Blocking is how skills are traditionally developed. For example, this means mastering ‘A’ before moving on to ‘B’. For example, a teacher using a blocking technique might have students master basic addition facts (‘A’) before introducing the concept of subtraction (‘B’). While a teacher using an interleaving technique might teach addition one day, subtraction the next, and then on the third day, combine both skills.
There is promising research behind interleaving when it is compared with blocking. There have been numerous studies on the benefits of interleaving in sports (badminton, baseball, basketball, see the Scientific American article for more details). In 2003, a study found that medical students were able to produce more accurate electrocardiogram diagnosis when taught with interleaving than those taught with blocking.
Research has also shown that, in order for interleaving to be effective, students must be familiar with the topics first. For example, when learning a new language, students do not tend to benefit from interleaving until they reach a point of proficiency. My best guess is that when the starting level of background knowledge is so low, interleaving gives too many new concepts too fast and, as a result, confuses the learner.
When it comes to learning in schools, studies on interleaving have been promising. A 3-month study done on seventh graders learning about slope and graphing found substantial results. About half of the seventh graders were taught with a blocking technique, while about half were taught with an interleaving technique. At the conclusion of the 3-month training, students were given a pop-quiz. Those taught with an interleaving technique score 25% better than those taught with a blocking technique. The results grow even more profound when students were given another pop-quiz one month later. Those taught with interleaving scored 76% better. In short, one reason that interleaving is more effective than blocking is that it leads to less forgetting over time.
Interleaving involves studying multiple topics in one study session. For example, if the subject is science and you are studying the rock cycle, you should cycle between each type of rock and how they change within one study session.
An example would be to spend 5 minutes going over igneous rocks and how they form. Then spending the next 5 minutes going over metamorphic rocks and how an igneous rock can become metamorphic. Then spend 5 more minutes going over sedimentary rocks and how a metamorphic rock can become one.
- Properties of igneous rocks and how they form
- Properties of metamorphic rocks and how they form from igneous rocks
- Properties of sedimentary rocks and how they form from metamorphic rocks
It is important to make connections between one topic and another. This is why you need to make connections between each type of rock (knowing how they change). Doing this helps make connections and knowledge more permanent. Then, after you have finished one round of studying, go over the topics in a different order.
- Properties of metamorphic rocks and how they can become igneous rocks
- Properties of sedimentary rocks and how they can become metamorphic rocks
- Properties of igneous rocks and how they can become sedimentary rocks
This is the step that will be most difficult to achieve for teachers because many students will feel that they have studied everything, why do it again?
I think that one way we can help students to practice interleaving is in how we design our homework and or study guides. To continue with the rock cycle example.
The first part of the assignment could be matching keywords to their definition. Then the students may look at a series of photos and label the type of rock underneath the picture. After that, students could be asked to draw a rock cycle diagram with key terms included. Finally, students could explain how a sedimentary rock could become a metamorphic and igneous rock.
This style of assignment would have students cycling through each stage of the rock cycle throughout the assignment. Teachers can also structure their lessons in similar ways in order to maximize the effect of interleaving. Finally, interleaving is most effective when combined with other learning strategies such as spaced practice, elaboration, and retrieval practice.