Gerald Ajam

Library / Glossary

The field guides glossary

640 names for the ways thinking goes wrong — in one mind, in a group, in an exchange — each with its one-line definition from the field guide it belongs to.

The library

What each entry carries

  1. The name, as the field guide gives it.
  2. A brief definition: the one line the entry opens with.
  3. The family it was filed under, and the guide, which opens at the entry.

This is Appendix A of each of the field guides, the three brought into one list: the cognitive bias field guide, the collective fallacies field guide, the faulty arguments field guide. A name that two guides share appears once for each, because each treats it differently.

EntryBrief definitionFamilyGuide
A
Abilene paradox

A group can take a course of action that every member privately opposes, because each mistakes the silence of the others for agreement.

Agreement without beliefFamily 01 · Law02Collective fallaciesslide 11 (opens in a new tab)
Absent-mindedness

Lapses that come from divided attention at the moment of encoding or of acting, not from lost memories.

Memory: encoding and retentionFamily 0301Cognitive biasslide 54 (opens in a new tab)
The absurd counterexample method

Construct an argument of the same form whose conclusion is plainly false.

Moves that workFamily 19 · Repair03Faulty argumentsslide 185 (opens in a new tab)
Abusive analogy

The arguer is compared to something contemptible, and the comparison is offered as though it were an argument.

Attacking the arguerFamily 01 · Procedural03Faulty argumentsslide 21 (opens in a new tab)
Abusive supervision

Subordinates perceive a sustained pattern of hostile verbal and non-verbal conduct from their supervisor, excluding physical contact.

Power & its misuseFamily 18 · Replicated02Collective fallaciesslide 250 (opens in a new tab)
Accent

Meaning is changed by where the stress falls, or by which part of a passage is reproduced, while every word attributed to the speaker is one he said.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 61 (opens in a new tab)
Accident

A sound general rule is applied to a case that lacks the feature the rule was made for.

GeneralisationFamily 10 · Presumptive03Faulty argumentsslide 106 (opens in a new tab)
Accidental adversaries

Two parties who gain from cooperating each take a local action that solves their own problem by obstructing the other, and the partnership decays without anyone intending it.

Systems that push backFamily 11 · Model02Collective fallaciesslide 162 (opens in a new tab)
Accountability diffusion in AI

Responsibility spread so widely across an AI project that nobody feels answerable for its decisions.

AI, automation & delegationFamily 1701Cognitive biasslide 255 (opens in a new tab)
The accountability gap

An automated decision passes through so many hands that no one of them can be held answerable for its outcome, and the system itself cannot be.

Delegated judgementFamily 14 · Model02Collective fallaciesslide 208 (opens in a new tab)
Accountability sinks

A structure that breaks the link between a decision and anyone who can be asked about it, so complaints arrive nowhere.

Effort & responsibilityFamily 02 · Model02Collective fallaciesslide 38 (opens in a new tab)
Action bias

Acting by default rather than waiting, because visible effort feels safer than doing nothing.

Action, commitment & inertiaFamily 1501Cognitive biasslide 233 (opens in a new tab)
Actor–observer bias

We explain our own behaviour by the situation and the behaviour of others by character.

Judging other peopleFamily 0901Cognitive biasslide 163 (opens in a new tab)
Ad hoc rescue

A refuted claim is preserved by adding an assumption whose only support is that it saves the claim.

Burden and ignoranceFamily 15 · Procedural03Faulty argumentsslide 150 (opens in a new tab)
Ad hominem, abusive

The arguer is attacked in place of the argument, on grounds that would not bear on the claim even if every word of the attack were true.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 10 (opens in a new tab)
Ad hominem, bias

The arguer is said to be so committed to a side that nothing he says on the subject can count.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 12 (opens in a new tab)
Ad hominem, circumstantial

The arguer’s position, interest or circumstances are offered as the reason his argument fails.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 11 (opens in a new tab)
Adverse selection

When one side knows more about quality or risk than the other, the better-than-average side withdraws and the market can unravel to nothing.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 90 (opens in a new tab)
Affect heuristic

We read our feeling about a thing as information about its risks and benefits.

