When I first “heard” this term, like you, I couldn’t believe my eyes. I was reading Make It Stick by Peter C. Brown and his colleagues and was intrigued by the word itself—I mean, inter“weaving” makes so much more sense—so I started digging around online to see what others had to say. Most people were saying the same thing I was thinking, and many were just as surprised to learn that interleaving is not a new concept, having been discovered by physiology researchers in the 1960s (Benedict 90).

But, like you, I’m always up for learning something new!

Interleaving is the practice of teaching two or more skills in tandem (Brown 49), inter“weaved,” if you will. Interleaving is radical because it takes much of what we have been taught about teaching and revolutionizes our thinking. Interleaving is counter-intuitive because it is challenging for students to discern between concepts as they practice skills with which they are not yet familiar or have not yet mastered. Interleaving is pioneering and will require a significant shift in thinking but, fortunately, only minor shifts in instruction.

It’s Time to Get Radical!

Take, for example, a lesson on writing compound sentences.

  • A passionate teacher might follow grammar guru Jeff Anderson’s advice and display some interesting compound sentences from authentic grade-appropriate texts and allow students to notice their structural patterns.
  • An innovative teacher might next present a fabulous Prezi with key terms (e.g., independent clause, coordinating conjunction, maybe even conjunctive adverb).
  • A fearless teacher might follow up with the FANBOYS mnemonic device and a rendition of an “original” song about compound sentences set to the tune of “Uptown Funk.”
  • A diligent teacher might then assign a worksheet that provides students with multiple modes for practicing compound sentences.
  • A dedicated teacher might finally send students on their way to write 5 original compound sentences for homework.
  • A thorough teacher, the following day, might assess students’ abilities to independently analyze, evaluate, and compose compound sentences.

And everyone appears to have mastered the compound sentence! Then, that same teacher grades students’ essays the next week and realizes that an overwhelming majority of those little masters are not successful in applying the skill in their own writing. The teacher followed the 5E model, used all Four Rs, scaffolded, and gradually released yet is still left bewildered at the students’ inability to recall the skills necessary for synthesizing the concepts they seemed to have mastered just days before.

Interleaving provides teachers and students with the tools to maximize long-term recall.

According to advocates of interleaving, the problem is that students exhibited only an illusion of success because each sentence they encountered was either an example or a non-example of a compound sentence. It’s easy to appear knowledgeable when the skill is isolated because massed practice allows the brain to take the easy way out, whereas more challenging interleaved practice forces the brain to work harder, encoding “the learning in a more flexible representation that can be applied more broadly” (Brown 52).

It’s Not Wrong, It Just Feels Wrong!

In addition to being radical, interleaving is counter-intuitive.

Counter-intuitive does not mean wrong; it just means it “feels” wrong. Presenting a radical lesson in which you teach two challenging skills or concepts at the same time will feel very uncomfortable. It will be messy, and students will experience failure. Research reveals it is that exact challenge that enhances understanding and memory. Students will not feel successful immediately, but that’s okay because immediate success is not the long-term goal. The ability to recall and then apply, analyze, and synthesize the concepts and skills in your subject area is the long-term goal, right? Interleaving provides teachers and students with the tools to maximize long-term recall.

The Data Doesn’t Lie

A recent study reported in “Interleaved Practice: A Secret Enhanced Learning Technique” (Jenkins) documents the effectiveness of interleaving among students. Students were divided into two groups, Interleaving and Blocking (isolated repetitive practice), and were provided instruction on finding the volume of four obscure geometric solids. The Interleaving group was taught the four formulas and given an opportunity to practice applying all four, such that in each group of four questions, there was one problem of each type interspersed throughout the total of sixteen practice problems. The Blocking group was provided instruction on one formula and given an opportunity to practice applying that isolated formula to four practice problems. Then, they were provided instruction on a second formula and given an opportunity to practice applying the second isolated formula to four practice problems, and so forth. Both groups repeated this process again a week later. The results were surprising and impressive. In practice, the Interleaving group had 60% accuracy compared to 89% accuracy in the Blocking group. But when students were given an assessment the following week, two weeks after initial instruction,

the Interleaving group performed with 63% accuracy,

while the Blocking group performed with only 20% accuracy!

When students are always “successful,” they limit their understanding of the concept to the isolated practice and cannot develop the broader understanding needed to apply the skill in other situations. When they are required to discriminate between two or more skills, to assess the context and determine which skill must be used to solve the problem, they demonstrate significant improvement in recalling and applying the steps and procedures needed to demonstrate mastery of the concept. Pediatric neurologist Douglas Larsen explains, “Making the brain work is actually what seems to make a difference—bringing in more complex networks, then using those circuits . . . makes them more robust” (Brown 66).

And, it appears as if the “interleaving effect is long-term” (Pan). According to this article posted in Scientific American, the long-term effect of interleaved practice continues to widen the gap when compared to massed practice. In other words, students who have employed the interleaving strategy in the learning process continue to retain the skills and concepts over long periods of time, while their classmates who participated in blocked practice of isolated skills continue to forget more and more of what they learned. Now that you think about it, it doesn’t seem so counter-intuitive, does it?

Pioneering Pathways

Unfortunately, neither our students nor we are always the best judges of our own cognitive growth. “Our judgments of what learning strategies work best for us are often mistaken, colored by illusions of mastery” (Brown 81). Employing the strategies of interleaving is pioneering work. Because interleaving will seem difficult, students will likely long for the old way of learning. Fortunately, incorporating the interleaving technique requires only minimal changes in lesson planning and instruction, leaving teachers more time and energy to deal with the possible fears of students who might balk at their new challenge.

The savvy teacher, armed with the interleaving strategy, will:

  • Follow the same lesson plan, but teach compound and complex sentences together.
  • Include opportunities for students to analyze the similarities and, especially, the differences between compound and complex sentences.
  • Guide students to decipher between independent and dependent clauses.
  • Model how to determine if and when commas are needed between independent and dependent clauses of both sentence structures.
  • Have students break compound and complex sentence parts into chunks and rearrange them into meaningful sentences of another structure.
  • Ask students to find and classify sentences of both types in their independent reading.
  • Have students revise previous essays by correcting compound and complex sentences they had attempted before learning how to correctly punctuate them and by combining ideas into compound and complex sentences.
  • Then, allow students to write new essays including both compound and complex sentences.

The beauty of interleaving is that learning lasts beyond the lesson. The tools needed to implement interleaving strategies are already in your possession. Yes, it’s radical! Yes, it’s counter-intuitive! Yes, it’s pioneering! But rethinking and restructuring your current lessons will produce powerful results.

Sources and Further Reading

“Brain Science for Beginners” by Carey Benedict in Independent School. 75, no. 1, Fall 2015 (pp. 88–91)

Interleaved Practice: A Secret Enhanced Learning Technique” by Jake Jenkins on j2jenkins.com

The Interleaving Effect: Mixing It Up Improves Learning” by Steven C. Pan

Make It Stick: The Science of Successful Learning by Peter C. Brown, et al. (pp. 46–101)