Research on Forgetting and Memory
Tony Buzan in his wonderful little book, Learning on Both Sides of the Brain, discusses much of this important history of research on memory.
Hermann Ebbinghaus and his Curve of Forgetting
Hermann Ebbinghaus was an early pioneer in memory research. He conducted experiments on himself, testing how long he could remember long series of nonsense words. This was in Germany between 1879 and 1885. Based on the results, he created a fairly well-known chart called the Ebbinghaus Curve of Forgetting.
Unlike what a students remembers immediately after a lecture, Ebbinghaus always began at 100% memory. He practiced his list of nonsense words until the first time he remembered them perfectly. I suspect his forgetting curve would not have dropped so quickly if he had spent several days repeating the list perfectly.
Notice that the chart is not divided evenly the way graphs should be. To see his first test after 20 minutes, then the test after an hour, it would take a very long chart to reach 31 days. A proper graph would show an even greater memory loss in the first hours and days, and a very gradual loss after that.
As people realized how quickly we forget, they began searching for ways to prevent such rapid memory loss.
Von Restorff pointed out something that should have been obvious. People were asked to learn this list: dog glass flower spoon dress car radio pond Zulu pen ruler bird sheep pencil truth garden. Then they name all the words they remember. Which word is remembered most often? It is the one word that doesn’t fit it: Zulu. The other words are forgettable.
They learned other important information. We normally remember
1. The first several words.
2. The last several words.
3. Words like Zulu that are especially strange, funny, visually powerful, vulgar or different in some way.
4. Words that fit together: If dog, house, bone and leash had been next to each other, we’d remember them.
5. Words with a special meaning to you. If you recently bought a radio, you might remember that word.
People noticed that we remember the first and list items on the list and understood that, when we study for an hour, what we remember most clearly is the first five minutes and the last five minutes (plus anything really unusual or special in between.)
If we divide our study time into two parts, taking a short break between them, we remember the first and last five minutes in each period. We learn twice as much. If we break the study time into four short periods, we remember nearly four times as much. This stops being true if the study time is too short.
It is important to remember: we remember more when we study in several shorter periods of time.
Following this insight came the idea that, if Ebbinghaus had been able to re-learn his list of words before 20 minutes had passed, he wouldn’t have forgotten as much and he could quickly learn 100% again. If, after an hour, he tested himself and studied the words again, he be back at 100% again. Each of these reviews could be a little further apart. But, as long as he continued to review the information, he could almost completely prevent memory loss.
This was the secret tool used by Edward Hughes in Tony Buzan’s book. Here is a chart showing the original Ebbinghaus curve of forgetting in black and the same information with scheduled reviews or rehearsal in red and blue. I have run the line this time to the edge of the chart, perhaps to 6 months.It is this research on forgetting and memory that led Buzan to his concept of Schedules Reviews. If you continue scheduled reviews for a lifetime, you could remember the material you are learning as long as you live.
You might also be interested in the research on short-term and long-term memory in Processing Memory