Composition Fallacy is what's true of the parts is assumed true of the whole. It sits in the Cognition dimension (COG) of the Human Behavior Taxonomy™ as element HBT-COG-0169, within the Definition Fallacy family. The core principle: what's true of the parts is assumed true of the whole. In incentive terms, it matters because it changes the payoff people perceive before they choose — which means it can be designed for, or exploited.
Scientific Definition
What's true of the parts is assumed true of the whole.
Plain-English Definition
What's true of the parts is assumed true of the whole.
Feynman Explanation
Each ingredient is great. The dish is poison.
Core Principle
What's true of the parts is assumed true of the whole.
Mechanisms
What's true of the parts is assumed true of the whole.
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Inputs (Triggers)
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Outputs (Behaviors)
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Behavioral Signature
Each ingredient is great. The dish is poison.
Examples
- Every team is high-performing; the company still misses its number.
- Aggregate-level dysfunction missed because the parts are 'fine.'
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Original analysis from The Incentives Lab — how this element behaves inside real payoff structures.
Why this element matters to incentive design
When this element shows up in a diagnostic, the instinct is to train people out of it. Training rarely moves it. The mechanism underneath it is straightforward: what's true of the parts is assumed true of the whole. You can recognize it in the field by its signature: each ingredient is great. The dish is poison. Every element in the Cognition dimension changes the perceived payoff of an action before the action happens, which is exactly where incentive design has leverage.
How it gets exploited
Left undesigned, aggregate-level dysfunction missed because the parts are 'fine.'. It is amplified whenever aggregate-level dysfunction missed because the parts are 'fine.'. Inside organizations that shows up as aggregate-level dysfunction missed because the parts are 'fine.'. The pattern is the same one Goodhart's Law describes: the measurable proxy attracts the effort, and the purpose behind it quietly loses funding.
How the Lab designs around it
The redesign move is to make the desired behavior observable, remove whatever currently pays for its opposite, and attach the reward to the behavior rather than to the noisy outcome downstream of it. Measure the behavior, not the sentiment. A survey will tell you how people feel about this; only observed action tells you whether it changed.
Famous Experiments
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Design Principles
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Measurement Approaches
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Evidence
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The Perverse Incentive Lens™
How this behavior is exploited — and how to redesign around it.
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Interactive Mini Network
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Knowledge Graph Neighbors
Auto-linked to the rest of the Human Behavior Taxonomy by family, domain, dimension, and shared keywords.
Assuming the conclusion in the premise.
The conclusion is hidden inside the premise.
Because there's no sharp line, no distinction exists.
Quietly redefining a term mid-argument.
What's true of the whole is assumed true of the parts.
Constraining the option set to bias the decision.
Insisting on a word's original meaning over its current one.
Treating two things as comparable when they're not.
Assuming the truth must lie between two extremes.
Deriving 'is' from 'ought.'
Changing success criteria whenever the prior criteria are met.
Deriving 'ought' from 'is.'
Where Composition Fallacy is cited in the corpus
Essays, field guides, and diagnostics from The Incentives Lab that apply this element.
- EssayGoodhart's Law in the Real World
How measurable proxies capture judgment.
- EssayThe Perverse Incentives Hiding in Your KPIs
Cognitive shortcuts turned into scorecards.
- ReferenceThe incentive glossary
Definitions for every mental model, bias, and fallacy in the corpus.
- CourseIncentives 101
The free ten-part primer on reading a payoff structure.
- ReferenceThe Periodic Table of Human Behavior
The full 1,267-element map this page belongs to.
Questions about Composition Fallacy
- What is Composition Fallacy?
- Composition Fallacy is what's true of the parts is assumed true of the whole. It sits in the Cognition dimension (COG) of the Human Behavior Taxonomy™ as element HBT-COG-0169, within the Definition Fallacy family. The core principle: what's true of the parts is assumed true of the whole. In incentive terms, it matters because it changes the payoff people perceive before they choose — which means it can be designed for, or exploited.
- What is an example of Composition Fallacy?
- Aggregate-level dysfunction missed because the parts are 'fine.' The Incentives Lab catalogs everyday, organizational, and historical instances of this element on its Human Behavior Taxonomy™ page (HBT-COG-0169).
- How is Composition Fallacy exploited?
- Aggregate-level dysfunction missed because the parts are 'fine.'
- How do you design around Composition Fallacy?
- Name the behavior you want in observable terms, remove what currently pays for the opposite, attach the reward to the behavior rather than a lagging proxy, and publish how you will detect gaming.
- Which behavioral dimension does Composition Fallacy belong to?
- Composition Fallacy is classified in the Cognition dimension (COG) of the Human Behavior Taxonomy™, family "Definition Fallacy", class "Logical Fallacy". Its permanent identifier is HBT-COG-0169 and its evidence grade is B.