The Forgetting Curve
Why We Forget, and What We Can Do About It
Forgetting can be infuriating, particularly when you're trying to learn a new skill or absorb vital information. When you can't recall the knowledge you need, stress can build and your confidence can take a knock. It may even lead to wasted time, missed opportunities, and costly mistakes.
But when you understand why you forget, you can take steps to prevent it, and make sure that what you learn, sticks!
In this article, we explore The Forgetting Curve, an enduring model that demonstrates how memories are lost over time and what we can do to reinforce the things that we learn, so that we can remember them more effectively.
The Importance of Not Forgetting
Memory is important for our survival. Our brains are good at storing information that helps us to avoid physical or psychological harm.
We are particularly good at remembering the things that we need to know – details that are of vital importance to our survival. For example, foods we should avoid, pathways or areas we should stick to, and the people who are important in our lives. We also tend to remember experiences that trigger powerful emotions – such as surprise, fear, success, or relief – for longer.
But this means that many of the things that we want to learn (or that others need us to know) can drop out of our memory all too easily.
This is where the Forgetting Curve comes in!
What Is the Forgetting Curve?
German psychologist Hermann Ebbinghaus wanted to understand more about why we forget things and how to prevent it. His research produced the Forgetting Curve – a visual representation of the way that learned information fades over time (see figure 1, below). 
Ebbinghaus experimented with his own ability to remember using a list of nonsense syllables, which he attempted to recall after different lengths of time. His experiences and results revealed a number of key aspects of memory:
- Memories weaken over time. If we learn something new, but then make no attempt to relearn that information, we remember less and less of it as the hours, days and weeks go by.
- The biggest drop in retention happens soon after learning. This is reflected by the steep fall at the start of the Forgetting Curve (see figure 1). Without reviewing or reinforcing our learning, our ability to retain the information plummets. For example, you may leave a webinar or meeting with your head full of new facts and figures, only to find that you can remember very little of it just hours later.
- It's easier to remember things that have meaning. Things with little or no meaning (like the nonsense syllables Ebbinghaus tried to learn) conform most closely to the Forgetting Curve. So, for instance, if you're listening to a talk on a subject that you don't really understand or have little interest in, you'll likely forget it faster than if it were on a subject that you found really engaging or exciting.
- The way something is presented affects learning. The same set of information can be made more or less memorable, depending on how well it's communicated. You'll likely find it easier to remember something that's been organized logically and presented clearly. But you may well forget that haphazard, scribbled shopping list!
- How you feel affects how well you remember. Ebbinghaus believed that physiological factors, such as stress and sleep, play a significant part in how well we retain information. Many people experience this as a vicious cycle – they feel stress, which makes it harder to remember, creating even more stress. There's also strong evidence to suggest that sleep can help our brains to sort and store information. 
Figure 1 – The Forgetting Curve
Ebbinghaus's research dates back to the 1880s, but it is still widely used and highly regarded. In 2015, a research team successfully reproduced his findings, and concluded that his methods and theories still held true. 
Worried About Forgetting?
Some aspects of memory can change with age. Your short-term memory may feel weaker, for example, and it can be more challenging to learn completely new things. But Ebbinghaus's work showed that sensible strategies and good self-care can help to keep your memory strong.
Aside from aging, a number of other physical and mental factors can alter how you think and learn. If you're ever worried about a change in your memory, be sure to seek medical advice.
How to Prevent Forgetting and Boost Your Memory
It's tempting to think that Ebbinghaus's work paints a bleak picture of learning. But it's not all negative. In fact, his research highlighted several things that we can do to retain information for longer. In this section, we look at four strategies you can use to improve your power of recall:
1. Use "Spaced Learning"
The most important discovery Ebbinghaus made was that, by reviewing new information at key moments on the Forgetting Curve, you can reduce the rate at which you forget it!
This approach is often referred to as "spaced learning" or "distributive practice."  (See figure 2, below.)
Figure 2 – Using Spaced Learning to Combat the Forgetting Curve
Even though our memory fades quickly, a review session soon after the original learning can improve it. This session should happen when recall has slipped significantly, but hasn't fallen so low that you're essentially starting over.
Reviewing and refreshing information regularly halts the Forgetting Curve. (In figure 2, the dotted part of each curve shows what would likely happen otherwise.) And, although forgetting starts again after each review session, it's slower than before. That's why each new curve shown in figure 2 is shallower than the last.
The gaps between your review sessions can be longer as time goes on. So, you might refresh your learning from a lecture the following day, then two days later, then after a week, then after 30 days… and you'll still know all the key information a month on! Reviewing information like this, at strategic points after you originally learned it, will stretch your recall and strengthen the memories encoded in your brain. You'll also discover any gaps that you need to focus on and relearn, if necessary.
Exactly how you time and space your review sessions will depend on a number of factors: the type of material you're learning, how much detail you need to know, and how long you want to keep it fresh in your mind. And, if other information disrupts or distracts you, you'll likely have to put in more work to keep your learning strong.
Another strategy Ebbinghaus explored was "overlearning" – that is, putting in more than the usual amount of effort when you learn something. He found that doing this improved retention, and slowed the steep drop seen on the Forgetting Curve.
He also pointed out that, by using certain memory strategies, we can improve our chances of retaining even hard-to-learn information.
See our article, Memory Improvement Techniques, for a range of tried-and-true "mnemonic" techniques that can help you to improve your power of recall.
3. Make Information Meaningful
Do everything you can to make the material that you need to learn clear, relevant and purposeful, and establish a strong reason for retaining it. The more you know how something will benefit you in the long term, the more likely your memory will prioritize it.
Reducing distractions and other demands – known as your "cognitive load" – should also help with this.
4. Keep Challenging Your Memory
If you come to review some information and discover gaps in your memory, don't despair! This is the most productive time for stretching your recall. Learning done at this point will be all the stronger because of the mental challenge involved.
If you're imparting learning or information to an audience, or delivering training, make it as interactive as possible. Even just asking questions will encourage people to sort and strengthen the information in their minds.
The Forgetting Curve, or the Ebbinghaus Curve of Forgetting, is an influential memory model. It shows how learned information slips out of our memories over time – unless we take action to keep it there.
The steepest drop in memory happens quickly after learning, so it's important to revisit the information you've learned sooner rather than later. After that, regular reviews will help to reinforce it. But you can leave longer and longer gaps between these review sessions. This is known as "spaced learning."
Doing this will help to reinforce your learning and improve your power of recall, so that you can remember what you've learned in the long term. Other strategies you can use to improve your memory are: overlearning information, making what you want to learn meaningful, and challenging your memory regularly.
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