---
type: permanent
status: mature
created: "2026-01-11"
description: "Distributing review over increasing intervals exploits the spacing effect for long-term retention"
tags:
  - memory
  - study-techniques
  - evidence-based
---

# Spaced Repetition

Spaced repetition is a learning technique where review sessions are distributed over increasing intervals of time. Instead of cramming all study into one session (massed practice), material is revisited at strategically timed gaps.

## Core Mechanism

The technique exploits the [[Spacing Effect]] -- the finding that memory is stronger when study is spread out over time. Each retrieval attempt strengthens the memory trace, and the act of recalling is itself a form of [[Active Recall]].

## How It Works

1. Study new material
2. Review after a short delay (e.g., 1 day)
3. If recalled successfully, increase the interval (e.g., 3 days, then 7, then 21)
4. If recall fails, reset to a shorter interval

Algorithms like SM-2 (used in [[Anki]]) automate this scheduling. The key insight is that you should review *just before* you're about to forget -- the point of maximum [[Desirable Difficulties]].

## Relationship to Other Concepts

- Built on the [[Spacing Effect]] discovered by Ebbinghaus
- Each review session employs [[Active Recall]] rather than passive re-reading
- [[Memory Consolidation]] during sleep between sessions strengthens traces
- Effective spaced repetition requires [[Metacognition]] to judge when material is truly learned

## Evidence

Hundreds of studies support spaced repetition. Cepeda et al. (2006) meta-analysis showed spacing effects across all tested conditions. The technique is one of the most robust findings in cognitive psychology.

#study-techniques #memory
