Cognitive Scaffold

Preparing your thinking workspace

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MENTAL MODEL · M4029

Half-Life of Knowledge

Half-Life of Knowledge
StructureHigh supportLogic
Included
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Updated 2026-08-08

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INTRODUCTION

English translation pending.

CORE DEFINITION

A concept popularized by the economist Fritz Machlup and later adopted by researchers studying technical change and by the learning and development field. It measures the interval in which roughly half of a field's working knowledge is superseded. The half-life varies enormously by domain: fast-moving applied fields such as software frameworks may turn over in two to three years, while mathematics, logic, and durable aspects of human behavior change on a scale of decades or centuries. The figure is a planning heuristic rather than a precise constant, and it differs even between sub-specialties of one field.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

- Content sorting: classify what you are learning as fast-decaying or slow-decaying before investing time. - Portfolio weighting: put the bulk of your effort into slow-decaying fundamentals. - Refresh scheduling: adopt fast-decaying knowledge just in time rather than studying it deeply in advance.

anchor

Anchor fast decisions

Knowledge decays because the environment that validated it changes: tools are replaced, versions turn over, and empirical findings are revised. Fundamentals decay slowly because they encode constraints that rarely move, such as logic, mathematics, and human incentives. Effort spent on fast-decaying content produces returns that expire on the field's schedule rather than yours, so a portfolio concentrated there requires constant reinvestment merely to hold position.

MINIMUM ACTION

In progress 0/1

Practice this model in one real situation:

Check to track your progress (stored locally)
Learning progress0%
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Source support: Explicit

  • link
    en.wikipedia.orghttps://en.wikipedia.org/wiki/Half-life_of_knowledgeZH · Explicit
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