Last Updated on 2025-05-06 by Clay
Preface
I’ve always tried to keep myself in a state of continuous learning. Yet, there are days when work gets hectic or friends invite me out, and by the time I get home, I’m too exhausted to study. I just play PS5 for a while, take a quick shower, and go to bed. While these days are relaxing and carefree, deep down I worry that if I don’t study regularly, I’ll begin to forget what I’ve learned — just like the saying goes: "Learning is like rowing upstream; not to advance is to drop back."
This anxiety has always lingered inside me. Perhaps it’s something everyone experiences — we study hard and even feel that the knowledge has become our common sense, readying us to dive deeper. Yet, a few months later, we realize we’ve forgotten the details and can no longer explain them clearly to others.
That’s why I originally started writing this blog — to cope with this very problem.
Understanding the “Forgetting Curve”
There’s a well-known theory that human memory follows the so-called “Forgetting Curve”, first proposed by psychologist Hermann Ebbinghaus. For this reason, it’s also called the “Ebbinghaus Curve.”
Ebbinghaus conducted experiments on himself, memorizing meaningless syllables composed of random letters, then testing his ability to recall them at various intervals.
Based on his forgetting patterns, he plotted the following curve (results and image below are sourced from Wikipedia):
- After 20 minutes, 42% forgotten, 58% retained
- After 1 hour, 56% forgotten, 44% retained
- After 1 day, 74% forgotten, 26% retained
- After 1 week, 77% forgotten, 23% retained
- After 1 month, 79% forgotten, 21% retained.
Although his experiments weren’t based on learning different types of knowledge, they do subtly highlight the importance of reviewing — at least that’s how I interpret it.
So, What Can We Do with This Knowledge?
Optimal Learning + Review Strategies
Spaced Repetition
The core idea behind spaced repetition is to review at different, well-timed intervals in order to strengthen memory and reduce forgetting. Since the volume of knowledge we acquire grows continuously, it’s impossible to review everything daily. Thus, the questions become: How often should we review? And when can we stop reviewing?
- Review shortly after the initial learning session (e.g., the next day)
- Gradually increase the interval between reviews (e.g., 3 days, 7 days, 14 days)
- Focus more on the hardest-to-remember content during each review
- Use memory tools like Anki or SuperMemo to automate optimal review timing
Active Recall
Core concept: Actively retrieve information from memory, rather than passively rereading notes.
- Try recalling learned material from memory instead of immediately looking at the answer
- Use self-questioning techniques like: “What is the key idea behind this concept?” or “Why is this formula derived in this way?”
- Apply the Feynman Technique: explain the concept in your own words and make it as simple as possible
Among these, I find the Feynman Technique to be the most profound: If you can't explain a concept in simple terms, then you don’t truly understand it.
As a child, I believed some people were just born geniuses — they could grasp anything instantly. But growing up and meeting many intelligent people, I came to realize that true prodigies who can just "jump to the end" are actually rare (at least I’ve never met one). Most so-called geniuses have very clear mental connections between pieces of knowledge. They can reason their way from point A to point B by understanding the principles and the why behind the process. On the other hand, the knowledge I tend to forget is usually the kind I memorized by rote, without understanding the deeper reasoning that connects the dots.
That’s also why discussing and explaining things to others is so beneficial — others often ask about things we might’ve skipped, prompting us to reflect and fill in the gaps in our understanding.
In short, learning is not just about remembering. It’s about being able to apply knowledge flexibly. Through spaced repetition, active recall, and consistent discussion, we can gradually transform knowledge into a real part of ourselves.
Currently, I use RemNote to record all kinds of content that I need to review repeatedly and be quizzed on by the system. The better notes I save to my local Obsidian (a note-taking app I also use for novel writing and journaling). This setup lets me use RemNote’s cross-platform draft support and integrated flashcard-based SRS (Spaced Repetition System) functionality across PC, tablet, and mobile. I used to use HackMD for this, but now I feel RemNote fits better.
Some of the articles I want to share will also be posted here on this blog — that’s my current plan.