The Spacing Effect

Some of you may wonder why there are so many spaces between each letter in the title "Study". Let your brains run free for a moment to explore the many possibilities: does it represent time spent studying, when you could have been out with friends/playing Pokemon Go? Does it represent the gaps of procrastination time you spend on Facebook/Snapchat/Instagram? Or is it just to grab readers' attention?

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Some of you might wonder why there are so many spaces between each letter for the title “Studying.” Let me allow your brains to run freely for a moment to explore the numerous possibilities: Does it represent the time that studying has occupied, when you could have gone out with friends/play some Pokemon Go? Does it represent the gaps of procrastination time that you spend on Facebook/ Snapchat/Instagram? Or is it just to catch readers’ attention?

The answers are: no, no, and to some extent.

Let’s not beat around the bush. The spacings are actually the protagonist in this article, because today, you will be introduced to a technique that you’ll wish you’d learnt about earlier, which will not only greatly improve your memory retention, but could potentially boost your score in exams. Ladies and gentlemen, let us welcome “The Spacing Effect.


As early as 1885, a German psychologist, Hermann Ebbinghaus, had already discovered the power of spaced intervals in learning and memory. In later years, this effect has been repeatedly demonstrated, especially in animal learning tasks. The most notable one was the Morris water escape experiment (Klapdor K et. al), whereby the mice that have received spaced trials performed better in mastering the task than those that have received mass trials, and furthermore, remembered the starting position of the maze for a longer period of time. When this effect was extended to classroom-based study, the results were no less surprising. Whether it was fifth graders learning uncommon English words (Sobel et. al.), or eighth graders retaining their US history content (Cepeda et. al.), or first graders in their mastering of phonics reading skills (Seabrook et. al.), it was demonstrated that those students with spaced out review sessions retain a significantly greater proportion of information.

How to get the optimum effect

You may ask: “Does longer spacing translate to better memory retention?” Some might even cheekily add: “Surely, if our teacher teaches us this material, and I revisit next year, right before my exam, the spacing effect will also work on me?”

Unfortunately, similar to enzymes with their optimal pH and temperature, this spacing effect also has its optimum spacing gap. Cepeda et al. found that shorter spacing gaps (for instance, a gap of 1 day) is beneficial for short-term retention, whereas longer spacing gaps (for instance, a gap of 20 days) is more beneficial for long-term retention.

The science behind the Spacing Effect

As young budding scientists and medics, I am sure that zillions of questions are firing from the frontal lobe of your brains. One of the questions, for instance, might be “Why does the spacing effect increase my memory retention? I want scientific evidence, not just experimental results!”

Our hippocampus mediates several important functions and plays a significant role in our daily activity of learning and remembering. In this brain region, the input “machine,” dentate gyrus, is crucial for these functions. Thousands of neurons are created there per day, but many of them die in a few weeks. It was previously discovered that there is a correlation between the number of new cells remaining in this region and the strength of our memory. Hence, it can be inferred that the spacing effect may have something to do with increasing or retaining the number of cells in the hippocampus. Yet, currently, there still remains a lot of hypotheses as to why it works. By simply looking at the different views that exist — study-phase retrieval theory, deficient processing theory, retrieval effort and strategy shift hypothesis — one can conclude that there is still no definite answer to this question to date.


Finally, let us address the long awaited question: how can I put this in practice ASAP?

The solution is surprisingly simple.

  1. Avoid last minute cramming, because cramming (mass learning) has exactly the opposite function to the spacing effect. It only aids short term memory retention. Yes, congrats, you have passed this quiz on human anatomy, since you pulled an all nighter the night before. But, what’s the whole point of the quiz if you forget this piece of basic yet important information during clinical diagnosis?
  2. Utilise programs that already have automatic spaced repetition algorithms to optimise your learning.. A lot of flashcard apps in the market have already done the hard work for you, for instance, medics favourite — Anki. Do more spaced repetition.
  3. Don’t hate cumulative school final exams. Instead, embrace them, because they force spaced learning to occur.

Of course, revisit this article once in awhile, so that you can retain the information in here about the spacing effect. It might turn out to be useful in med school!





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