compared to students who learned using a traditional blocked learning method. But here's the really interesting part. The students found interleaving to be undesirable, and they perceived they learned less, even though their test results showed otherwise. This highlights that interleaved learning feels uncomfortable, at least at first, until learners develop an efficient system.
It reduces the illusion of mastery. Blocked learning often tricks students into thinking they’ve mastered material when they’ve only memorized surface patterns. One example from my personal experience where learners may fall prone to this false sense of mastery is pharmacokinetics mathematics. Learners can grow comfortable practicing twenty math problems to learn the pattern of pharmacokinetics equations, but in the real world, when they encounter a patient who does not fit the pattern, they get erroneous answers. Encouraging interleaved learning in your classroom can be of assistance here. You may encourage learners to alternatively practice math problems and then switch lanes to learn about pharmacokinetic parameters (e.g. absorption, distribution, metabolism, excretion), all within the same study session. This method helps learners process each component individually, make connections between related (but different) concepts, and prepare them to apply knowledge flexibly to real-world scenarios.
How Educators Can Implement Interleaving
The good news? Interleaving is easy to integrate into existing lesson plans – and doesn’t require a complete redesign of your course. Some ideas:
Mix topics within a session. Instead of focusing exclusively on one concept (e.g., diabetes management), blend cases involving hypertension, hyperlipidemia, and diabetes. This forces learners to differentiate and apply knowledge from interrelated concepts.
Mix up problem types. Within pharmacokinetics, don’t just assign standard dosing calculations. Throw in altered renal function, different drug formulations, or disease state complications.
Shuffle practice materials. Rather than grouping practice questions by topic, create mixed sets of topics. This forces the learner’s brain to work harder to switch lanes of different concepts and recall information more efficiently.
Embrace the discomfort. Interleaving can frustrate learners initially as it takes them out of the traditional method of learning and forces them to work harder. That is exactly why it works. Normalize that discomfort as a healthy sign of cognitive effort.
Some additional examples include:
Create quizzes that include several different question styles.
Design lectures that combine varying yet somewhat concepts, such as Type 1 Diabetes Mellitus (a disease process of hormone underproduction) and Hyperthyroidism (a disease process of hormone overproduction).
Build case questions that require the learner to consider multiple outcomes by comparing them. One example I have used during a lecture I gave is posing the question, “What from the patient case indicates that signs and symptoms from disease state X are not attributed to another cause?” This question encourages the learner to compare and contrast what they’ve learned previously.
Use multiple learning resources to integrate auditory, visual, and hands-on learning.
Beyond the Classroom: Interleaving for Real-World Readiness
Providing healthcare demands rapid task-switching and flexible decision-making skills that traditional blocked learning may not foster. Interleaving better prepares learners for the unpredictable realities they’ll face.
Pharmacists review patients’ drug therapy regimens to improve clinical decision-making by distinguishing treatment courses for multiple disease processes.
Nurses learn to prioritize care concerns for patients with competing needs.
Physicians must learn diagnostic reasoning across different organ systems in a single shift.
Final Thoughts
Interleaving might not feel as satisfying as blocked practice, but it’s one of the best ways to meaningfully learn rather than memorize. By challenging learners to stretch across topics and problem types, educators can move students from surface-level familiarity with patterns to real-world competence. So, the next time you plan a lecture or design a quiz, try to resist the temptation to keep things linear. Mix it up – because sometimes, the best way to teach isn’t by keeping things neat but by keeping it real.
References:
Chen W, Chen C, Li B, Zhang J. Applying Interleaving Strategy of Learning Materials and Perceptual Modality to Address Secondary Students' Need to Restore Cognitive Capacity. Int J Environ Res Public Health. 2022;19(13):7505.
Samani J, Pan SC. Interleaved Practice Enhances Memory and Problem-Solving Ability in Undergraduate Physics. NPJ Sci Learn. 2021;6(1):32.