Spaced Repetition

Spaced repetition is a learning technique that reviews information at increasing intervals, timed to when you’re about to forget it. Cortex automatically generates flashcards from your notes and schedules them using an adaptive algorithm.

The Forgetting Curve

In 1885, Hermann Ebbinghaus discovered that memory decays exponentially over time. Without review, you forget:

• 50% within 1 hour
• 70% within 24 hours
• 90% within 1 week

Spaced repetition fights this by reviewing at optimal intervals:

Day 1    Day 3    Day 7    Day 14    Day 30    Day 90
  ✓        ✓        ✓        ✓         ✓         ✓
  └────────┴────────┴────────┴─────────┴─────────┘
              Intervals grow exponentially

Each successful review doubles (approximately) the interval until the next review.

How Cortex Generates Flashcards

When you create a note with importance ≥ 0.5, Cortex can generate flashcards:

1. Extract key claims from the note content
2. Generate question-answer pairs using the note’s declarative title
3. Schedule the first review for the next day
4. Adapt intervals based on your responses

Example

Note: “Active recall is more effective than passive review”

Generated flashcard:

• Q: What learning technique is more effective than passive review (re-reading, highlighting)?
• A: Active recall — testing yourself on the material, even before you feel ready.

Review Flow

When a flashcard is due:

1. You see the question
2. You attempt to recall the answer
3. You reveal the answer and rate your recall:
   • Again — Forgot completely. Reset interval to 1 day.
   • Hard — Partially remembered. Interval × 1.2
   • Good — Remembered correctly. Interval × 2.0
   • Easy — Instant recall. Interval × 2.5

Importance and Review Priority

Not all notes are equal. The importance score affects review scheduling:

• High importance (0.8+): Reviewed more frequently, shorter initial intervals
• Medium importance (0.5–0.7): Standard schedule
• Low importance (< 0.5): No automatic flashcard generation

Integration with Knowledge Graph

Flashcards aren’t isolated — they connect back to your knowledge graph:

• Each flashcard links to its source note
• Reviewing a flashcard reinforces the note’s position in your memory
• Notes that are frequently reviewed gain “memory strength” that boosts their recall ranking
• Related notes are sometimes shown as context during review