Heuristics & mental economyFamily 0201Cognitive biasslide 27 (opens in a new tab)
Affirming a disjunct

One member of an either-or is found to hold and the other is denied on that ground alone.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 80 (opens in a new tab)
Affirming the consequent

The consequent of a conditional is found to hold and the antecedent is inferred from it.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 78 (opens in a new tab)
The ageing safety case

A safety argument is true of the system as it was when the argument was written, and quietly becomes false as the system, its staff and its demands change around it.

Drift & accidentFamily 13 · Maxim02Collective fallaciesslide 199 (opens in a new tab)
Agenda setting

Media coverage transfers salience rather than opinion: the issues given most attention become the issues the public names as most important.

Manufactured consensusFamily 20 · Replicated02Collective fallaciesslide 278 (opens in a new tab)
AI literacy gap

The shortfall between understanding how AI systems work and how confidently people use them.

AI, automation & delegationFamily 1701Cognitive biasslide 252 (opens in a new tab)
Algorithm appreciation

Lay judges often weight advice more heavily when it is labelled as coming from an algorithm than from a person, but the preference reverses by task and fades among experts.

Delegated judgementFamily 14 · Disputed02Collective fallaciesslide 207 (opens in a new tab)
Algorithm aversion

People abandon a statistical forecast after seeing it err, even when it is still more accurate than the human judgement they return to.

Delegated judgementFamily 14 · Replicated02Collective fallaciesslide 206 (opens in a new tab)
Algorithmic bias

Systematic, repeatable unfairness produced by a system and its data rather than by a mind.

AI, automation & delegationFamily 1701Cognitive biasslide 256 (opens in a new tab)
All or nothing

A matter of degree is argued as though it admitted only the two end states.

Framing the choiceFamily 14 · Linguistic03Faulty argumentsslide 142 (opens in a new tab)
Ambiguity effect

Avoiding options whose probabilities are unknown, in favour of options whose odds are stated.

Risk, loss & regretFamily 1301Cognitive biasslide 212 (opens in a new tab)
Amphiboly

The ambiguity sits in the grammar rather than in any word, so one sentence yields two readings and the argument quietly takes the one it needs.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 60 (opens in a new tab)
The analogical fallacy

An analogy drawn to make one point is carried on and made to yield conclusions it was never built to support.

Analogy and comparisonFamily 13 · Presumptive03Faulty argumentsslide 132 (opens in a new tab)
Anchoring bias

The first number we are given pulls every later judgement towards it, even when it is irrelevant.

Framing & choice architectureFamily 1101Cognitive biasslide 183 (opens in a new tab)
Anecdotal evidence

A single vivid case is treated as evidence of a general effect.

Argument & inferenceFamily 0701Cognitive biasslide 113 (opens in a new tab)
Anecdotal evidence

A single vivid case is offered where a rate is required.

GeneralisationFamily 10 · Epistemic03Faulty argumentsslide 105 (opens in a new tab)
Anthropomorphism

We attribute minds, intentions and feelings to things that have none.

AI, automation & delegationFamily 1701Cognitive biasslide 257 (opens in a new tab)
Appeal to anonymous authority

Authority is invoked without being named, so that it cannot be checked.

Deference and its abuseFamily 02 · Epistemic03Faulty argumentsslide 26 (opens in a new tab)
Appeal to common practice

A practice is defended on the ground that it is what everybody does.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 28 (opens in a new tab)
Appeal to consequences

A proposition is affirmed or denied on the strength of what would follow from accepting it.

Pressure instead of proofFamily 04 · Epistemic03Faulty argumentsslide 53 (opens in a new tab)
Appeal to fear

A frightening outcome the speaker does not control is described, and the description is offered in place of the case.

