It is called a forgetting curve and shows how quickly we forget something we have learned. Just enter "forgetting curve" into Google Images for many examples. The curve was first established by Herman Ebbinghaus experimenting on himself using nonsense syllables. However, it seems like the general shape of the curve is true for a large range of different subject matter and conditions - and that fits in with our everyday experience. The key points are:
- you forget most soon after learning
- the curve flattens out so that the stuff you do retain you forget more slowly
- you can change the shape of the curve with revision and recall
There is a slighty different shaped forgetting curve in use:
which suggests that we can actually remember more a short period (e.g. 10 minutes) after learning something than we can remember immediately afterwards. I got this from Tony Buzan books such as "Use your head" and "Speed Memory" and I have faithfully reproduced it in my courses. It has some interested consequences for an instructor. For example, it might be more effective to finish a presentation, take a short break, and then summarise - rather than the traditional order of summarise and then take a break.
Yesterday I noticed that this "Tony Buzan" shape is not mentioned in any of my more academic books on memory. So I thought I would track down the original research on which it is based. Several frustrated hours later I gave up. The Buzan books do not give academic references - they just use phrases such as "studies show". Google threw up several places where this shape of curve was used - some quite respectable but they all seemed to come back to Buzan. I tried using various academic databases to search the voluminous literature on memory and forgetting - but they all came back to the Ebbinghaus shape not the Buzan shape.
I don't know that it makes a lot of difference for teaching or learning in practice. You still need to review regularly to avoid forgetting. But it frustrates me - especially as I have believed and repeated the Buzan line for nearly 30 years now.
So, if anyone reads this and knows of evidence for the Buzan curve or knows there is no such evidence - I would really like to hear from them.
Meanwhile I will treat is slightly differently when it comes up on my course.