Spacing and testing: psychology-backed methods that increase knowledge retention

Our new smart practice feature, aimed to help students retain knowledge, is based on spacing and testing. Learning expert Olav Schewe looks into the science behind these learning methods and explains why they’re so effective.

April 15, 2019

Olav Schewe, learning expert and popular speaker, worked with us as a pedagogy advisor whilst we were developing our new smart practice feature. Initially an average student, Olav became high school valedictorian and graduated top of his class at the University of Oxford. He described the techniques that helped him achieve that in his book Super Student: How to Save Time, Learn More Effectively and Get Better Grades, now translated into 16 languages. In a series of articles on our blog, Olav looks into the science of spacing and testing that our smart practice is based on, and discusses how Kahoot!, combined with these learning methods, can help students retain more knowledge.


Remembering what we’ve learned in classroom beyond it, is one of the core goals of learning. Our memory not only helps us retain knowledge, but also retrieve it in the future so we can apply it to practical problems.

However, many common learning techniques, for example, cramming and consuming content in “bulk” sessions, aren’t optimal when it comes to retaining knowledge. They do help us in the short term, but a lot of acquired knowledge fades over time.

My search for more productive learning methods started when I was in junior high school. Being an average student, I challenged myself to try new ways to learn and see if they’d improve my performance. I found many answers and solutions in cognitive psychology, a branch of psychology that studies memory, motivation, attention, problem solving and creativity. Among the methods that helped me get from average scores to the top of class, were spacing and testing that I’ll talk about in this article. They will prove useful for learners of any age and in any context, not only a school or university setting.

Spacing effect: learn smarter, not harder

Learning productively isn’t about working hard for a long time – it’s about using a smart approach! That’s when spacing comes into play.

We remember information more easily and retain it for a longer time when we learn it in multiple, spread-out sessions

This method challenges time-consuming and sometimes stressful routines such as re-reading, cramming, and tedious, single-minded repetition. Psychologists have found that we remember information more easily and retain it for a longer time when we learn it in multiple, spread-out sessions, rather than in one big session or sessions very close to each other in time. You wouldn’t expect to build strong muscles from one long and intense workout – instead, you’d work out in shorter sessions every few days. Our brain actually works in a similar way, this is why the best way to build strong neural connections is to spread out your practice.

Spacing effect: we remember information more easily and retain it for a longer time when we learn it in multiple, spread-out sessions.

The spacing effect is, in fact, one of the oldest findings in experimental psychology: it was first described in 1880s by Herman Ebbinghaus, and a large volume of research has confirmed its efficacy since then.

Ebbinghaus spent years memorizing syllables he made up, and recording results to analyze his memory. One of the experiments he ran during his research was comparing whether he’d remember more syllables by doing 68 repetitions one day, then 7 the next, or just 38 repetitions spaced out over three days. He achieved the same results with both approaches, but it took way less time and effort when repetition was spaced out.

In practice, some examples of using spacing in class can be: revisiting old topics some time after they were taught, mixing up tasks or problems related to different topics, incorporating some tasks related to old topics into future homework, and giving frequent, low-stakes tests. The latter takes us to the next powerful learning method:

Long live tests!

Let’s face it – tests don’t have the best reputation with students (probably not with some teachers either). They’re often perceived as a summative assessment tool, connected with stress and effort needed to remember a big volume of content by a specific date.

However, this is not the only way tests can be used in education. Another lesson from cognitive psychology is that tests are a powerful learning – not just assessment – tool, when used frequently and shrewdly. This leads us to the testing effect:

Testing effect: Using tests for practice after knowledge is obtained helps us retain it for a longer time.

In this case, a test has nothing to do with scores – it’s a practice tool to help students find out what they don’t know yet and what they need to study more. When the pressure is low, i.e. scores are removed, and testing happens frequently, students don’t even need to prepare – it becomes an expected part of the learning and review process.

Some of the most known studies on the testing effect have been run by psychologists Henry Roediger and Jeffrey Karpicke. In one such study, they ran experiments with groups of high school students who studied content through re-reading and compared them to groups who studied with repeated testing. The study revealed that students who took tests recalled much more after a week than students in a repeated-study condition (61% vs. 40%), even though students in the former condition read the text 3 times vs 14 times in the other group.

Advantages of frequent testing

Frequent testing has many advantages both for teachers and students:

  • It helps students identify what topics need more work.
  • It makes studying more efficient.
  • It improves long-term knowledge retention.
  • It takes the stress out of testing when it becomes a frequent exercise.
  • For teachers, it provides actionable feedback, revealing topics that need reinforcement.

Testing effect: Using tests for practice after knowledge is obtained helps us retain it for a longer time

When students answer test questions on a topic they learned some days or weeks ago, they’re using both spacing and testing. And when the testing is done without pressure, i.e., when it’s not tied to any formal grading, it gives students a quick snapshot on how well they remember learning content and what requires more learning focus.

Kahoot! is a great tool for combining spacing and testing – where a test would come in the form of an interactive, stress-free and engaging quiz, to give students instant feedback on how well they remember learning content.

Next up: how to put the spacing and testing effects to action with Kahoot!, including the smart practice feature.

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