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What is the evidence around spaced repetition


May 16, 2020




If you’ve asked yourself: “Does spaced repetition (aka distributed practice) really work or is it just a lot of hype?”, welcome. This article will give you a short, highly interesting timeline of the evidence which supports this learning tool.

It all began in 1939

Herbert J. Spitzer investigated what effect the spacing of material and tests had on recall and retention. Although his results showed promise, they were not really dealt with by others for more than a generation.

Jumping to 1989: Overwhelming evidence that spaced repetition works

Frank N. Dempster published a review of the scholarly literature in the Educational Psychology Review. His conclusion was the weight of evidence showed that spaced repetition is a “highly effective means of promoting learning [over a] variety of settings and across many different types of materials and procedures.” 

1991: Spaced repetition is effective with learners of all ages

A research team at Villanova University, USA ran a two-part, spaced learning experiment.

Part I was on young children (preschoolers, first graders, and third graders). They found that recall increased as the “spacing between repetitions increased”. However, the effect did not relate to age. In other words, age was not a factor, just the spacing between the repetitions.

In Part II of their study, this team conducted a spaced learning experiment using college students. The results were the same.

Their conclusion? “Spaced-repetition effects in recognition are produced by fundamental memory mechanisms that are operational at a very early age and which undergo little change with development.” In plainer English, spaced repetition (or distributed practice) increases recall for anyone at any age.

Moving on to 2016: Distributed practice can save your organization money

According to researcher Sean Kang (Dartmouth University, USA), organizations should capitalize on spaced repetition. 

Kang stated that spaced practice “can be a cost-effective approach.” This is due to the fact that greater retention of material is achieved in the same amount of time. As a result, learners spend less time relearning forgotten material, “leaving more time for other productive learning activities.” 

Overall, distributed practice “enhances the efficacy (effectiveness) and efficiency of learning.”

2017: Effects of spaced repetition age and goal dependent

While distributed practice works for everyone, the results depend on how old the person is and which task they are being taught.

Christopher D. Smith and Damian Scarf (University of Otago, New Zealand) found that for adults, spaced repetition is more effective for teaching skills rather than language. Having said that, this educational technique improves the generalization of learning for all ages. 

Spaced Repetition and Brain Boost

2019: Findings about why spaced repetition works

A team of researchers at Beijing Normal University in China used scalp EEG data to get a picture of the biological basis for the effectiveness of spaced repetition.

The team analyzed the scalp EEG data using spatiotemporal pattern similarity (STPS). Spatiotemporal data analysis looks at information in a particular location (spatio) over a defined period of time (temporal). Using powerful computing processors, large quantities of data can be analyzed in this way to reveal patterns.

The research data showed that “greater item-specific STPS in the right frontal electrodes at 543–727 ms after stimulus onset was associated with better memory performance. More importantly, this STPS was larger under the spaced-learning condition than the massed-learning condition. “ 

In plainer English, during learning, electrical activity happens in the brain. This study found significant activity in the right frontal part of the brain, 543–727 milliseconds after the learning period began. This activity caused better retention of material, and spaced repetition increased the intensity of this activity. 

2020: Data showing how effective spaced repetition can be

British researchers at the University of Leicester wanted to investigate the quantitative effect of distributed practice.

They constructed a custom-built web app. The app could personalize a repetition timetable of study material about physics for each learner. Students could request a spaced repetition timetable, a massed repetition timetable, or not use the app at all.

Here are the results:

  • Learners who chose space repetition had an adjusted mean exam score of 70%.
  • Those who preferred massed usage had an adjusted mean exam score of 64%.
  • Students who did not use the app at all had an adjusted mean exam score of 61%.

The study showed that learners who studied via spaced repetition has the best test results.


Spaced repetition (or distributed practice) is a time-tested educational tool, supported by over 80 years of research data.

Since it increases learner retention over the same amount of study time as massed practice, distributed practice is a budget-friendly option.

It works for learners of all ages. For adults, it is better suited to skills training than language learning.

As researchers investigate this tool further, they find that it causes neurological (brain) activity which enhances learning.

EdApp has taken spaced repetition to the next level with their feature: Brain Boost spaced repetition app. Based on the principles of spaced repetition, Brain Boost spaced repetition app relies on an adaptive, dynamic algorithm that automatically creates interactive lessons based upon core, previously-learned content in any given EdApp lesson.

Get started enjoying the benefits of spaced learning for your organization training here.