Everything you need to know about the spacing effect

There is a huge and teeming literature of learning theory which, let’s be honest, most of us don’t have the time to read. This is probably why a lot of really good stuff sometimes doesn’t get applied. It’s frankly just too big a task to wade through it all – taking care to avoid the snake-oil and fanciful notions with no basis in peer-reviewed science – and come up with something you can put into practice tomorrow morning.

But if there’s one principle in learning theory it would really pay any learning professional to get their head around – a finding that has been proven to work in study after study, and observed paying fruit in real-world situations – it’s the spacing effect. So here’s a no-frills guide to what it is and how it can work for you which doesn’t require a Ph.D. in experimental psychology. It will take you five minutes, tops, to read it; but it could change your whole approach to training. Thank me later.

What is the spacing effect?

It’s based on the Ebbinghaus Forgetting Curve. Our understanding of the spacing effect starts with Hermann Ebbinghaus, who in the late 19th Century carried out research into memory, which is of course the basis of learning. He found that memory decays at an exponential rate. Within minutes, we forget what we’ve learned or been told. After 20 minutes we remember only 58%, after a day 34%, after 31 days 21%.

The good news is that memory decay is regular and predictable. It can be plotted on a curve, giving us a guide to how we can counteract its effects through spaced practice.

Other scientists built on Ebbinghaus’s insights, fleshing out the picture of how memory works to shift stuff from short-term memory into long-term memory, and discovering other effects, like chunking, interleaving, etc. This gives us a sound basis of science on which to build learning design.

Replication crisis

The spacing effect is one of the most robust findings in the literature. Ebbinghaus’s findings have been confirmed by numerous replications of his experiments down the years. This is significant because there is a ‘replication crisis’ in science, with many classic experiments having found not to be replicable. This replication crisis is especially acute in the field of psychology – leading researchers to proclaim the spacing effect one of the most robust findings in the psychological literature.

We know it works because we use it every day in our own lives.  It may have an impeccable grounding in empirical research, but the spacing effect is far from being an obscure scientific principle known only to learning theory ‘geeks’. In fact, ordinary people use it every day when they are revising for exams, cramming for a driving test, or learning to play a musical instrument. We instinctively know this is the way to learn and fall back on it when we need to acquire a critical skill. Swedish psychologist K. Anders Ericsson studied the crucial part that spaced practice has played for people who achieve expert performance in medicine, music, chess, and sport—findings that were popularized by best-selling journalist and author Malcolm Gladwell in his 2008 book Outliers: The Story of Success.

Despite all this, the spacing effect isn’t much used in digital learning or formal education. No doubt this is in part due to the practical difficulties associated with implementing spaced practice in pre-internet days: once the learner left the classroom or the training suite, it was not easy to follow them. Also, cohort-based implementations of spaced practice are always liable to be a rather blunt instrument: it is so dependent on the individual setting a rhythm of repetition for themselves. As a result, spaced practice has tended to be used in a very ad hoc way, historically. Teachers and trainers might recommend it to their learners, but whether the learner actually did it or not would be very much a matter of personal choice.

Practical barriers to adoption

Digital technology has dissolved many practical barriers to adoption. It is eminently practicable nowadays to ‘follow’ learners online after they have finished a training event, and most importantly to personalize learning programs. If we ask why digital technology has not led to wider use of spaced practice in formal programs, it is perhaps because, in the first decade and a half during which learning technologies was a viable industry, vendors and their clients have largely had a focus on efficiency of delivery as opposed to effectiveness. Together with a lack of evaluation and a laser-like focus on content, this has meant that for many years, learning systems largely confined their role to the administration of learning, and principles of learning design have been applied largely at the level of courses rather than systems, precluding any use of spaced practice. Learning has been conceived as an event, rather than the process it truly is. However, this has changed in recent years, with the introduction of more learner-focused systems that allow learners to pursue individual learning paths over time. Modern systems now have scheduling tools and allow mixed media, making spaced practice relatively easy to implement.

There has never been a better time to use spaced practice for learning programs than now. As we have seen, we have dependable science to guide us in the adoption of spaced practice, and learning technology has now matured to a point where it can handle spaced practice programs. We have the science, we have the tech. And a third factor, perhaps the most important, is user acceptance. If we were going to introduce something to our learner populations that was entirely new and unfamiliar in their experience, we might have a hard row to hoe. However, the enormous success in the consumer market of learning apps such as Duolingo, which teaches the basics of foreign languages via a bright, fun, gamified interface, provides a proof-of-concept. Duolingo uses spaced practice, and it has proved extremely popular, gaining 500 million registered users.

Final thoughts

So there you have it: all you need to know about spaced practice in five minutes. If you want to take your knowledge further, however, and want to use the spacing effect in your own learning programs, we have created some more detailed resources to guide you. Read the other blogs in this series here or download our latest whitepaper, ‘The Spacing Effect: Harnessing the Power of Spaced Practice for Learning That Sticks‘.