Pressure instead of proofFamily 04 · Presumptive03Faulty argumentsslide 50 (opens in a new tab)
Appeal to flattery and to spite

The hearer is offered a compliment, or an enemy’s discomfort, as his reason for agreeing.

Pressure instead of proofFamily 04 · Procedural03Faulty argumentsslide 52 (opens in a new tab)
Appeal to force

A penalty is attached to disagreement, and the penalty is offered in the place a reason should occupy.

Pressure instead of proofFamily 04 · Procedural03Faulty argumentsslide 49 (opens in a new tab)
Appeal to inappropriate authority

An expert opinion is cited where the expert is not an authority on the question, or where the question is not one authority can settle.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 24 (opens in a new tab)
Appeal to motive

An argument is dismissed by supplying a motive for making it.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 20 (opens in a new tab)
Appeal to nature

Something is held to be good because it is natural, or bad because it is not.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 31 (opens in a new tab)
Appeal to novelty

Treating an idea as better because it is new.

Argument & inferenceFamily 0701Cognitive biasslide 114 (opens in a new tab)
Appeal to novelty

A thing is recommended by its newness.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 30 (opens in a new tab)
Appeal to pity

Distress is presented where a ground was owed, so that refusing the claim becomes a refusal of the sufferer.

Pressure instead of proofFamily 04 · Presumptive03Faulty argumentsslide 51 (opens in a new tab)
Appeal to probability

Treating something likely, or merely possible, as though it were certain.

Argument & inferenceFamily 0701Cognitive biasslide 115 (opens in a new tab)
Appeal to self-interest

A benefit to the hearer is supplied in place of a reason for the claim.

Pressure instead of proofFamily 04 · Procedural03Faulty argumentsslide 55 (opens in a new tab)
Appeal to the people

A claim is supported by the number of people who accept it.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 27 (opens in a new tab)
Appeal to tradition

A practice is defended by its age.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 29 (opens in a new tab)
Appeal to wealth and poverty

A claim is supported by the prosperity of the person making it, or by their lack of it.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 32 (opens in a new tab)
Argument by innuendo

A charge is conveyed without being asserted, so that it can be understood and cannot be answered.

DiversionFamily 03 · Linguistic03Faulty argumentsslide 45 (opens in a new tab)
Argument by repetition

A claim is repeated until familiarity does the work that evidence did not.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 166 (opens in a new tab)
Argument from fallacy

Concluding a claim is false because the argument offered for it was bad.

Argument & inferenceFamily 0701Cognitive biasslide 116 (opens in a new tab)
Argument from fallacy

A conclusion is treated as false because the argument offered for it was bad.

The fallacy charge as a weaponFamily 18 · Formal03Faulty argumentsslide 172 (opens in a new tab)
Argument from ignorance

The absence of evidence for a claim is offered as evidence that it is false, or the absence of evidence against it as evidence that it is true.

Burden and ignoranceFamily 15 · Presumptive03Faulty argumentsslide 145 (opens in a new tab)
Argument from incredulity

The arguer’s inability to imagine how something could be so is offered as a reason for thinking it is not so.

Burden and ignoranceFamily 15 · Epistemic03Faulty argumentsslide 147 (opens in a new tab)
Argument from sign

An observed indicator is taken to establish the condition it usually accompanies.

Analogy and comparisonFamily 13 · Presumptive03Faulty argumentsslide 133 (opens in a new tab)
Arms-race dynamics

Each side arms because the other has, so both spend heavily and neither ends up safer than it began.

Games you are made to playFamily 06 · Model02Collective fallaciesslide 94 (opens in a new tab)
Asch conformity

People will state an answer they can see is wrong when everyone ahead of them has stated it.

Agreement without beliefFamily 01 · Replicated02Collective fallaciesslide 24 (opens in a new tab)
Associative memory illusions

A word never presented is recalled as vividly as the studied words that all point to it.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 64 (opens in a new tab)
Astroturfing

A campaign funded and directed by an interested party is presented as spontaneous public opinion, so that a sponsor’s position appears to be a constituency’s.

