Interleaving: How Mixed Practice Can Boost Learning

Interleaving

 

Interleaving is a learning technique that involves mixing together different topics or forms of practice, in order to facilitate learning. For example, if a student uses interleaving while going over preparation questions for an exam, they might continuously switch between different types of questions that deal with different parts of the material.

Interleaving, which is sometimes referred to as mixed practice or varied practice, is contrasted with blocked practice (sometimes referred to as specific practice), which involves focusing on only a single topic or form of practice at a time.

Interleaving has been shown to facilitate people’s learning in a variety of domains, both when it comes to traditional subjects within academic settings, such as history and math, as well as when it comes to other fields, such as music and sports. Accordingly, the term interleaving effect is used to refer to the psychological phenomenon where people learn better when they use interleaving, compared to when they use blocked practice.

Because interleaving can be such a beneficial technique, it’s worthwhile to learn about it. As such, in the following article you will learn more about interleaving, see the various benefits that it offers, and understand why it works. Then, you will learn how to use interleaving as effectively as possible, whether you want to implement it in your own learning or use it while teaching others.

 

Examples of interleaving

A simple example of interleaving appears in the case of language learning, where someone who is learning new vocabulary words in a foreign language can mix together words pertaining to different topics instead of learning only words from a single topic at a time. For instance, if someone needs to learn about topics such as animals, foods, and clothes for a class, then instead of learning all the words from one topic before moving on to words from the next one, they can mix words from the different topics as they study.

In addition, there are many other ways in which interleaving can be used in educational contexts. For instance:

  • In the case of history, you can mix up the history of different countries. For example, instead of simply learning about the full history of each country at a time, you can interleave different parts of history from each country, based on a common theme, such as their actions during a specific time period.
  • In the case of statistics, you can mix up the types of calculations that are needed for each type of practice exercise. For example, instead of working on only one specific type of question at a time, you can interleave different types of questions, in a way that makes it necessary to be able to actively figure out which method should be used to solve each exercise.

Furthermore, interleaving can also be beneficial in a wide variety of other contexts.

For example, interleaving is beneficial when it comes to musical education, where it can help people learn how to play new musical pieces. One study on the topic, which found a beneficial effect of interleaving, describes its interleaving scheme as follows:

“Ten clarinetists were given one concerto exposition and one technical excerpt to practice in a blocked schedule (12 min per piece) and a second concerto exposition and technical excerpt to practice in an interleaved schedule (3 min per piece, alternating until a total of 12 min of practice were completed on each piece).”

— From “Optimizing music learning: Exploring how blocked and interleaved practice schedules affect advanced performance” (Carter & Grahn, 2016)

Another example of interleaving appears in the case of sports such as basketball and badminton, where it can be used to facilitate the acquisition of important motor skills. For instance, interleaving can help an athlete learn how to throw a ball more effectively, by encouraging them to practice throws from different distances and from different directions in the same session, as opposed to throwing the ball from the same way each time.

Overall, examples of interleaving appear in a variety of domains. Though this technique is most commonly associated with learning and teaching in educational classroom-based settings, where its use by students is generally prompted by teachers, interleaving can also be applied in a wide range of other settings, including in self-driven learning, and in the learning of various non-academic skills.

 

The benefits of interleaving

Research shows that interleaving offers various benefits, such as improved retention of new information, faster acquisition of new skills, and improved mastery of existing abilities. For example:

  • Interleaving two tasks can improve people’s performance on both tasks more than practicing each of the tasks separately, even when they spend less time overall on each task.
  • Interleaving examples from different categories can improve people’s technical skills more than practicing using the same category each time.
  • Interleaving different concepts can help people avoid the confusion that often arises from learning similar concepts at the same time.

In addition, interleaving has been found to have other benefits to learning, such as improved ability to focus and to identify mistakes, as well as improved goal setting.

Overall, interleaving offers various benefits when it comes to the learning process, both by facilitating learning directly in various ways, and by improving related aspects such as goal setting. These benefits make interleaving a good learning technique to use in various situations, especially since it’s a technique that is often simple to implement, as it does not require any special resources.

 

Why and how interleaving works

The benefits of interleaving are attributed to a number of cognitive mechanisms, as a result of the varied ways in which interleaving can benefit learners and the varied ways and situations in which interleaving can be implemented.

One notable mechanism that interleaving is attributed to is contextual interference. Essentially, mixing material increases interference during the performance of a task, which promotes the use of effective learning strategies by learners. This, in turn, leads to better learning of the material, in terms of factors such as retention of information and in terms of people’s ability to transfer information and skills to other contexts.

