In 1885, Hermann Ebbinghaus introduced the world to the forgetting curve. In an impressive-but-limited study, he attempted to memorize nonsensical words and then recall them at different intervals (immediately, a few hours later, many hours later). He realized that memory does decay – and much faster than one might think! The loss is extraordinary in the first twenty minutes, although the memory continues to leak remarkably for the first hour and then trickle out for the next twenty four hours or so.
Ebbinghaus also theorized that there are excellent strategies to strengthen memory (namely mnemonics and spacing). In fact, his work has been studied for more than a century with solid results – so much so that spacing is now considered one of the most potent learning strategies. Consider this graph of the forgetting curve (with spaced learning). The red curve represents natural decay of learning and each subsequent green curve is a study session that ultimately flattens the curve:
Spacing is the mortal enemy of cramming (in at least four critical dimensions).
- Spacing requires discrete study sessions that have an adequate amount of time in between sessions whereas cramming happens all at once.
- Spacing demands intentional planning while cramming thrives on procrastination and lack of planning.
- Spacing is uncomfortable because it activates retrieval muscles but cramming is comfortable (though it is a victim to the illusion of competence).
- Spacing provides durable knowledge and cramming provides ephemeral knowledge.
This validates our gut feeling; revisiting, reviewing, and re-investigating our knowledge makes it stronger. So much so that many of the modern books on cognitive science praise spacing as one of the strongest tools in a learner’s arsenal:
Small Teaching by James Lang
According to the research we reviewed on spacing and interleaving, five 10-minute practice sessions spaced out throughout the course will work more effectively than a single 50-minute practice session. [Kindle location 2,265]
Understanding How We Learn by Yana Weinstein, et al.
Planning (spacing) Spaced practice is the exact opposite of cramming. When you cram, you study for a long, intense period of time close to an exam. When you space your learning, you take that same amount of study time and spread it out across a much longer period of time. Doing it this way, that same amount of study time will produce more long-lasting learning. For example, five hours spread out over two weeks is better than the same five hours right before the exam. But spacing your learning requires advance planning; you can’t just decide to space out your studying at the last minute. [Kindle location 3,193]
Grasp by Sanjay Sarma and Luke Yoquintot
Thought that they made learning harder. Upon the techniques that ticked both boxes, Robert bestowed the name “desirable difficulties.” Spacing instead of massing certainly made the list. It could neutralize the false sense of security given by recently learned facts; plus, by giving retrieval strength time to subside, it gave learners a chance to shore up storage strength; plus, as an additional bonus, there were still all those benefits at the synapse level that neuroscientists had been talking about since the 1970s. [Kindle location 2,682]
How We Learn by Benedict Carey
Let’s say fifteen days, that’s our window. For convenience, let’s give ourselves nine hours total study time for that exam. The optimal schedule is the following: Three hours on Day 1. Three hours on Day 8. Three hours on Day 14, give or take a day. In each study session, we’re reviewing the same material. On Day 15, according to the spacing effect, we’ll do at least as well on the exam, compared to nine hours of cramming. The payoff is that we will retain that vocabulary for much longer, many months in this example. We’ll do far better on any subsequent tests, like at the beginning of the following semester. [Page 78]
Powerful Teaching by Pooja Agarwal and Patrice Bain
After one week, the cramming condition led to slightly higher exam performance compared to the spacing condition. After four weeks, however, performance in the cramming condition dropped by more than half, while exam performance for the spacing condition decreased only a little bit, from 70% to 64%. In other words, simply completing 10 math problems spaced out over two weeks instead of one week dramatically reduced forgetting. [Kindle location 2,115]
Make it Stick by Peter C. Brown
On the other hand, when you let the memory recede a little, for example by spacing or interleaving the practice, retrieval is harder, your performance is less accomplished, and you feel let down, but your learning is deeper and you will retrieve it more easily in the future. [Page 75]
The good news is that spacing works. Tell your students that flashcards are a great, cheap, and easy way to practice. But there’s a few rules:
- Practice with the flashcards every few days (spacing)
- Shuffle the cards between rounds
- Don’t take cards out of the deck when you get them right – wait until the third or fourth time you get them right before removing them
- And, for an added bonus, keep flashcards from previous chapters in the mix (interleaving)
And remind students that whatever spacing mechanisms they settle on will probably feel uncomfortable. But it will be worth it in the long run.
Photo by Kelly Sikkema on Unsplash