Manufactured consensusFamily 20 · Model02Collective fallaciesslide 276 (opens in a new tab)
Attentional bias

Our tendency to focus on some elements of our environment while ignoring others.

Attention & exposureFamily 0101Cognitive biasslide 11 (opens in a new tab)
The audit society

An account of how checking spreads until organisations reshape their work to produce the traces an auditor can verify, and verification of the traces replaces knowledge of performance.

Targets that eat themselvesFamily 04 · Model02Collective fallaciesslide 66 (opens in a new tab)
Authority bias

Treating a claim as more valid because an authority figure made it.

Judging other peopleFamily 0901Cognitive biasslide 149 (opens in a new tab)
Authority gradient

The steeper the perceived power difference in a team, the less likely the junior member is to say what they have seen.

Agreement without beliefFamily 01 · Law02Collective fallaciesslide 23 (opens in a new tab)
Automation bias

Favouring the answers of an automated system even when we can see contradictory evidence.

AI, automation & delegationFamily 1701Cognitive biasslide 251 (opens in a new tab)
Automation complacency

Operators monitoring a highly reliable automated system check it less and less, and so miss the rare occasion when it is wrong.

Delegated judgementFamily 14 · Replicated02Collective fallaciesslide 202 (opens in a new tab)
Automation surprise

The machine does something the operator did not expect, and the operator cannot work out what it is doing, or why, in the time available.

Delegated judgementFamily 14 · Model02Collective fallaciesslide 204 (opens in a new tab)
Availability cascade

A risk gains public credibility through repetition rather than measurement, because each retelling makes it easier to recall and makes doubt more costly to voice.

Norms & what they make trueFamily 16 · Model02Collective fallaciesslide 233 (opens in a new tab)
Availability heuristic

We judge how likely something is by how easily an instance of it comes to mind.

Heuristics & mental economyFamily 0201Cognitive biasslide 26 (opens in a new tab)
B
Backfire effect

The claim that correcting a false belief strengthens it, which has largely failed to replicate.

Belief & evidenceFamily 0601Cognitive biasslide 103 (opens in a new tab)
Bandwagon effect

Adopting a behaviour or belief because many other people have.

Social influence & normsFamily 1001Cognitive biasslide 168 (opens in a new tab)
Barnum effect

We read generic descriptions that would fit almost anyone as precise portraits of ourselves.

Belief & evidenceFamily 0601Cognitive biasslide 100 (opens in a new tab)
Base rate fallacy

Given both a statistical base rate and a specific description, we weight the description and neglect the rate.

Probability & randomnessFamily 0501Cognitive biasslide 78 (opens in a new tab)
Base rate neglect

A test result or a match is turned into a probability about the case without the prevalence of the condition being used.

Numbers as premisesFamily 12 · Epistemic03Faulty argumentsslide 124 (opens in a new tab)
Begging the question

The conclusion is assumed among the premises, so the argument is valid and supplies no reason to accept it.

Assuming what you are provingFamily 08 · Epistemic03Faulty argumentsslide 89 (opens in a new tab)
Belief bias

We judge an argument valid when we agree with its conclusion.

Argument & inferenceFamily 0701Cognitive biasslide 117 (opens in a new tab)
Belief perseverance

A belief outlives the evidence that created it, even after that evidence is withdrawn.

Belief & evidenceFamily 0601Cognitive biasslide 96 (opens in a new tab)
The benchmarking trap

Copying the practices of measured high performers makes organisations more alike without making them better, because the practices were never what produced the performance.

Targets that eat themselvesFamily 04 · Model02Collective fallaciesslide 68 (opens in a new tab)
The benefits realisation gap

The outputs of a project are delivered while the benefits promised in its business case are never measured, never realised, or quietly redefined.

