Shuffling homework problems helps college students learn introductory physics
“Interleaving” between different problem types improves learning
Concentrating periods of practice on individual topics, which researchers call “blocking,” seems sensible because it allows the learner to focus their cognitive effort on mastering one thing at a time. That characteristic may explain the popularity of blocking of homework assignments by topic in many science, technology, engineering, and mathematics (STEM) courses.
Over the past decade, however, researchers have begun investigating the potential benefits of an alternative approach known as “interleaving.” This approach involves repeatedly switching between different topics as opposed to concentrating on one topic at a time. For instance, an “interleaved” physics assignment might contain practice problems addressing torque, acceleration, and magnetism, all shuffled together.
In an effort to better understand the effects of interleaving, Joshua Samani and I recently compared interleaving versus blocking in two sections of a large undergraduate physics course. During each of two four-week periods, one section completed assignments that were interleaved by topic (i.e., containing a random mix of problems such that each successive problem addressed a different topic), whereas the other section completed assignments that were blocked by topic (i.e., containing three problems per topic, presented in succession). To measure the effectiveness of the two approaches, we administered a surprise problem-solving exam at the end of each period.
The surprise exam results, however, revealed a clear winner: Students that had completed interleaved assignments well outperformed those that had completed blocked assignments (with median improvements of 50% and 125% on the two exams, respectively). Thus, homework problems that are shuffled by topic, as opposed to blocked by topic, can help college students learn introductory physics.
One possibility is that it promotes learning via the spacing effect, which is the finding that practice opportunities that are spread out in time (as opposed to concentrated together) are more helpful for learning. Another possibility is that it causes learners to compare different problem types and learn to tell them apart.
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