The Science of Forgetting: Why We Lose Knowledge and How to Retain It
I'm sure that at some point in your life, you've read a book, watched a lecture, taken a course, or written something down, only to realise weeks later that you remember almost nothing. This is a universal human experience that causes significant frustration for anyone trying to learn something new or retain important information.
Unfortunately, when this happens, most people just believe they have a poor memory. But this is simply not the case. Forgetting is not a sign of a poor or weak memory; instead, it's a pivotal function of the human brain. In fact, without the brain's ability to forget, we wouldn't be able to focus, prioritise, or effectively adapt to new information.
So, if the brain is partly wired to forget, how can we ensure that we retain the information we need when learning something new? The answer lies in understanding the basics of the neuroscience of memory and applying strategies rooted in neuroscience to counteract the forgetting process.
Why Do We Forget?
The human brain is not designed for perfect recall. In fact, very little of our past experiences can be recalled correctly. Instead, our brains are optimised for efficiency. Our ability to forget helps the brain clear out irrelevant information and allows us to focus on what is most important. In this context, your brain can be thought of as a highly effective hard drive that deletes old information that is no longer required or relevant to us (i.e., hasn't been accessed on the hard drive for a long period of time) to ensure that its storage capacity doesn't max out.
However, forgetting is not just an unfortunate side effect of learning; it is an essential part of how memory works. But why do we forget some things quickly while others remain with us for years? The answer lies in several key mechanisms.
1. The Ebbinghaus Forgetting Curve
Ebbinghaus Forgetting Curve (Source)
German psychologist Hermann Ebbinghaus was one of the first to study how quickly we forget information. His research showed that memory loss follows a remarkably predictable pattern: almost 50% of new information is lost within the first hour, up to 70% within a day, and up to 90% within a week unless that information is reinforced. This rapid loss of new information helps explain why you might remember something for an exam but forget it a week later. Without reinforcement of some kind, the majority of new knowledge will be lost.
2. Interference: The Battle for Memory Space
Our brains are constantly processing new inputs. If similar pieces of information overlap to some extent, they can interfere with each other, making older memories harder to retrieve. This is why learning multiple similar things at once can be confusing if not structured correctly. For example, if you're learning two languages at once or studying multiple historical events simultaneously, confusion is easily caused as the memory pathways become confused due to the brain's perception of information overlap. Aspects of the information will be retained from one language or event, and other parts will be forgotten and vice versa.
Think of it like trying to listen to two conversations at once; it's hard to keep track of what's being said in each conversation.
3. Lack of Meaning or Connection
The brain prioritises information that is perceived as useful, meaningful, or emotionally significant. Abstract facts that have no overlap with any previous information stored in the brain are far more likely to be forgotten. This is why we remember emotionally significant moments vividly but struggle to remember facts from a textbook. When information doesn't fit into an existing mental framework, it is forgotten quickly.
For instance, you might remember a song's lyrics from years ago because it was tied to a memorable event or emotion.
4. Weak Storage and Retrieval Pathways
At the most basic level, memories are stored through connections between brain cells. If these pathways are not reinforced through repetition or use, they weaken over time. It's not that the information has disappeared during this weakening of connection, but it becomes increasingly difficult to activate, and thus that information becomes more difficult to retrieve. This is why when you take a break from learning skills like playing the guitar or piano, you regress. It isn't that the pathways have disappeared, but they have become harder to access.
How to Retain Knowledge More Effectively
Forgetting may be natural, but that doesn't mean retention of information has to be difficult. By leveraging neuroscience-backed strategies, we can significantly improve retention and make learning last.
1. Active Recall: Testing, Not Reviewing
I'm sure you've been there at some point. You've decided to study and aren't exactly sure what to do, so you just re-read your notes or sections that you've previously highlighted. Unfortunately, passive methods like this are among the least effective ways to learn. Instead, you need to use strategies that involve active recall. Active recall forces you to retrieve information without looking at your notes. Testing yourself in this manner strengthens the brain connections related to that information, leading to that knowledge being easy to call upon from your long-term memory.
2. Spaced Repetition: The Power of Timing
Instead of cramming all your review sessions or when you learn new knowledge into one sitting, you should instead space them out. Revisiting information at increasingly longer intervals - after a few hours, a few days, and then weeks - strengthens the brain connections and slows down forgetting. By revisiting them at increasing intervals, you ensure that these pathways are continuously being strengthened and not degrading over time.
3. Encoding: Make it Meaningful
We remember stories and music better than isolated facts. I'm sure you've had the experience of recalling all the lyrics to a song perfectly despite not having heard it for a long time. You don't need to start creating study songs (although you can if you wish), but being able to link that new piece of information to a story to give it meaning is an incredibly powerful technique. Use analogies, create mental images, or explain it to someone else to reinforce your understanding.
4. The Role of Sleep in Memory Consolidation
Sleep is incredibly important for memory consolidation, and most people don't get enough of it, putting themselves at a disadvantage when learning. During sleep, the brain strengthens and recognises memories, transferring them from short-term to long-term storage. Lack of sleep impairs this process, making new knowledge retention difficult. Prioritising quality sleep is one of the simplest yet most effective ways to improve knowledge retention and learning.
Learning that Lasts
Forgetting is not a flaw, it is a feature of how the human brain works. By understanding the mechanisms behind memory loss, and how we form and store memories, we can apply simple yet powerful techniques to retain knowledge more effectively. Whether you are a student, a professional, or a lifelong learner, implementing strategies such as active recall, spaced repetition and meaningful connection will transform your ability to retain information and learn.
The key takeaway - don't fight forgetting, work with it. By strategically reinforcing memories, you can ensure that knowledge doesn't just slip away but becomes part part of your lasting expertise.
