Why would draining working memory explain the benefit of spacing?
The spacing effect is the finding that learning is usually better when study sessions are spread out over time than when they are crammed together. One way to explain it is to treat working memory as a limited resource that gets used up during effortful learning. On this account, massed practice consumes that resource faster than it can recover, so later study within the same session is less effective. Spacing inserts rest intervals that allow the resource to recover, and the recovered capacity supports better learning on the next round [3][5].
This proposal is an extension of cognitive load theory, which normally focuses on how much information working memory can hold at once. Adding resource depletion means adding a second idea: that working memory also becomes fatigued over time and recovers during rest. The spacing effect is used as a test case for whether that addition is warranted [3]. In practical terms, the theory predicts that study schedules which give working memory time to recover should outperform schedules that do not.
Do experiments actually link depletion to the spacing benefit?
The experimental picture is not clean. One set of experiments examined element interactivity, mental rehearsal, and working memory resource depletion alongside the spacing effect. It found clear evidence of the spacing effect in one experiment, but the depletion measures did not line up neatly with the spacing benefit. Mental rehearsal was proposed as a possible explanation for the spacing effect in that experiment, yet there was no condition that confirmed it [1]. In other words, the spacing effect appeared, but the depletion story did not fully account for it.
The theoretical papers are more confident that depletion is a useful framework, but they present it as a proposal to be tested rather than a settled finding. The 2018 paper explicitly frames the spacing effect as a way to test whether resource depletion should be added to cognitive load theory [3]. The 2022 reply acknowledges other explanations for the spacing effect and discusses how well the depletion explanation matches or fails to match them [5]. That is a debate about fit, not a demonstration that depletion is the cause.
What should a learner take from this?
The practical advice does not depend on the depletion explanation being correct. Spacing study sessions is well supported as a learning strategy, and the depletion account is one attempt to say why it works [3][5]. If the depletion account is right, then rest breaks during study are not just a comfort measure; they may be functionally necessary for working memory to recover. If it is wrong or incomplete, spacing may still help for other reasons, such as giving memory consolidation time or creating more varied retrieval contexts.
For instructional design, the depletion idea suggests that scheduling spaced practice is a way to manage working memory demands over a learning sequence [2]. But the evidence does not yet justify treating depletion as the single lever. The mixed experimental results mean that a learner or teacher should treat spacing as a robust technique and treat the depletion explanation as a promising but unconfirmed mechanism [1][5].
Sources used in this answer
The effect of element interactivity and mental rehearsal on working memory resource depletion and the spacing effect
Experiments found clear evidence of the spacing effect in one experiment, but working memory resource depletion did not cleanly account for it, and mental rehearsal was proposed as a possible explanation without a confirming condition.
Cognitive load theory, spacing effect, and working memory resources depletion: Implications for instructional design
The paper discusses spaced practice within cognitive load theory and suggests the spacing effect can be used to investigate working memory resource depletion in learning.
Extending cognitive load theory to incorporate working memory resource depletion: Evidence from the spacing effect
The paper proposes adding working memory resource depletion to cognitive load theory and uses the spacing effect as a test case for whether that addition is advisable.
Working memory resource depletion effect in academic learning: steps to an integrated approach
The paper examines working memory resource depletion in academic learning but does not address the spacing effect.
Reply to Sana et al.'s (2022) Commentary on Rest-from-Deliberate-Learning as a Mechanism for the Spacing Effect
The reply acknowledges other explanations for the spacing effect and discusses how well the working memory resource depletion explanation matches or does not match them.