Projects & their promisesFamily 12 · Replicated02Collective fallaciesslide 185 (opens in a new tab)
Benjamin Franklin effect

Doing someone a favour makes us feel more positively toward them.

Social influence & normsFamily 1001Cognitive biasslide 173 (opens in a new tab)
The best-practice cargo cult

Copying the visible practices of a successful organisation imports the form without the conditions that made it work, and the conditions are usually what mattered.

Legitimacy over functionFamily 09 · Maxim02Collective fallaciesslide 132 (opens in a new tab)
Bias blind spot

We recognise bias in other people and not in ourselves, because we judge ourselves from the inside.

Self-assessment & confidenceFamily 0801Cognitive biasslide 136 (opens in a new tab)
Biases in deductive reasoning

Asked what follows logically, people answer from content, word order and familiarity instead.

Argument & inferenceFamily 0701Cognitive biasslide 118 (opens in a new tab)
The big-bang rewrite

Replacing a working system wholesale rather than piece by piece trades a known set of defects for an unknown one, and buys an interval in which nothing ships.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 128 (opens in a new tab)
Bikeshedding

Groups spend their time on trivial items and wave the consequential ones through.

Attention & exposureFamily 0101Cognitive biasslide 14 (opens in a new tab)
Bikeshedding

A committee will spend more time on the item it understands than on the item that matters.

Effort & responsibilityFamily 02 · Law02Collective fallaciesslide 35 (opens in a new tab)
Bizarreness effect

Odd or incongruous material is recalled better than ordinary material, but only under narrow conditions.

Memory: encoding and retentionFamily 0301Cognitive biasslide 38 (opens in a new tab)
Blinding with science

Technical language and apparatus are used to make a claim unchallengeable rather than clearer.

Deference and its abuseFamily 02 · Procedural03Faulty argumentsslide 34 (opens in a new tab)
The bogus dilemma

The two alternatives are exhaustive, and at least one of the consequences attached to them does not follow.

Framing the choiceFamily 14 · Presumptive03Faulty argumentsslide 138 (opens in a new tab)
The boomerang effect in norm messaging

Telling people how they compare with the average moves those already better than average in the wrong direction, unless the message also says which direction is approved.

Norms & what they make trueFamily 16 · Replicated02Collective fallaciesslide 230 (opens in a new tab)
Bootleggers and Baptists

Durable regulation usually needs two coalitions: one that argues for it on moral grounds in public, and one that profits from it quietly.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 140 (opens in a new tab)
Bottom-dollar effect

A purchase that exhausts its budget is enjoyed less than the same purchase made with money to spare.

Money, value & ownershipFamily 1201Cognitive biasslide 201 (opens in a new tab)
Bounded rationality

We satisfice rather than optimise, because our information and computing capacity are limited.

Heuristics & mental economyFamily 0201Cognitive biasslide 25 (opens in a new tab)
Braess’s paradox

Adding a road to a network in which drivers choose their own routes can make every driver slower.

Before you move the fenceFamily 10 · Derived02Collective fallaciesslide 150 (opens in a new tab)
Broken windows

Visible small disorder, left unrepaired, is held to signal that nobody is watching, and so to invite larger disorder.

Drift & accidentFamily 13 · Disputed02Collective fallaciesslide 198 (opens in a new tab)
Brooks’s law

Adding people to a late software project makes it later.

How the work gets shapedFamily 08 · Law02Collective fallaciesslide 117 (opens in a new tab)
The budget-maximising bureau

An agency that is the sole supplier of its output to a sponsor who cannot see its costs can secure a budget well above what the service requires.

Laws of growth & decayFamily 07 · Model02Collective fallaciesslide 113 (opens in a new tab)
Buffer erosion

Safety time held inside individual task estimates is consumed rather than pooled, so a project can run out of protection long before it runs out of work.

