The Failed Spacing Effect 30 Years Later (Part 2)

The Failed Spacing Effect 30 Years Later (Part 2)

By Yana Weinstein

Thirty years ago, Frank N. Dempster wrote an article entitled “A Case Study in the Failure to Apply the Results of Psychological Research” (1).

In Part 1 of this blog, I looked at the first 5 potential reasons described by Dempster in his review. In this follow-up, I look at the remaining 4 reasons. 

Reason #6: "Too Many Studies Using School-Like Activities Have Failed to Show the Spacing Effect"

Here, Dempster cites a number of papers studies that found massed practice to be as good as spaced practice, or in some cases even better. Dempster refers to these situations as "boundary conditions" - i.e., conditions under which spacing may no longer be effective. In particular, he highlights the finding that massed practice outperforms spaced practice on immediate tests (2). Indeed, more recent evidence (3) confirms that massed practice (aka cramming) can be more effective than spaced practice when the test is taken right after the cramming session. However, that type of temporary learning effect is not what we are looking for in education. 

Another boundary condition of the spacing effect that Dempster identifies is the age of the students being tested. He refers to studies with preschool age children (4) that don't show benefits of spacing. However, more recent research suggests that spaced retrieval practice schedules can actually be of considerable benefit even to such young children (5), refuting this concern.

The last possible boundary condition raised by Dempster is the specific lag (i.e., the length of the space in between study or practice sessions) that optimizes spaced practice. Though there's no straightforward answer to the question of optimal lag, considerable work has been undertaken on this issue in the past few decades (6). This research suggests a complex relationship between prior knowledge, retention interval, and speed of acquisition - one that I feel is beyond the scope of what we need to worry about as teachers (but potentially of great interest to learning engineers).

Reason #7: “The Phenomenon Has Not Been Demonstrated Satisfactorily in the Classroom"

Here is one area where progress has definitely been made in the past 30 years: studies have found spaced practice to be more effective than massed practice in classrooms where students learned vocabulary (7), US history facts (8), and reading (9). This is not to say, however, that all classroom studies of spaced practice have found the effect: a recent paper reported no benefit of spaced practice for children in grades 2-6 (10), though one possible explanation for this finding is that the "massed" condition of that experiment was actually spread out across multiple days. Overall, here we finally do see some progress in the literature relative to where we were 30 years ago, and hopefully the next few decades will bring even more large-scale classroom research on the spacing effect.

Reason #8: “Too Little Is Known About Actual Classroom Practice to Justify Widespread Application of the Spacing Effect”

This is an interesting point that I've never really thought about (though it seems so important!). The question is, what do teachers already do in the classroom? How much time is already spent going back and reviewing previous information (i.e., spaced practice)? Anecdotally, from conversations with teachers, such recaps are few and far between due to the volume of the curriculum and lack of time in which to teach it. I do not know of systematic studies designed to address the question of how often teachers engage in spaced practice when not part of an experiment or a intervention, but it could be out there - a topic for a future blog post, perhaps?

Reason #9: “The Phenomenon Is Not Sufficiently Understood”

The final reason addresses competing theories of the spacing effect - the mechanisms behind it. The theory Dempster devotes most space to (no pun intended!) is that of student interest, as he demonstrated in his own data that students found it more interesting to engage in spaced practice than massed practice, and thus paid more attention and learned more; some recent evidence from the mind-wandering literature is in line with the idea that students pay less attention during massed practice (11). But Dempster's 1988 paper pre-dated the publication of the Bjorks' new theory of disuse in 1992 (12) - a theory that can account for the spacing effect through the interplay of storage strength and retrieval strength (see this guest post for an explanation of these two concepts, and the theory). Another possibility is that spacing provides opportunities for more varied learning contexts than does massed practice (13).

Overall, my assessment of the situation is that the spacing effect remains an important phenomenon to study with respect to educational practice. But while demonstrations of the effect in classrooms are increasing and theoretical progress is being made, the literature remains fragmented, with too many disconnected strands hindering the efficiency of scientific progress. 


(1) Dempster, F. N. (1988). The spacing effect: A case study in the failure to apply the results of psychological research. American Psychologist43, 627-634.

(2) Gordon, K. (1925). Class results with spaced and unspaced memorizing. Journal of Experimental Psychology, 8, 337-343.

(3) Rawson, K. A., & Kintsch, W. (2005). Rereading effects depend on time of test. Journal of Educational Psychology97, 70-80.

(4) Toppino, T. C., & DiGeorge, W. (1984). The spacing effect in free recall emerges with development. Memory & Cognition, 12, 118-122.

(5) Fritz, C. O., Morris, P. E., Nolan, D., & Singleton, J. (2007). Expanding retrieval practice: An effective aid to preschool children's learning. The Quarterly Journal of Experimental Psychology60, 991-1004.

(6) Cepeda, N. J., Coburn, N., Rohrer, D., Wixted, J. T., Mozer, M. C., & Pashler, H. (2009). Optimizing distributed practice: Theoretical analysis and practical implications. Experimental Psychology56, 236-246.

(7) Sobel, H. S. , Cepeda, N. J. , Kapler, I. V. (2011). Spacing effects in real-world classroom vocabulary learning. Applied Cognitive Psychology25, 763–767.

(8) Carpenter, S. K. , Pashler, H. , Cepeda, N. J. (2009). Using tests to enhance 8th grade students retention of U.S. history facts. Applied Cognitive Psychology23, 760–771.

(9) Seabrook, R. , Brown, G. D. , Solity, J. E. (2005). Distributed and massed practice: From laboratory to classroom. Applied Cognitive Psychology19, 107–122.

(10) Goossens, N. A., Camp, G., Verkoeijen, P. P., Tabbers, H. K., Bouwmeester, S., & Zwaan, R. A. (2016). Distributed Practice and Retrieval Practice in Primary School Vocabulary Learning: A Multi‐classroom Study. Applied Cognitive Psychology30, 700-712.

(11) Metcalfe, J., & Xu, J. (2016). People mind wander more during massed than spaced inductive learning. Journal of Experimental Psychology: Learning, Memory, and Cognition42, 978-984.

(12) Bjork, R. A., & Bjork, E. L. (1992). A new theory of disuse and an old theory of stimulus fluctuation. From learning processes to cognitive processes: Essays in honor of William K. Estes2, 35-67.

(13) Maddox, G. B. (2016). Understanding the underlying mechanism of the spacing effect in verbal learning: a case for encoding variability and study-phase retrieval. Journal of Cognitive Psychology28, 684-706.