Interleaving: A Classroom Experiment

https://www.learningscientists.org/blog/2021/10/28-1

The researchers (1) were interested in whether interleaving math problems over time would lead to superior learning than blocking them. Importantly, in this experiment, there were all different types of math problems.

During this time, the students received their normal lessons and assignments. There were four different types of problems that were a part of the experiment, and the students’ assignments were constructed so that across the nine weeks they saw 12 different problems of each of the four types. All students learned two types of problems interleaved throughout the assignments, and they learned the other two types of problems blocked in the assignments.

When a type of problem was learned through blocking, all 12 practice problems for the students to solve appeared in the same assignment. When a type of problem was learned through interleaving, the first four practice problems for the students to solve appeared in one assignment, and the remaining eight practice problems were distributed across the remaining assignments. In other words, these last eight problems were all mixed up in later assignments to create interleaving.

Two weeks after the none-week learning phase ended, the students were given a surprise assessment test. The test was a surprise so that students would not cram before the test.

The results are short and sweet! Interleaving practice resulted in test performance that was almost twice as high as blocking practice. Students earned 72% on the problems they interleaved, whereas they earned 38% on the problems they blocked.

References:

(1) Rohrer, D., Dedrick, R. F., & Burgess, K. (2014). The benefit of interleaved mathematics practice is not limited to superficially similar kinds of problems. Psychonomic Bulletin & Review, 21, 1323-1330. https://doi.org/10.3758/s13423-014-0588-3