spaced-repetitionBackground: In education, the fact of the matter is that the traditional classroom lecture isn’t going anywhere.  Many of us realize that this is not the most optimal way to accomplish knowledge acquisition.  Typically, a large amount of information is presented in a 30 minute to 1 hour format – if we’re lucky, maybe 10 – 20% of this information is retained and able to be recalled. Spaced repetition is a learning technique that can be used by learners and deployed by educators in order to improve the efficiency of knowledge retention and recall. In a nutshell, after the initial information is presented, the material is reviewed in smaller chunks that are spaced out at increasing intervals of time. While it’s become clear that spaced repetition helps to improve long-term knowledge retention, it remains to be seen if this can also be used to improve different aspects of medical care, such as improving clinically-relevant skills. But a new study of urology residents looks to answer this question.

What They Did:

  • Multi-institution, RCT of US urology residents separated into 2 cohorts:
    • Cohort 1: 3 cycles of spaced education on prostate-testis histopathology (weeks 1 – 16) and 3 web-based teaching (WBT) modules on bladder-kidney (weeks 14 – 16)
    • Cohort 2: 3 cycles of spaced education on bladder-kidney (weeks 1 – 16) and 3 web-based training (WBT) modules on prostate-testis (week 14 – 16)
    • Each cycle was 4 weeks long and had 20 questions with unique images
    • WBT used identical content and delivery systems, with three 20-question modules



  • Primary: Long-term retention of all 4 topics assessed during weeks 18 – 45
  • Secondary: Long-term learning efficiencies of online educational methodologies, residents’ performance on spaced education versus WBT during weeks 1 to 16, and preference of online learning formats


  • All US urology residents in training years 1 – 4
  • Recruitment through email


  • None


  • 724 urology residents enrolled
    • Spaced Education Completed: 77% of Enrollees
    • WBT Completed: 66% of Enrollees
    • Post assessment Completed: 64% of Enrollees
    • All 3 Assessments Completed: 49% of Enrollees
  • Mean Long Term Score Increase:
    • Spaced Education: 15.2%
    • WBT: 3.4%



  • Questions were pilot-tested by 30 urology chief residents
  • Identical evaluative/educational items used for both spaced education and WBT
  • Randomized design of study
  • Large percentage of urology residents across the United States who enrolled


  • This study focuses on a narrow set of diagnostic skills (i.e. histopathology) that are improved and retained with spaced repetition, but it is unclear if this is the case with surgical skills
  • Only 49% of enrollees completed all three assessments
  • There were differences between baseline scores in spaced repetition cycle 1 versus WBT module 1 which – these were thought due to unanticipated transfer of learning from spaced repetition cycles 1 and 2 (Weeks 1 – 8) to the WBT module 1 (Week 14)


  • Bolus WBT had better short-term retention in scores, but after 3 months these scores fell back to baseline levels
  • With spaced repetition, skills learned in cycle 1 seemed to improve performance on new content presented in cycle 2, which then also improved performance on new content presented in cycle 3
  • 77% of respondents preferred spaced repetition over WBT and 99% of respondents requested to participate in future spaced repetition programs

Author Conclusion: “Online spaced education generates transfer of histopathology diagnostic skills and substantially improves their long-term retention. Additional research is needed to determine how spaced education can optimize learning, transfer, and retention of surgical skills.”

Take Home Point: Spaced repetition increased long-term learning retention 4-fold compared to traditional mass presentation.


  1. Kerfoot BP et al. Online Spaced Education Generates Transfer and Improves Long-Term Retention of Diagnostic Skills: A Randomized Controlled Trial. J AM Coll Surg 2010; 211: 331 – 337. PMID: 20800189

5 thoughts on “▸ Spaced Repetition: Proof of Concept

  1. Jeff Riddell says:

    Solid review. Important article for graduate medical education. Thanks for this post!

  2. One problem with this trial is its simplicity. We are rarely trying to keep on top of just one topic. It is certainly a useful strategy but it is not a panacea.

    1. Salim Rezaie says:

      Hey Matt,
      TY for reading…and agreed…teaching and education are never simple…have to use multiple strategies and tools. One of the many tools we have is spaced repetition…it is obviously not the only one, and it doesn’t work in every environment. But one thing that is proven is that things that take effort to remember, are generally retained for longer periods of time. Appreciate the input.


  3. Jo_VanKerkhoven says:

    Thank you for this, this is really interesting because I do believe it will help!
    But how do you do this spaced repetition?? You have a session about a topic, and how do you repeat it? And what about the next sessions? After a while there is a lot to repeat, isn’t it?

    1. Salim Rezaie says:

      Think of using flashcards…the things you remember better, you repeat less, and the things you have difficulty remembering you repeat more. You can change the order of the cards to individualize what you need more and less help with remembering. Hope the analogy helps.


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