When students are introduced to a concept, the instruction is often paired with several illustrative problems. Exposure to these problems enables them to abstract general principles that define the concept, and to subsequently apply the abstracted principles to new situations (e.g. transfer of learning).
Importantly, the sequence in which the problems of different types of concepts are presented during instruction affects concept learning. For example, in a blocked schedule, learners study several problems representative of a single concept (e.g., math problems with addition) are studied consecutively to extract the key features before moving onto the next concept. In contrast, in an interleaved schedule, problems from different concepts are studied intermixed together (e.g., addition, multiplication, etc.) to learn the differences that exist among them. Each study schedule method contributes to learning differently. Although the majority of the research suggests that interleaved schedules produce greater learning gains than blocked, some research has shown that blocked schedules also have the potential to optimize concept learning.
A study by Sana, Yan, and Kim looked at when and how one schedule may be more or less effective than the other.
In several studies, participants studied 6 problems of 3 different statistical concepts, and then were tested on their ability to correctly classify new problems on a final test. Interleaving problems of different to-be-learned concepts, rather than blocking problems by concept, enhanced classification performance. In other words, this provides evidence that interleaving different concepts is better than studying concepts separately. However, the story does not end here.
When interleaving different concepts, more time between the different concepts leads to lower performance. That is, it is better to study different concepts closely together instead of leaving more time between them. The reason is that studying different concepts together teaches you to better discriminate between the different concepts, which is useful especially when they are similar (but not identical).
However, when studying different concepts in different sessions (a blocking schedule), more time between different study sessions leads to higher performance. That is, when you are studying a single concept at a time, more time between sessions is better. The reason for this is that repeated study sessions become more efficient with a longer delay between them, as you update information that you have started to forget.
Interleaved schedules are effective when problems of different concepts are presented (together or individually) with no disruptions in-between the problems. This seems to be because interleaving facilitates between-concept comparison that is susceptible to disruptions. Blocked schedules are effective when there is some form of temporal spacing introduced in-between problems, as the temporal lag allows for some forgetting and subsequent retrieval of problem features, memory traces for which are then strengthened.
There are several straightforward practical ways in which these findings can be implemented in formal educational settings. Course assignments and end-of-chapter practice problems in textbooks may include problems not just from the current topic, but also from previous units or chapters. Instructors can also lead explicit discussions on the commonalities and differences across concepts. This direct instruction may offer benefits not only in terms of increasing students’ understanding, but also in terms of encouraging students to search out comparison opportunities on their own.
Reference
Sana, F., Yan, V. X., & Kim, J. A. (2016, April 11). Study Sequence Matters for the Inductive Learning of Cognitive Concepts. Journal of Educational Psychology. Advance online publication. http://dx.doi.org/10.1037/edu0000119