Why Most Studying Is Inefficient
Consider a familiar scenario: you spend an entire Sunday cramming for a Monday exam. You perform reasonably well. Two weeks later, you can barely remember half of what you studied. This is the forgetting curve in action — a phenomenon first described by psychologist Hermann Ebbinghaus in the 1880s that remains as relevant as ever.
Ebbinghaus demonstrated that memory decays in a predictable, exponential pattern after initial learning. But he also discovered something more actionable: reviewing information at the right moments can dramatically flatten that curve. This is the foundation of spaced repetition.
What Is Spaced Repetition?
Spaced repetition is a learning technique where you review material at increasing intervals over time, timed to occur just before you would naturally forget it. Rather than reviewing everything every day (inefficient) or reviewing it once and never again (forgetting), you space reviews strategically.
A simplified example for a new vocabulary word:
- Learn the word on Day 1
- Review on Day 2
- Review on Day 5
- Review on Day 12
- Review on Day 28
- Review on Day 60...
Each successful review reinforces the memory and pushes the next review further into the future. Items you find easy get reviewed infrequently; items you struggle with come back sooner. Over time, the same knowledge requires less and less total study time to maintain.
The SM-2 Algorithm and Modern Software
The most widely used algorithm underlying spaced repetition software today traces back to Piotr Woźniak's SM-2 algorithm, developed in the late 1980s. This algorithm calculates the optimal interval between reviews based on how confidently you recalled each item.
Today, this is automated by tools like:
- Anki: The most powerful and customisable spaced repetition app, free on desktop and Android, with a vast community sharing pre-made decks.
- RemNote: Combines note-taking with built-in spaced repetition, ideal for students who want to study directly from their notes.
- Mochi: A cleaner, modern interface for spaced repetition flashcards.
- Quizlet: Includes a spaced repetition mode in its "Learn" feature.
What Spaced Repetition Is Best For
Spaced repetition excels at any domain requiring memorisation of discrete facts or concepts:
- Language learning (vocabulary, grammar rules, kanji)
- Medical and law school (anatomy, case law, drug interactions)
- History and geography (dates, names, locations)
- Science (formulas, definitions, processes)
- Professional certifications (technical terminology, protocols)
It is less suited to complex procedural skills (like writing essays or solving novel maths problems), which require practice and application rather than recall alone.
How to Get Started Today
- Download Anki (free at apps.ankiweb.net) or open Quizlet in your browser.
- Create a small deck of 20–30 cards on a topic you're currently learning. Keep each card to one specific fact or concept.
- Review daily — even 10–15 minutes per day is enough to maintain hundreds of cards over time.
- Be honest when rating your recall. The algorithm only works if you accurately report whether you remembered something easily, with difficulty, or not at all.
- Add new cards gradually. Avoid adding hundreds of cards at once — you'll create an unmanageable review backlog.
The Long-Term Payoff
The true power of spaced repetition reveals itself over months and years, not days. Medical students who use Anki throughout their studies report being able to recall material from their first year reliably years later. Language learners maintain thousands of vocabulary words with a modest daily investment of time.
In a world where information is abundant but retention is rare, spaced repetition is one of the most evidence-backed tools available to serious learners. The earlier you start, the greater the compounding benefit.