---
type: permanent
status: mature
created: "2026-01-12"
description: "Distributing study sessions over time produces stronger memories than cramming — Ebbinghaus's key finding"
tags:
  - memory
  - learning-principles
  - evidence-based
---

# Spacing Effect

The spacing effect is the robust finding that information is better remembered when study sessions are spaced apart in time rather than massed together. Discovered by Hermann Ebbinghaus in 1885, it remains one of the most replicated results in cognitive psychology.

## Mechanism

Several theories explain the spacing effect:

- **Encoding variability**: Spaced sessions occur in different contexts, creating richer retrieval cues (see [[Encoding Specificity]])
- **Retrieval effort**: Longer gaps require more effort to retrieve, and this effort strengthens memory -- a form of [[Desirable Difficulties]]
- **Consolidation**: Time between sessions allows [[Memory Consolidation]], particularly during sleep

## Applications

- [[Spaced Repetition]] systems like [[Anki]] directly implement the spacing effect
- Curriculum design should distribute practice over weeks rather than cramming into single sessions
- Language learning benefits enormously from spaced vocabulary review

## Key Findings

- The optimal spacing interval depends on when you need to remember (the "lag effect")
- For a test in one week, study sessions 1-2 days apart are ideal
- For retention over months, sessions spaced weeks apart are better

## Connections

- Foundational principle behind [[Spaced Repetition]]
- [[Memory Consolidation]] during inter-study intervals strengthens the effect
- [[Desirable Difficulties]] framework explains why spacing works despite feeling harder
- Contrasts with [[Interleaving]] which varies *content* rather than *time*

#memory #learning-principles