Another notable mechanism that interleaving is attributed to is discriminative contrast. Essentially, mixing material helps learners notice the similarities and differences between the different concepts that they’re learning.

In addition, another reason why interleaving is beneficial is that it forces learners to figure out what strategies, techniques, and information they need to use in order to solve problems that they encounter. For example, when it comes to learning math, giving students practice questions which only cover material from the last lesson means that students immediately know which technique or set of techniques they need to use in order to solve those questions, even before they read them. Conversely, giving math students a mixed set of problems, which contains questions relating to various different lessons, ensures that the students have to actively figure out which techniques they need to use in order to solve those questions. This encourages them to analyze the questions in-depth, and develop a better understanding of the techniques that they can use to solve them.

Overall, the benefits of interleaving are attributed to a number of cognitive mechanisms, due to the varied ways in which interleaving can benefit learners and the varied ways and situations in which interleaving can be implemented. These mechanisms include increased contextual interference, which prompts the use of learning strategies, and increased contrast between the concepts that learners are interacting with, which helps them see the similarities and differences between them.

 

Interleaving and spacing

The effects of interleaving are distinct from those of spacing, which is the practice of having a temporal gap between learning sessions. Specifically, even though spacing can facilitate learning, and even though spacing often occurs as a result of interleaving, the effects of spacing alone do not explain all the benefits of interleaving.

Furthermore, the effects of interleaving and spacing can sometimes be additive, meaning that you can improve the learning process by implementing both interleaving and spacing techniques at the same time.

However, this isn’t always the case, and there are situations where temporal spacing can interfere with the effects of interleaving. For example, in situations where interleaving helps learners by providing contrast between elements from different categories, spacing can interrupt the interleaving process, by making it more difficult for learners to compare the elements from the different groups.

Overall, while spacing and interleaving are closely related, these are separate phenomena, which can interact with each other in a way that either facilitates or hinders learning, depending on factors such as the type of material being learned.

Note: a closely related phenomenon, which is said to underlie the interleaving effect in some cases, is the distributed-practice hypothesis, which in this context suggests that it is advantageous to spread mentions of related concepts over a study session, rather than to study them together.

 

How to use interleaving

To use interleaving effectively in teaching and learning, you must decide what material to interleave and how to interleave it. Furthermore, it’s important to keep in mind some important caveats about interleaving, such as that it can be hard for learners to engage in and that it is sometimes better to use an alternative approach.

In the following sub-sections, you will learn more about all these decisions and considerations, so you can use interleaving as effectively as possible.

 

Decide what to interleave

The first step to interleaving is deciding what to interleave. For example, this can involve deciding what type of math questions to mix. When doing this, there are several guidelines that you should keep in mind:

  • Use logical criteria for interleaving. The criteria that you use when deciding how to mix the material should make sense given the reason that you want to use interleaving in the first place. For example, if your goal for using interleaving is to avoid being confused by vocabulary words that are similar to each other, then pick a criterion for interleaving that helps you avoid this issue, such as the way the words are spelled.
  • Avoid interleaving items that are too similar. If the items that you want to interleave are too similar to one another, it can feel more like blocked practice than mixed practice, which means that there won’t be a beneficial interleaving effect. For example, if your goal is to interleave different types of basketball throws, then simply switching between two forms of the same throw that are barely different from one another will likely not allow you to take advantage of the benefits of interleaving.
  • Avoid interleaving items that are too different. If the topics that you want to interleave are too different from one another, then the mixed practice can hinder learning, instead of facilitating it. For example, while interleaving different types of math questions might be beneficial, interleaving math questions with history lessons could end up being confusing and distracting instead.

Note that there is no single right way to engage in interleaving, since the effectiveness of this technique depends on a wide range of factors, such as the type of material involved, the environment in which the material is learned, and the learners’ preferences and abilities.

As such, you should assess the situation when deciding what kind of material to interleave. Furthermore, if possible, you should also evaluate the effectiveness of your chosen interleaving approach, and experiment with different approaches to find the one that works best in your particular circumstances.

 

Decide how to interleave

Once you decide what kind of material to interleave, you need to decide how to interleave. This involves two main considerations:

  • How often to interleave. For example, if you interleave different types of math questions, should each type of math question always be followed by a different type, or should there always be five examples of each type of question in a row.
  • In what pattern to interleave. Most notably, you should first decide whether to interleave material in a random or systematic manner. Then, if you decide to interleave in a systematic manner, you should decide exactly in what order to interleave the material. For example, in the case of vocabulary words, you can decide to simply randomly interleave the words from different categories, or you might decide to systematically interleave them so that words from a certain category are always followed by words from a different category.

