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What is Spaced Repetition?

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Definition​

Spaced Repetition is a learning technique that effectively converts learned information into long-term memory by reviewing it just before forgetting. Based on the "Forgetting Curve" theory discovered by German psychologist Hermann Ebbinghaus in 1885, it's characterized by gradually increasing review intervals over time.

We naturally forget what we've learned as time passes. According to Ebbinghaus's research, 20 minutes after learning, we remember 58%; after 1 hour, 44%; after 1 day, 33%; and after 1 month, only 21%. Spaced Repetition is a scientific learning strategy that prevents this forgetting and consolidates information into long-term memory.

How It Works​

The core of Spaced Repetition is "optimal review timing." Reviewing too frequently wastes time, while reviewing too late means you've already forgotten and must relearn from scratch. This method strengthens memory by reviewing when your brain starts to forget—when retrieval becomes slightly difficult.

Relationship Between Forgetting Curve and Review:

  • Initially, we forget quickly after learning
  • Reviewing makes the forgetting curve gentler
  • The more we repeat, the longer we remember
  • Intervals between reviews gradually increase

Principle of Optimal Intervals: Ideally, newly learned content should be reviewed at these intervals:

  • 1st review: After 10 minutes
  • 2nd review: After 1 day
  • 3rd review: After 3 days
  • 4th review: After 1 week
  • 5th review: After 2 weeks
  • 6th review: After 1 month
  • 7th review: After 3 months

Of course, these intervals can be adjusted based on individual learning ability and content difficulty. Easily remembered content gets longer intervals, while difficult content gets shorter intervals.

Implementation Methods​

Step 1: Prepare Learning Materials​

First, break down the content into small units. Flashcards, question-answer formats, or key concept summaries work well. Don't put too much information at once—one card should contain only one concept.

Step 2: Initial Learning​

Learn new content for the first time. Don't just read—understand it, explain it in your own words, and think of examples. Active learning is crucial.

Step 3: First Review (10 minutes to 1 hour later)​

Conduct the first review shortly after learning. The memory is still fresh, so recall should be easy. Identify what you don't remember and relearn it.

Step 4: Repeat at Intervals​

Use an app or notebook to schedule next reviews. After each review, answer these questions:

  • Remembered easily: Double the interval
  • Remembered with difficulty: Multiply interval by 1.5
  • Didn't remember: Reset interval to the beginning

Step 5: Continuous Management​

Repeat for weeks to months until fully converted to long-term memory. Using apps automatically manages review schedules.

Examples​

Medical Student Kim's Anatomy Study​

Situation: Student Kim needs to memorize 200 bone names

Implementation:

  • Register each bone photo and name as flashcards in Anki app
  • Day 1: Study all 200 cards (about 2 hours)
  • Day 2: Review 150 cards suggested by app (50 well remembered)
  • Day 3: Review 100 cards
  • Week 1: Review 60 cards
  • Week 2: Review 30 cards
  • Month 1: Review 15 cards

Result: Instead of cramming before the exam, investing 15-30 minutes daily resulted in perfect memorization of 200 bone names. The knowledge remained even after the exam, proving useful during clinical practice.

Office Worker Lee's English Conversation​

Situation: Learning business English expressions

Implementation:

  • Learn 5 new business English expressions daily during commute
  • Create cards with example sentences using Quizlet app
  • Review during lunch (1st review)
  • Weekly review on weekends (2nd review)
  • Monthly comprehensive review at month-end (3rd review)

Specific Example:

  • Monday learning: "Let's circle back on this"
  • Monday lunch: Review today's 5 expressions
  • Next Monday: Review 15 expressions the app recommends from last week
  • Month-end: Intensive review of 30 weak expressions from this month

Result: After 6 months, naturally using over 600 business English expressions with increased confidence in meetings with foreign clients.

Programmer Park's Algorithm Learning​

Situation: Learning algorithm patterns for coding tests

Implementation:

  • Organize each algorithm problem type as cards
  • Front: Problem type and key hints
  • Back: Approach method, time complexity, precautions, code snippets

Example Card:

  • Front: "Find indices of two numbers in array that sum to target"
  • Back: "Use hashmap, O(n) time complexity, store seen numbers and their indices"

Review Schedule:

  • Day 1: Learn 10 new algorithm patterns
  • Day 2: Review yesterday's patterns + 10 new patterns
  • Day 4: Review patterns from 2 days ago + new patterns
  • Week 2: Review difficult patterns from first week
  • Week 4: Comprehensive review

Result: Mastered over 100 algorithm patterns in 3 months and passed coding tests.

Effects and Benefits​

Long-term Memory Formation​

Rather than short-term memorization, information converts to long-term memory, remaining accessible years later. The true goal of learning isn't passing exams but gaining knowledge for lifelong use.

Learning Time Efficiency​

Much more efficient than random repetition. Research shows Spaced Repetition is 50-200% more effective than regular repetitive learning. You can remember more for longer with the same time investment.

Reduced Cognitive Load​

No need to review everything daily. Only review what's due today, reducing mental burden. Apps make it even more convenient with automatic management.

Improved Confidence​

Experiencing actual knowledge accumulation through systematic review builds confidence in learning. The anxiety of "what if I forget again" disappears.

Wide Applicability​

Applicable to almost any field requiring memorization: language learning, medical terminology, historical dates, formulas, code syntax, etc.

Metacognition Development​

You can clearly identify what you know and don't know. Evaluating your understanding with each card review provides objective awareness of your learning state.

Precautions​

Avoid Rote Memorization Without Understanding​

Spaced Repetition is a memorization tool, not a substitute for understanding. Use it to memorize after understanding concepts first. Memorizing words without meaning leads to quick forgetting.

Card Quality Matters​

Ambiguous or information-overloaded cards are less effective. Use "Can I answer this in 10 seconds?" as your card creation criterion. One card should contain one fact.

Maintain Consistency​

Skipping a day or two causes cards to pile up and become burdensome. Consistency matters—even 10-20 minutes daily. Include it in routines like commute times or before/after meals.

Beware of Creating Too Many Cards​

Starting with too many cards makes maintenance difficult. About 10-20 new cards daily is appropriate. Gradually increase.

Eliminate Perfectionism​

You don't need to make cards for everything. Select only core information that truly needs long-term retention.

Manage App Dependency​

Apps are just tools. Actually learning and reviewing matters more than perfect app setup. Don't obsess over tools.

FAQ​

Q: Which app should I use? A: Options include Anki (free, powerful customization), Quizlet (easy to use, sharing features), RemNote (integrated with note-taking), SuperMemo (original algorithm). Beginners should try Quizlet or Anki. Regardless of choice, consistent use matters most.

Q: How should I create cards? A: Keep them simple and clear. Specific questions, short answers. "When did the French Revolution occur?" (1789) / "What is oxygen's chemical symbol?" (O) / "What's Python's list reversal method?" (reverse()). Adding images enhances effectiveness.

Q: How much time should I invest daily? A: Initially 30-60 minutes for creating and learning new cards, then 10-20 minutes daily during maintenance phase. Using commute time or spare moments reduces burden.

Q: Can I create cards for already learned content? A: Absolutely. It's very effective for consolidating known content into long-term memory. Create cards from important parts while reviewing textbooks or lecture notes.

Q: If I don't review for months, do I start from scratch? A: No. The app remembers your last review point and starts based on previous progress even after long breaks. However, expect many forgotten cards, so restart with patience.

Q: Can this be used for children's education? A: Yes, perfectly suitable for elementary school age and above. Multiplication tables, English words, historical dates can be learned enjoyably. A game-like approach keeps children interested. Creating cards together with parents is even more effective.