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  • Writer's pictureYue Qiu

The Mystery of the Spacing Effect in Learning

The spacing effect describes the phenomenon whereby distributed learning can enhance memory. This article talks explores this effect and about the neural mechanism behind it.

Hi! Today we are going to talk about the spacing effect. Before the introduction, I want to ask a question: when you are learning, do you prefer to dig into one subject for several hours, or study one or two hours per day? We can call the latter format distributed learning, and it is linked to the spacing effect. The spacing effect describes the phenomenon whereby distributed learning can enhance memory. The spacing effect was first proposed by Ebbinghaus. Since then, it has been widely encountered in psychological studies. One of the most famous studies was psychologist Bahrick’s research about the spacing effect in foreign language vocabulary learning, which was conducted by the whole Bahrick family and lasted for 9 years. Bahrick, his wife and their two daughters both participated in this research and chose a foreign language to learn. 300 foreign word pairs were divided into 13 or 26 sessions, and relearned after 14, 28, or 56 days. The ability to recall these words was tested after 1, 2, 3, or 5 years after learning. The results showed that the 56 days interval in learning resulted in the most effective retention, showing the benefits of spacing learning for long-term memory.

But why? What is the neural mechanism of the spacing effect? How does it work? Many researchers have the same questions. Bjork and Bjotk propose a theory about the mechanism behind the spacing effect which points out that the weaker the retrieval strength in the repetition process, the stronger the storage strength for long-term memory. In 2014, a group conducted research to test this hypothesis via fMRI and EEG. Participants were divided into two groups to study 180 words and got an unexpected exam after 24 hours. One group carried out bulk learning, while the other experienced spaced learning. The result of EEG data showed that the spaced learning group had weaker retrieval strength. Additionally, brain areas linked to subsequent memory showed greater fMRI responses during the learning process, which means that better storage strength resulted from the stronger encoding process due to spaced learning.

Another hypothesis holds that repeated exposure to an item can remind people of previous experiences with the item, thereby promoting the long-term retention. A study was conducted to explore the neural processes behind the interval effect. In this study, 30 participants were asked to learn words; the data from multivariate ERP analysis confirmed the spacing effect occurring behind the centro-parietal scalp.

However, researchers advocate that the mystery of the spacing effect still needs deeper research to identify underlying mechanisms, especially in terms of how different kinds of retrieval produce different effects influencing storage strength. Have you ever experienced the magic spacing effect before? If so, can you understand it better now? If not, do you want to have a try and adjust your learning strategy?



Bahrick, H. P., Bahrick, L. E., Bahrick, A. S., & Bahrick, P. E. (1993). Maintenance of Foreign Language Vocabulary and the Spacing Effect. Psychological Science (0956-7976), 4(5), 316–321. Bjork, R., & Bjotk, E. (1992). A new theory of disuse and an old theory of stimulus fluctuation. Essays in Honor of William K. Estes, Vol. 1991: From Learning Theory to Connectionist Theory, 1935–1967. Ebbinghaus (1885), H. (2013). Memory: A Contribution to Experimental Psychology. Annals of Neurosciences, 20(4),155–156. Kim, A. S. N., Wiseheart, M., Wong-Kee-You, A. M. B., Le, B. T., Moreno, S., & Rosenbaum, R. S. (2020). Specifying the neural basis of the spacing effect with multivariate ERP. Neuropsychologia,146,107550. Vlach, H. A., Sandhofer, C. M., & Kornell, N. (2008). The spacing effect in children’s memory and category induction. Cognition,109(1), 163–167. Zhao, X., Wang, C., Liu, Q., Xiao, X., Jiang, T., Chen, C., & Xue, G. (2015). Neural mechanisms of the spacing effect in episodic memory: A parallel EEG and fMRI study. Cortex, 69, 76–92.

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