Spaced Practice and Working Memory
By: Megan Sumeracki
cover image by Gerd Altmann from Pixabay
Note: this blog post is a tad longer than usual. I’m hoping the headers will help you navigate to the sections that will be most useful to you: Spaced Practice, Working Memory and Resource Depletion, and Chen et al Experiments (1).
Spaced Practice
Even among the top effective, evidence-based study strategies that we write about, spaced practice is one of the best. Spaced practice is all about when you engage in practice. It is better to spread practice out over time, rather than massing (cramming). This is true whether you are reviewing course material (e.g., repeated reading), or better yet practicing retrieval (i.e., bringing information to mind, like when you take a practice test).
One reason spaced practice is among the very top learning strategies is that it is efficient. Spaced practice does not really involve more time than cramming. (Technically, spaced practice involves a bit of advanced planning, and marking time in one’s calendar takes a bit of time, but this is minimal. You also then don’t have to spend time worrying about procrastination and can just relax when not studying, so there is a tradeoff here.)
For example, imagine you are a student. It is the Fall semester, and you have a final exam coming up in 4 weeks. (Given the timing of this blog post, this scenario might be closer to reality than an imagination activity!) This student could wait until the day or two before the exam and then cram. They might spend 12 hours in the library studying those two days before – 6 hours each day, or even worse, 12 hours the day and late into the night before. Or, they could start studying now, studying for say, an hour three days per week, or 30 minutes each week day and one weekend day (six days per week) until the exam. In both cases, 12 total hours are spent studying. However, when the time is spaced out, the student learns more, and what they learn is more durable in the long run. Spacing means our fictitious student will likely do better on their final exam in 4 weeks. And, possibly more importantly, in the Spring when they are in the next class, building upon the knowledge they were supposed to learn this Fall, the student will be in much better shape. Doing well on an exam is only part of what students ought to want. Long-term retention, and the ability to use the information in the future, is extremely important. Spaced practice will help with this.
Spaced practice is awesome for other reasons, too. It works well for learning tons of different subject matter and skills. It is also relatively easy to use. You do, however, have to plan ahead in order to use spaced practice. If you do not think about your final exam until the night before, the opportunity to really leverage spaced practice is largely gone. (Not completely gone, as a person can space on a shorter time-scale, but this is not really the practical ideal for true long-term learning, and so we’ll leave this discussion for a different blog post.)
Image by Gerd Altmann from Pixabay
If you need another reason to love spaced practice, Ouhao Chen and colleagues (1) provide yet another one. They conducted two experiments to investigate the relationship between spaced practice and working memory depletion. First, I’ll provide a primer on working memory and resource depletion, and then I’ll describe the experiments and results.
Working Memory and Resource Depletion
Working memory is the cognitive system that we use to hold information in our minds while we are consciously using it. For example, as you are reading this blog post, you are holding onto the words as you are reading in order to make sense of them. When you solve algebra problems, you hold onto the components of the problem and actively update the values as you complete various operations.
There are a few features of our working memory system that are important here. First, working memory has limited cognitive resources; you can only hold on to, or “work with”, so much information at once. You can, however, retrieve information from long-term memory into your working memory to use, and long-term memory has no known limit on its capacity. So, once you learn something well, you can retrieve it and use it without really taking up too many of your working memory resources.
Second, complex tasks that have a lot of elemental interactivity, or elements that need to be processed simultaneously, place a greater demand on our working memory. Chen and colleagues (1) provide a nice pair of examples of this in their paper. Learning to solve complex mathematical equations has high elemental interactivity. All the symbols within the problem need to be processed together to understand the problem as a whole, and if you are still learning how these symbols operate, then the task has a higher working memory load. Learning new vocabulary tends to have a lower working memory load. Even though the vocabulary terms are all new and the task may be difficult, they can be processed one at a time, and so the demand on working memory resources is lower.
Chen et al. Experiments
We have limited cognitive resources, and if a task requires that we use a lot of those resources, then resource depletion can occur. What does this have to do with massing or spacing practice? With massed practice (cramming), engagement with the material is more continuous than when we space practice over time. With continuous cramming, working memory resources may end up depleting, which could result in less learning as we push through the cramming session. Chen and colleagues (1) tested this hypothesis with primary school children in their authentic classrooms.
Experiment 1
In their first experiment, ten-year-old primary school students (Year 4) in China learned how to add two positive fractions with different denominators (a new area for these students). They participated as part of their classes, so randomization was not possible. One class participated in the massed condition and the other in the spaced condition. (A quasi-experimental design; this is not as strong a design as a true randomized experiment. Experiment 2 addressed this problem.)
During the learning phase, students in the massed condition practiced solving all the problems in one sitting during class. Immediately after the learning phase, they took a working memory test and then a post-test to measure learning of the math operations. Students in the spaced condition practiced the same problems as those in the massed condition, but they were spread out across three learning days. Then, on a fourth day, the students in the spaced condition completed the same working memory test and the same post-test to measure learning.
The students in the spaced condition had higher performance on the working memory test and the post-test compared to those in the massed condition. The results showed a spacing effect (spacing led to greater learning than massing) and provided support for their hypothesis that massed practice leads to working memory depletion.
Experiment 2
In the second experiment, primary school students (Year 5) learned two discrete areas of algebra. The students learned problems in one area during week 1, and the other during week 2. This was done so that the researchers could counterbalance the learning materials and experimental conditions in a within-subjects design, resulting in more confidence that any differences between conditions is due to the manipulated variable (see this post on research methods). The overall procedure was largely the same as in Experiment 1, but one group of students learned using massed practice during week 1 and spaced practice during week 2, while the other group learned using spaced practice during week 1 and massed practice during week 2.
The results from Experiment 2 supported the results from Experiment 1. Working memory performance was higher for students in the spaced condition than students in the massed condition, indicating that massed practice led to more working memory depletion. Students in the spaced condition also showed greater performance on the post-test than students in the massed condition. The students in this experiment were also asked how difficult they thought the working memory test was. When students were in the massed condition during week 1 and the spaced condition during week 2, the working memory test felt a lot easier during the second week (after spaced practice). When students were in the spaced condition during week 1 and the massed condition during week 2, the working memory test felt a lot harder during the second week (after massed practice).
Summary
Overall, these experiments show that spaced practice leads to greater learning than massed practice in a real classroom setting with primary school children, and show that working memory resources are more depleted after massed practice. Avoiding working memory depletion could be one reason why spaced practice is beneficial! When sitting down to engage in a spaced practice session, working memory resources are more likely to be fresh and ready to go. These experiments also provide objective empirical evidence for what many of us have probably experienced: cramming for long periods of time can feel really draining.
To read other blogs that cover spaced practice, check out this constantly updating list of blog posts tagged “spacing”.
References:
(1) Chen, O., Castro-Alonso, J. C., Paas, F., & Sweller, J. (2018). Extending cognitive load theory to incorporate working memory resource depletion: Evidence from the spacing effect. Educational Psychology Review, 30, 483-501. https://doi.org/10.1007/s10648-017-9426-2
