On the Potential Limitations of Spacing and Retrieval Practice in the Classroom (and the Need for More Applied Research)

On the Potential Limitations of Spacing and Retrieval Practice in the Classroom (and the Need for More Applied Research)

By Carolina Kuepper-Tetzel

We have been writing a lot about the top two learning strategies that cognitive psychology has brought out: Spacing and retrieval practice. Both learning strategies have accumulated a vast amount of scientific evidence, making us confident to recommend these strategies to teachers and students. However, it is important to keep in mind that our confidence in these strategies stems mostly from many basic laboratory, some applied laboratory, and a few applied classroom studies (see the lab to classroom model below).

Thus, spaced practice and retrieval practice have been predominantly studied in the laboratory using a highly controlled learning setting and simple material (basic laboratory) or educationally relevant materials (applied laboratory). The good news is that both strategies have been demonstrated in the classroom using relevant to-be-learned material as well (1) (2) (3). However, we definitely need more applied classroom research to make a stronger case and to reveal possible limitations. One recent study by Goossens, Camp, Verkoeijen, Tabbers, Bouwmeester, and Zwaan (4) has looked into the effect of spaced practice and retrieval practice for vocabulary learning in primary school children. Their research approach can be categorized into the “applied classroom” category because they used authentic material that pupils were being taught in class and the study was fully integrated into the classroom curriculum. They implemented the retrieval practice and spaced practice interventions in school grades 2, 3, 4, and 6.

Description of spacing and retrieval practice interventions & findings

The entire project ran over a period of 15 weeks. Goossens et al. (4) used two spaced practice conditions: in one condition initial learning of 40 new vocabulary and repetition exercises took place within a week (short spacing condition); in the other condition initial learning of the vocabulary and repetition exercises were spread out over a period of two weeks (long spacing condition). The effects of retrieval practice was examined by having pupils either restudy the vocabulary definitions or retrieve the definitions from memory during the repetition exercises. Performance on the studied vocabulary was assessed 1 to 3 days later using cued recall (i.e., foreign word was given and pupils needed to provide a description of the word) as well as 1 week, 2 weeks or 11 weeks later using multiple choice (i.e., foreign word was given and pupils had to pick the correct description).

Image from Pixabay

Image from Pixabay

The questions Goossens et al. wanted to answer were:

a)     Is there a benefit of long spacing between repetitions compared to short spacing for long-term retention of vocabulary in primary school children?

b)     Is there a benefit of retrieving the word definitions from memory compared to simply restudying them for long-term retention of vocabulary in primary school children?

Based on their findings, the short answer to both questions is: No! In none of their results Goossens et al. find a benefit of the longer spaced condition over the shorter spaced condition. In cases they detected a significant difference, it was actually in the opposite direction; with the short spaced condition outperforming the long spaced condition. Furthermore, they did not find a significant advantage of retrieval practice over restudying. In fact, again, in cases of significant effects, they found that restudying actually trumped retrieval practice. Thus, both main findings from their study seem to be in violation with previous findings and our general recommendations. Can we resolve this dissonance? Let’s take a closer look at the possible factors that may have contributed to the abovementioned findings and see what we can learn from it for the future.

Image from Pixabay

Image from Pixabay

Explanations for the unexpected findings

a) The length of the spacing interval. In their study, Goossens et al. compared different lengths of spacing, i.e., a short spacing and longer one. Previous research has shown that there seems to be an interaction between length of spacing and the length of the interval between the last study session and the final test, i.e. the test interval (5). Thus, for a given test interval, there appears to be an optimal spacing between two learning sessions. For example, for vocabulary learning the optimal spacing for a final test taking place in a week is 1 day (5). In light of these previous findings, it is possible that the short spacing conditions were more adequate for most of the test intervals used (1 day to 2 weeks). What about the long test interval of 11 weeks? Here one would expect long spacing to outperform short spacing. However, one needs to consider that the two spacing conditions used are not extremely different from each other – distributing of studying within one week versus two weeks. It may well be that if one increased the spacing further to create a more extended learning schedule, one would start finding differences in the long term on memory performance.

b) No real restudy only versus retrieval only condition. In order to be as authentic as possible, the authors decided not to have a pure restudy only condition and a retrieval only condition. In all conditions, pupils engaged in exercises that required them to retrieve information from memory at some point during studying. Thus, in contrast to most laboratory studies, the difference between the retrieval practice condition and the restudy condition was much more subtle here. Plus, all pupils engaged in a range of different types of exercises to learn the new vocabulary. This variability in learning may have contributed positively to the overall performance in all conditions – thereby, diluting the effects of restudy versus retrieval.

c) Retrieval exercises too challenging for young pupils. For the younger pupils (grades 2 and 3), the restudy strategy actually outperformed retrieval practice. This is a finding worth looking further into: Could it be that retrieval practice is more beneficial for older kids? Inspecting the memory performance on the retrieval practice exercises in grade 2 children tells us that their performance is lower than that of older children in higher grades. This resonates well with another applied classroom study (3) that clearly showed that younger kids may need more scaffolding during retrieval practice exercises for it to be effective. Goossens et al. mention that children may have focused more on the restudy exercises compared to the retrieval exercises because retrieving the description of new vocabulary from memory may have been too challenging. They report that often blank retrieval sheets were returned. Again, additional scaffolding of the retrieval process could have increased the success of this strategy tremendously.

Image from Pixabay

Image from Pixabay

Recommendations and future direction

Taken together, Goossens et al.’s study provides us with important insights into the factors that we need to further investigate in order to increase the success of spaced practice and retrieval practice in the classroom. It shows that applied classroom studies that evaluate those strategies are invaluable – and we desperately need more. Furthermore, from a research point of view, unexpected, null-effects can tell us a lot about additional variables and factors to consider. Thus, it is crucial for researchers to have an outlet to report these findings as everyone can learn from them. Particularly, if we have the aspiration to provide teachers and students with successful strategies for their classroom instruction, it is important to know what works and what does not work and why.


(1)  Goossens, N. A. M. C., Camp, G., Verkoeijen, P. P. J. L., Tabbers, H. K., & Zwaan, R. A. (2012). Spreading the words: A spacing effect in vocabulary learning. Journal of Cognitive Psychology, 24, 965-971.

(2)  Küpper-Tetzel, C. E., Erdfelder, E., & Dickhäuser, O. (2014). The lag effect in secondary school classrooms: Enhancing students’ memory for vocabulary. Instructional Science, 42, 373-388.

(3)  Karpicke, J. D., Blunt, J. R., Smith, M. A., & Karpicke S. S. (2014). Retrieval-based learning: The need for guided retrieval in elementary school children. Journal of Applied Research in Memory and Cognition, 3, 198-206.

(4)  Goossens, N. A. M. C., Camp, G., Verkoeijen, P. P. J. L., 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 Psychology, 30, 700-712.

(5)  Cepeda, N. J., Vul, E., Rohrer, D., Wixted, J. T., & Pashler, H. (2008). Spacing effects in learning: A temporal ridgeline of optimal retention. Psychological Science, 19, 1095-1102.