Sure as the mountains wear down, we all forget what we once knew. Though we generally forget quite a bit faster than mountains wearing down! The famous “Ebbinghaus forgetting curve” measures just how fast we forget.
I’m going to explain what Ebbinghaus’ curve is, and what you need to know about how it works, including the fascinating but terrible consequences of when the mechanism of “forgetting” breaks down!
With all that in mind, I’ll make sure you’ve got the tools for overcoming the forgetting curve when you’re studying, by showing you how to do spaced repetition, and making sure that what you learn sticks for good.
What is the Ebbinghaus forgetting curve?
You may think that your forgetful memory is a curse – but spare a thought for Jill Price (originally anonymised as “Patient AJ”), who can’t forget – her memory is “nonstop, uncontrollable, and automatic”, remembering vast amounts of information about her past with considerable accuracy. All that remembering soaks up huge amounts of her time, and causes her substantial distress, as she is constantly bombarded – tormented, even – by her memories whether she wants them or not (scientific article here, and her book here).
For the rest of us, we gradually forget what we know – that is to say, we can longer recall information we learned (if you’re studying psychology and want to nerd out on what “forgetting” actually means to psychologists, check out this article).
From 1880 to 1885, German psychologist Hermann Ebbinghaus ran a series of experiments on himself to figure out how fast he forgot things, by studying a series of nonsense syllables, and getting himself to remember them later.
He found that immediately after learning, his memory of the nonsense syllables was reasonable (nearly 60% right), but after a month, he could barely get more than 20% right.
This curve was drawn using Ebbinghaus’ original forgetting curve data – but that data only came from one man (himself), and a one-person study doesn’t make for great science. Happily, more recent work with a larger sample of participants has been able to replicate the finding.
(If you’re a math nerd and want some meaty discussion about the formula for the curve, check this out.)
Overcoming the forgetting curve with spaced learning
Ebbinghaus, and psychologists since, have identified a number of factors that will “slow the forgetting” – meaning you can remember for longer:
- Is the material related to what you already know? Can you make associations with something already in your memory?
- What format was the information presented in? Words, pictures, audio?
- How much attention were you paying?
- Were you rested and have you slept since?
But perhaps most usefully of all, simply re-studying the material at intervals means you can remember much more, for much longer:
This isn’t just about the number of repetitions you get under your belt: it’s no good to get all your repetitions in on a single evening. There has to be clear blue water in the form of elapsed time between the different learning sessions.
This effect is very robust, and has been replicated across a huge variety of circumstances and types of learning materials (for good reviews of the evidence in humans, see here or here – and it even works in animals!).
Retrieval practice + spaced learning = memory magic
So what should I actually be doing in each of these study sessions?
Most of the time, retrieval practice. If you don’t know what retrieval practice is or how to unleash its incredible power to greatest effect in your studies, check out my previous article for all you need to know on retrieval practice and how to memorise for exams.
Retrieval practice and spaced learning are like hot chips and salt. Like strawberries and cream. Like ice cream and hot chocolate sauce. Both are excellent ingredients in their own right, and to be highly recommended.
But put them together, and something magical happens.
For any aspect of your studies that involves committing things to memory – learning vocabulary and grammar; tables and diagrams; names and dates; definitions; formulas; facts; lists; numbers; processes – you should predominantly be using retrieval practice and spacing together.
Do retrieval practice sessions, but space out your retrieval practice on a single topic over multiple days.
Find out more about how to use spaced repetition in your studies here.