For a broad example of this, consider a situation where you decide to interleave three topics that you need to study for your exam, represented by the letters A, B, and C.

The following is an example of a blocked study schedule, where you focus on one topic at a time, and finish studying that topic before moving on to the next one:

AAAABBBBCCCC

If you decide to interleave those topics, you might then decide to mix them so that you only spend a short amount of time on each topic, before moving on to the next one, in a systematic manner. This is represented by the following study schedule:

ABCABCABCABC

Alternatively, you can decide to reduce the degree to which you interleave topics at first, as in the following schedule:

AABBCCABCABC

Similarly, you can decide to reduce the degree to which you interleave topics entirely, as in the following schedule:

AABBCCAABBCC

Finally, you can decide to interleave the topics in a random manner, in which case you might end up with the following schedule:

ACBABBABACCC

Alternatively, you might decide to interleave in a partially random manner, for example by deciding that you won’t work on any single topic more than twice in a row, in which case you might end up with a schedule such as this:

BBCABCACCAAB

As in the case of deciding what kind of material to interleave, there is no single right way to decide how to interleave material, since the effectiveness of this technique depends on a wide range of factors.

As such, when deciding how to interleave, you should assess relevant factors, such as the type of material involved and the learners’ preferences. Furthermore, you should try to evaluate the effectiveness of the interleaving approach that you’ve used, and if possible, experiment with other approaches to find out which work best in your particular circumstances.

 

Remember that interleaving can be hard

Interleaving can often be hard and less intuitive to implement than blocked practice, which is one of the reasons why people often rely on blocked practice even when interleaving can be more beneficial.

Furthermore, interleaving can sometimes hinder performance in the short-term, despite generally leading to better learning outcomes in the long-term. This means that during a study session, you might feel that you had a harder time studying and ended up with worse outcomes by choosing to use interleaving instead of blocked practice, even though in the long term you will end up learning better by using interleaving.

In addition, people often underestimate the effectiveness of interleaving, and assume that it’s less effective than blocked practice even in situations where the opposite is true.

Accordingly, it’s important to remember that interleaving can often be hard and frustrating, especially at first, and that it might feel ineffective even in cases where it’s actually beneficial. This will help you set proper expectations for people’s reaction to interleaving, decide when and how to interleave material, and increase the motivation for sticking with the interleaving, both when it comes to interleaving in your own learning as well as when it comes to interleaving while teaching others.

 

Remember that interleaving isn’t always the best option

Although interleaving can often be beneficial, it’s not always the best option, since in some cases, is no better than blocked practice, and can even be worse. For example, one study found that when it comes to learning how to pronounce foreign vocabulary words, blocked practice benefited learners more than interleaving did, meaning that learners benefited more from practicing the pronunciation of words when those words were grouped together based on similarities in pronunciation, compared to when they were not.

This doesn’t mean that interleaving isn’t beneficial. Rather, it simply means that interleaving isn’t always the best option for you, and that there are scenarios where blocked practice might be preferable. Alternatively, there might be cases where a mix of interleaving and blocked practice leads to the best outcome, and so you shouldn’t assume that you must only use one form of learning or the other.

Overall, the main thing to remember is that although interleaving can be beneficial, it’s not always the best option. As such, you should assess your particular situation to determine whether interleaving is worth using, and evaluate its effectiveness over time, while being willing to accept that it might be better to use blocked practice instead.

 

Summary and conclusions

  • Interleaving is a learning technique that involves mixing together different topics or forms of practice, in order to facilitate learning.
  • Interleaving helps people retain new information, acquire new skills, and improve existing abilities in a wide range of domains, such as math, music, and sports.
  • When deciding what kind of material to interleave, you should use logical criteria given the reason that you want to interleave material in the first place, and make sure that the items that you interleave aren’t too similar or too different.
  • The effectiveness of interleaving varies based on factors such as the type of material involved and the environment in which the material is learned, so you should assess the situation when deciding whether and how to interleave; furthermore, if possible, you should also assess the effectiveness of your interleaving over time, and experiment with different approaches to it.
  • Interleaving can be hard, and people tend to underestimate its effectiveness, which is important to keep in mind so you can effectively set proper expectations for people’s reaction to interleaving, decide when and how to interleave material, and increase the motivation for sticking with the interleaving.