spaced repetition schedule

The Best Spaced Repetition Schedule

Spaced Repetition is one of the most effective forms of learning. It works particularly well with microlearning as information is broken down into small, easily-digestible microlessons that are easy to repeat. Advancements in eLearning mean that spaced repetition efficiency is enhanced by computers’ ability to remember which questions a learner got right. This means that only core topics which a learner has struggled with get repeated. However, if lessons are repeated too frequently or too infrequently, spaced repetition stops working. So what is the best spaced repetition schedule?

What is a spaced repetition schedule?

A spaced repetition schedule dictates how frequently lessons should be re-taken in order to boost retention and embed knowledge. It governs the duration of the increasing gaps used by the spaced repetition learning methodology which counters the Ebbinghaus forgetting curve. Popular schedules include SuperMemo SM-2 and Mnemosyne. Without a sophisticated spaced repetition schedule, recall easily diminishes over time.

Why do you need a spaced repetition schedule?

If you repeat learning at the wrong frequency, long-term recall and embedding are diminished. If you repeat learning too frequently, retention improvements are redundant as the memory simply hasn’t had a chance to decay. If it’s repeated too infrequently then retention and recall lapse and learning needs to be started again.

What does a spaced repetition schedule look like?

Gwern offers great analysis on spaced repetition frequency. Their following graphs are instructive. They illustrate why cramming is ineffective for anything other than short-term retention but that correct spacing is necessary for the brain to best retain information:

forgetting curve spaced repetition schedule
Ebbinghaus’ original forgetting curve.
forgetting-curve-wozniak spaced repetition schedule
Wozniak’s Supermemo take on dealing with the forgetting curve using a spaced repetition schedule.

What is the best spaced repetition schedule?

In 1990, P.A. Wozniak published a Master’s Thesis called “Optimization of Learning” in which he describes an algorithm based called SuperMemo-2 – SM-2 for short. It’s derived from a trial-and error approach that took years to perfect. He says of it:

“During the first year of using the SM-2 algorithm (learning English vocabulary), I memorized 10,255 items. The time required for creating the database and for repetitions amounted to 41 minutes per day. This corresponds to the acquisition rate of 270 items/year/min. The overall retention was… 92%.

“Separating items previously grouped in pages and introducing E-Factors were the two major components of the improved algorithm. Constructed by means of the trial-and-error approach, the SM-2 algorithm proved in practice the correctness of nearly all basic assumptions that led to its conception.”

You can read more about the math behind SM-2, the numbers behind its spaced repetition schedule and e-Factors, here.

In the succeeding years, SM-2 has been the basis of many algorithm tweaks (such as Mnemosyne) and “improvements,” however, few have proved popular often due to increased complexity that hinders measurement. As such the elegant simplicity of SM-2 makes a compelling case to be the de facto spaced repetition schedule of choice.

If you’d like to know more about EdApp’s implementation of spaced repetition – called Brain Boost (which is based upon SM-2) – and how it enhances institutional and corporate training, get in touch at You can also try EdApp’s Mobile LMS for free by signing up here or in the box below.

Spaced Repetition App – 3 things to look for
How to make learning by repetition more effective
How to boost rote memorization with spaced repetition
What is distributed practice and why you must use it

Leave a Reply