Core Learning Techniques,
Explained in Full

Spaced Repetition

In 1885, German psychologist Hermann Ebbinghaus published what he called the forgetting curve — a mathematical description of how quickly memories decay without reinforcement. His data showed that roughly 50% of new information is forgotten within an hour, 70% within 24 hours, and nearly 90% within a week, assuming no review takes place.

The solution he identified — and that modern cognitive science has thoroughly confirmed — is spaced repetition: reviewing material at intervals timed to catch it just before it would otherwise be forgotten. Each successful retrieval resets and steepens the forgetting curve, so the next optimal review comes later. Over time, the gaps between reviews stretch from hours to days to weeks to months, until the knowledge is essentially permanent.

How Spaced Repetition Works in Practice

The simplest manual approach is the Leitner box system, which uses physical index cards sorted into groups by review frequency. Cards you know well move to less-frequent boxes; cards you struggle with stay in the daily review pile. This analogue method requires no technology and works extremely well for vocabulary, historical dates, formulae, and any material that can be expressed as a question–answer pair.

Digital implementations — Anki being the most widely used — automate the scheduling through a spaced repetition algorithm (SuperMemo-2 being the most researched). The software tracks your performance on each card and calculates exactly when each one should next appear. A well-built Anki deck can bring retention rates above 90% on hundreds of cards reviewed in just 20 minutes a day.

The Most Common Spaced Repetition Mistakes

The biggest error is creating cards before truly understanding the material. Spaced repetition helps you remember; it does not help you understand. Feed it poorly understood concepts, and you will memorise gibberish. Always learn first — through reading, lectures, or the Feynman Technique — and only then create cards to cement that understanding over time.

A secondary mistake is over-engineering cards. Effective cards are atomic: one question, one answer, no ambiguity. Cards that ask you to explain a multi-step process are almost always better split into individual component cards. The goal is instant, unambiguous retrieval — not mini-essays.

Active Recall

If spaced repetition is the when of effective study, active recall is the what. The core principle is disarmingly simple: instead of reviewing material by looking at it, review it by looking away from it and attempting to reconstruct it from memory.

This distinction — between recognition and retrieval — has enormous consequences. Recognition is what happens when you re-read a page: your brain sees the words, confirms "yes, I've seen this before," and feels satisfied. Retrieval is what happens when you close the book and attempt to write down everything you remember: your brain has to actually rebuild the knowledge structure from scratch, reinforcing the neural pathways that allow future recall.

The 2006 study by Roediger and Karpicke at Washington University is perhaps the most cited demonstration of this effect. Students who studied a text once and were tested on it recalled 50% more information a week later than students who re-studied the text three additional times. More study, less learning — a counterintuitive result that has since been replicated dozens of times.

Practical Active Recall Methods

The blank page method: After a study session, take a clean sheet of paper and write everything you can remember about the topic without looking at your notes. Then compare what you wrote against the source material. The gaps between the two are your study targets for next time.

Question-based notes: As you read or listen, convert the key points into questions in the margin. Before your next study session, cover the answers and attempt to answer each question from memory. This is essentially the Cornell Notes system formalised into a retrieval practice.

Flashcard retrieval: Traditional flashcards are an active recall tool when used correctly. The key word is "correctly" — the card must be turned face-down and the answer generated before flipping. Shuffling through cards while looking at both sides simultaneously is passive review dressed up as active recall.

Practice problems over example review: In STEM fields, working through unsolved problems is vastly more effective than re-reading worked examples. Even an incorrect attempt strengthens the memory for the correct approach more than passive review does.

Why Active Recall Feels Uncomfortable — and Why That Is the Point

Active recall is harder than re-reading. That difficulty is not a bug — it is the mechanism. Cognitive scientists call this desirable difficulty: the extra mental effort required to retrieve information is precisely what causes stronger encoding. If a study method feels effortless, it is almost certainly not working.

Richard Feynman, one of the twentieth century's most celebrated physicists, was known not just for his brilliance but for his ability to explain complex physics in language that anyone could follow. He maintained that if you could not explain something simply, you did not truly understand it — and he practiced this belief relentlessly, teaching himself topics by pretending to explain them to a complete novice.

The Feynman Technique is a four-step process for deep understanding:

The Feynman Technique is particularly valuable in two specific situations. The first is when starting a new complex topic: working through a Feynman explanation of the foundational concepts before doing any rote memorisation ensures that what you memorise has a meaningful structure to attach to. The second is in exam preparation, where it rapidly identifies which areas of apparent knowledge are actually vague recollections rather than genuine understanding.

Feynman and the Fluency Illusion

The Feynman Technique works as a direct antidote to the fluency illusion. When you read a textbook chapter, the ideas feel familiar — after all, the author understands them and explains them fluently. Your brain borrows that fluency and mistakes it for its own. The moment you close the book and try to explain the concept yourself, the illusion dissolves instantly.

This is not a comfortable moment. Most people instinctively reach back toward the textbook, which is exactly the wrong response. Instead, sit with the discomfort of not knowing, write what you do know, identify the holes precisely, and then — and only then — consult the source material to fill those specific gaps. The combination of productive struggle followed by targeted reading is extraordinarily powerful.

Combining Feynman with Active Recall

These two techniques complement each other naturally. Use the Feynman Technique for initial understanding and for complex, interconnected concepts. Use active recall for cementing facts, definitions, and procedures that have already been understood. Together, they cover both the understanding and the retention dimensions of learning — the two things that must happen for knowledge to be genuinely usable.