Cognitive Scaffold

Preparing your thinking workspace

arrow_back_ios_new
MENTAL MODEL · M4134

Fencepost Error

Fencepost Error
StructureHigh supportLogic
Included
account_tree

Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

If you want to build a 100-meter fence and place a post every 10 meters, you need 11 posts, not 10. This is the 'off-by-one error'.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

Boundary calculation. When doing project planning, budgeting, or scheduling, always be wary of that '+1' or '-1' boundary. The start and end nodes are often the overlooked cost centers.

anchor

Anchor fast decisions

When dividing an interval into segments, errors often occur because the number of 'segments' and the number of 'interval points (fence posts)' differ by one. n segments of fence have n+1 posts, and n intervals cover n+1 endpoints.

MINIMUM ACTION

In progress 0/3

Practice this model in one real situation:

Check to track your progress (stored locally)
Learning progress0%
account_treeGenealogyexpand_more
menu_bookReferencesexpand_more

Source support: Explicit

  • link
    zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E5%B7%AE%E4%B8%80%E9%94%99%E8%AF%AFZH · Explicit
    verified

RELATED MODELS

Related model

Ugly Duckling Theorem

Counting all extensional properties equally over a finite set gives different object pairs the same number of shared properties; useful similarity requires selecting or weighting features.

arrow_forwardRelated model

False Equivalence

An informal fallacy that treats limited similarities as establishing equivalence while ignoring differences relevant to the conclusion.

arrow_forwardRelated model

Inferential Distance

How many steps of logical reasoning you must go through to get from what the audience already knows to the conclusion you want to convey.

arrow_forward