Your Brain Needs to Forget Before It Can Remember
Hermann Ebbinghaus proved in 1885 that you lose 56% of new information within an hour. That's not a bug. It's how durable memory gets built.
In 1885, a German psychologist named Hermann Ebbinghaus memorized lists of nonsense syllables. DAX. BUP. ZOL. Sounds chosen specifically because they carried no prior associations. Then he tested himself at intervals to see how much he retained.
The results were brutal.
56% gone within one hour. 66% within a day. 75% within six days. He called it the forgetting curve, and it's been replicated so many times in the 141 years since that it's basically a law of how human memory works.
Your brain throws away most of what you learn almost immediately. That feels like a problem.
It's not.
The Spacing Effect
Ebbinghaus discovered something else in that same research. When he spread practice sessions over time instead of cramming them together, retention improved dramatically.
This is the spacing effect. It might be the most well-supported finding in experimental psychology. Dempster called it exactly that in 1988, pointing out how strange it was that such a reliable phenomenon had been almost completely ignored by educators.
In 2006, Cepeda, Pashler, Vul, Wixted, and Rohrer ran a meta-analysis of 254 studies involving over 14,000 participants. Spaced practice beat massed practice in nearly every case. Studying for next week? Space sessions one to two days apart. Need it a year from now? Gaps of several weeks worked best.
Kornell (2009) showed that simply spreading flashcard sessions across multiple days improved long-term retention by 47%. Same material. Same total study time. Just distributed differently.
Why Forgetting Is the Point
Elizabeth Bjork and Robert Bjork at UCLA proposed a framework in 2011 that explains why spacing works. Two types of memory strength. Storage strength is how deeply embedded a memory is. Retrieval strength is how easily you can access it right now.
They often move in opposite directions.
When you cram, retrieval strength is high. You just studied it. It's right there. You feel like you know it. But storage strength stays low because you never had to work to retrieve it. You kept refreshing the memory before it could fade.
When you space your practice, retrieval strength drops between sessions. You forget a little. And when you sit down again and successfully pull that information back from the edge of being lost, storage strength increases far more than if the retrieval had been easy.
The struggle of remembering is what makes the memory stick. Cramming skips that struggle entirely. It feels productive. It's almost useless for long-term retention.
The Testing Effect
Roediger and Karpicke (2006) ran a study where students either reread a passage or read it once and then took a practice test. After five minutes, the rereading group performed slightly better. After one week, the testing group crushed them.
The students taking the practice test felt like they were doing worse during the session. They were struggling. It produced dramatically better results.
Karpicke and Blunt (2011) published a study in Science comparing retrieval practice to elaborative concept mapping. Retrieval practice still won, by 50% on a final assessment one week later.
The strategies that feel productive, rereading, highlighting, reviewing notes, produce a feeling of fluency that is almost entirely an illusion. The strategies that work feel frustrating and slow and wrong.
Unsuccessful Retrieval Still Works
Kornell, Hays, and Bjork (2009) found something stranger. When people attempted to retrieve information and failed, they still learned more than people who simply studied the answer. The unsuccessful attempt itself primed the brain to encode the correct answer more deeply when it was finally revealed.
Trying to remember something and getting it wrong is better for learning than never trying to remember it at all.
Manu Kapur's work on productive failure (2008, 2014) showed the same pattern in classrooms. Students who struggled with problems before receiving instruction outperformed students who received instruction first. The struggle built the scaffolding that made the eventual instruction stick.
What This Looks Like in Practice
I used to study the way most people study. Read the material. Reread the parts I didn't get. Highlight, review, run through everything the night before. Felt productive every single time. I forgot almost all of it within two weeks.
Spaced repetition software like Anki implements algorithms based on Ebbinghaus and the Bjorks. It schedules reviews right as the memory is about to slip away. Too early and the retrieval is too easy, no storage gained. Too late and there's nothing left to retrieve.
You don't need software. Kornell's flashcard study showed that just spreading sessions across days produced that 47% improvement. No algorithm required. Just the discipline to stop studying when it still feels like you need more reps, and come back tomorrow.
The hard part isn't the technique. It's trusting the technique works when every instinct is screaming that walking away while you still feel uncertain is irresponsible.
That uncertainty is the signal that learning is happening. Schmidt and Bjork (1992) called these "desirable difficulties." The difficulty is the mechanism, not an obstacle to it.
The Illusion That Won't Die
Despite over a century of evidence, most students still cram. Most professionals still binge-learn before certifications. Most training programs still front-load information and call it development.
Dempster (1988) wrote an entire paper on this, calling the spacing effect "a case study in the failure to apply the results of psychological research." We've known about this since 1885. We've confirmed it in hundreds of studies. We still don't use it.
Massed practice feels better. The familiarity feels like knowledge. But it's retrieval strength, not storage strength. It evaporates in days.
Spaced practice feels uncertain. You forget things between sessions and that forgetting feels like failure. Your brain is telling you the strategy isn't working at the exact moment it's working the most.
That's the practice paradox in its purest form. The forgetting is the learning.
Sources
- Ebbinghaus, H. Über das Gedächtnis (1885) (opens in new tab)
- Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. "Distributed Practice in Verbal Recall Tasks" (2006, Psychological Bulletin) (opens in new tab)
- Dempster, F. N. "The Spacing Effect: A Case Study in the Failure to Apply the Results of Psychological Research" (1988, American Psychologist) (opens in new tab)
- Bjork, E. L. & Bjork, R. A. "Making Things Hard on Yourself, But in a Good Way" (2011, in Psychology and the Real World) (opens in new tab)
- Kornell, N. "Optimising Learning Using Flashcards" (2009, Applied Cognitive Psychology) (opens in new tab)
- Roediger, H. L. & Karpicke, J. D. "Test-Enhanced Learning" (2006, Psychological Science) (opens in new tab)
- Karpicke, J. D. & Blunt, J. R. "Retrieval Practice Produces More Learning than Elaborative Studying with Concept Mapping" (2011, Science) (opens in new tab)
- McDaniel, M. A., Agarwal, P. K., Huelser, B. J., McDermott, K. B., & Roediger, H. L. "Test-Enhanced Learning in a Middle School Science Classroom" (2011, Journal of Educational Psychology) (opens in new tab)
- Kornell, N., Hays, M. J., & Bjork, R. A. "Unsuccessful Retrieval Attempts Enhance Subsequent Learning" (2009, Journal of Experimental Psychology: Learning, Memory, and Cognition) (opens in new tab)
- Kapur, M. "Productive Failure" (2008, Cognition and Instruction) (opens in new tab)
- Kapur, M. "Productive Failure in Learning Math" (2014, Cognitive Science) (opens in new tab)
- Schmidt, R. A. & Bjork, R. A. "New Conceptualizations of Practice" (1992, Psychological Science) (opens in new tab)
Part of the Practice Paradox series. Previous: 93% of Teachers Believe a Myth. Next: Stop Rereading. You're Just Feeling Smart..
