Spaced Repetition Explained

Spaced Repetition System

Spaced repetition is a scientifically-proven learning technique that optimizes review timing to maximize long-term retention. SubLearn's algorithm ensures you review vocabulary at the perfect moment for optimal memory formation.

What is Spaced Repetition?

Instead of cramming, spaced repetition schedules reviews based on how well you know each word:

New words: Reviewed frequently
Familiar words: Reviewed less often
Mastered words: Reviewed infrequently to prevent forgetting

The intervals between reviews grow exponentially as you demonstrate mastery.

The Forgetting Curve

Research shows we forget information over time unless we review it:

1 hour after learning: 50% forgotten
1 day later: 70% forgotten
1 week later: 90% forgotten

Spaced repetition intervenes just before you'd forget, strengthening the memory trace each time.

🧠 Pro Tip

Trust the algorithm! It might seem like you're not reviewing words often enough, but that's the point. Struggling slightly during recall (the "desirable difficulty") creates stronger memories than easy, frequent repetition.

How SubLearn's Algorithm Works

Initial Learning

First Exposure: You encounter a new word
First Review: 10 minutes later
Second Review: 1 day later
Third Review: 3 days later

Interval Progression

After successful reviews, intervals grow:

7 days
14 days
30 days
60 days
120 days
6 months
1 year

Dynamic Adjustments

The algorithm adapts to your performance:

Correct (Easy): Interval multiplied by 2.5
Correct (Good): Interval multiplied by 2.0
Correct (Hard): Interval multiplied by 1.2
Incorrect: Reset to 1 day

Review Scheduling

Due Cards

Your dashboard shows how many cards are due:

Overdue: Should have been reviewed already (red)
Due Today: Scheduled for review today (yellow)
Upcoming: Due in next few days (green)

Daily Review Limit

Prevent overwhelming review sessions:

Default: 100 reviews per day
Customizable in settings (20-500)
New cards also count toward limit
Unlimited option (Premium)

Review Order

Choose how cards are presented:

Optimal: Algorithm determines best order
Overdue First: Tackle oldest cards first
Random: Shuffle for variety
Difficulty: Hardest or easiest first

Card Ratings

After seeing a card's answer, rate your recall:

Again (1)

Didn't remember the word at all
Resets interval to 1 day
Card marked as "difficult"
Will appear more frequently

Hard (2)

Struggled to remember but eventually got it
Minimal interval increase (1.2x)
Ensures more practice before long gaps

Good (3)

Remembered correctly with normal effort
Standard interval increase (2.0x)
Most common rating

Easy (4)

Instant, effortless recall
Large interval increase (2.5x)
Use sparingly - card should feel trivial

Benefits of Spaced Repetition

Efficient Learning

Learn more with less total study time
Focus on words you're about to forget
Skip unnecessary reviews of well-known words

Long-Term Retention

Moves information to long-term memory
Prevents the "learned it yesterday, forgot it today" problem
Builds durable vocabulary knowledge

Reduced Overwhelm

Manageable daily review loads
No need to study entire vocabulary list each time
Feels achievable and sustainable

Card States

New

Never reviewed before
Waiting to be introduced
Limited by "new cards per day" setting

Learning

In initial rapid review phase
Intervals under 1 week
Requires more frequent practice

Review

In long-term spaced repetition cycle
Intervals 7+ days
Considered "learned"

Mastered

Consistently rated "Easy" or "Good"
Intervals 60+ days
High confidence level
Occasional review maintains retention

Lapsed

Previously learned but forgotten
Rated "Again" after long interval
Returns to learning phase
Relearned faster than first time

Optimizing Your Reviews

Daily Consistency

Review every day, even if just 10 cards
Better than marathon sessions once a week
Keeps the algorithm accurate

Honest Ratings

Don't mark cards "Easy" if you struggled
Accurate ratings = better scheduling
Long-term benefits outweigh short-term XP gains

Timing

Review when mentally fresh (morning often best)
Avoid late-night reviews if tired
Quality > quantity

Advanced Settings (Premium)

Custom Intervals

Modify the interval multipliers
Create aggressive or conservative schedules
Different settings per language

Algorithm Variants

SM-2: Classic spaced repetition (default)
SM-2+: Enhanced with SubLearn adjustments
Aggressive: Longer intervals, higher difficulty
Conservative: Shorter intervals, more reviews

Review Forecasting

See projected reviews for next 30 days
Plan around busy periods
Adjust new card rate to manage future load

Statistics & Analytics

Track how spaced repetition is working:

Retention rate over time
Average interval by card
Most difficult words
Review accuracy trends
Time to mastery predictions