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The Forgetting Curve

Forgotten memory

Hermann Ebbinghaus may not be a name commonly thrown around in educational circles but every teacher is aware of the phenomenon he first described in the 1850s. Through a series of studies, this German psychologist found that people usually forget 90 percent of what they learn in class.

This Forgetting Curve, as he called it, is the decline in the strength of a memory over time. Obviously, this has significant implications for how we design and implement learning opportunities for students. His research further went on to show that most of the forgetting occurs in the first few hours after class.


To help students retain information for the long term, we do such things as spiraling, re-teaching, and spacing the practice of learning over time. When learning is spaced over time, it is more likely to enter long-term memory. Modern neuroscientists continue to study the process of learning and memory. Dr. John Medina, author of Brain Rules, reminds us of the simple but powerful role of repetition to strengthen memory.


Dr. Medina’s recent studies have shown that the time interval between the original learning and the practice is extremely important. In one study, elementary students learned math concepts in the morning and then participated in mini-repeat lessons approximately 90-120 minutes later. Those students who repeated the learning in approximately two hour intervals had an average increase of 14% in recall compared to those students who didn’t repeat at similar intervals.


Dr. Medina also sounds an interesting alarm regarding using homework as practice. If a student learns something in the morning and then doesn’t “practice” that concept or skill until the evening, it cannot be considered practice anymore. It really needs to be considered new learning if it hasn’t been practiced and repeated at appropriate 90-120 minute intervals. In such cases, “Homework is not review, it is new learning,” he explains.


As classroom teachers, conscientiously scheduling recurrent practice of important content has significant implications. Who knows, maybe you’ll see a 14% increase in your students’ performance. (But you may need to reread this again in 2 hours.)

Medina, J. (2008). Brain Rules. Seattle: Pear Press

Bryan Harris, Ed.D. is a trainer/consultant Bryan Harris, Ed.D. has been an educator for over 25 years. He has served as a classroom teacher, an elementary school principal, and a district level director. Now working full time as an author, speaker, and consultant he has trained over 18,000 educators in powerful and effective strategies that increase student engagement and achievement. He is known for his engaging trainings and presentations that demonstrate relevant and practical strategies. He is the author of 5 books including the popular 2010 book Battling Boredom. He holds a Bachelor of Science degree in Education and a Master of Educational Leadership degree from Northern Arizona University. In 2013, he earned a doctorate (EdD) from Bethel University in Minnesota after studying factors impacting new teacher retention. He also holds a certification in brain-based learning from Jensen Learning Corporation. As the author of three highly-regarded books published by Routledge, he has a passion for helping educators discover ways to inspire and engage students.

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