Projects & their promisesFamily 12 · Model02Collective fallaciesslide 176 (opens in a new tab)
Bullwhip effect

Variation in end demand is amplified at each step back up a supply chain, so the stage furthest upstream sees swings many times larger than anything the customer did.

Systems that push backFamily 11 · Replicated02Collective fallaciesslide 167 (opens in a new tab)
Bulverism

The arguer explains why you hold your mistaken view before establishing that it is mistaken.

Attacking the arguerFamily 01 · Epistemic03Faulty argumentsslide 19 (opens in a new tab)
Bundling bias

Bought as a bundle, items get used less than the same items bought one at a time.

Money, value & ownershipFamily 1201Cognitive biasslide 202 (opens in a new tab)
Bus factor

The number of people who would have to leave before the work could not be carried on, and a warning that the number is usually smaller than anyone thinks.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 120 (opens in a new tab)
Bye-now effect

Seeing or hearing the word bye is said to activate buy, and to raise willingness to spend.

Framing & choice architectureFamily 1101Cognitive biasslide 188 (opens in a new tab)
Bystander effect

The more people who witness a situation that calls for help, the less likely any one of them is to act.

Effort & responsibilityFamily 02 · Disputed02Collective fallaciesslide 32 (opens in a new tab)
C
Campbell’s law

The more a quantitative indicator is used to make decisions, the more it will be corrupted and the more it will distort the process it was meant to monitor.

Targets that eat themselvesFamily 04 · Law02Collective fallaciesslide 55 (opens in a new tab)
Cargo cult

Copying the visible forms of a successful practice while missing the mechanism that made it work, and expecting the results to follow.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 122 (opens in a new tab)
Cascading failure

When the load carried by a failed element is redistributed to its neighbours, each with a finite margin, a single local failure can propagate until it takes down a system far larger than itself.

Drift & accidentFamily 13 · Derived02Collective fallaciesslide 192 (opens in a new tab)
Cashless effect

We spend more freely when no physical money changes hands.

Money, value & ownershipFamily 1201Cognitive biasslide 200 (opens in a new tab)
Category size bias

We rate an outcome likelier when it belongs to a large category than to a small one.

Probability & randomnessFamily 0501Cognitive biasslide 83 (opens in a new tab)
Causal oversimplification

One contributing cause is named as the cause of an outcome that several conditions jointly produced.

CauseFamily 11 · Presumptive03Faulty argumentsslide 118 (opens in a new tab)
Causal slippery slope

A first step is opposed because it is forecast to set off a chain of consequences ending somewhere unacceptable.

CauseFamily 11 · Presumptive03Faulty argumentsslide 120 (opens in a new tab)
Ceremonial conformity and decoupling

Organisations adopt the structures their environment rewards and then insulate the real work from them, so policy and practice run on separate tracks.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 131 (opens in a new tab)
The change curve

The five stages of grief, borrowed as a schedule for how staff will react to organisational change, despite failing as a description of grief itself.

Projects & their promisesFamily 12 · Disputed02Collective fallaciesslide 184 (opens in a new tab)
Cheerleader effect

A face is rated slightly more attractive when seen in a group than when seen on its own.

Judging other peopleFamily 0901Cognitive biasslide 155 (opens in a new tab)
Cherry-picking

The cases that support the conclusion are reported and the cases that do not are left out.

GeneralisationFamily 10 · Epistemic03Faulty argumentsslide 109 (opens in a new tab)
Chesterton’s fence

Do not remove a rule or a structure until you can say what it was put there to do.

Before you move the fenceFamily 10 · Maxim02Collective fallaciesslide 144 (opens in a new tab)
Chicken and brinkmanship

A contest in which a threat works only if the other side believes you will not back down, so the advantage goes to whoever can visibly destroy their own ability to back down.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 85 (opens in a new tab)
Choice overload

Too many options degrade the decision, or prevent it being made at all.

Heuristics & mental economyFamily 0201Cognitive biasslide 29 (opens in a new tab)
Choice-supportive bias

We remember the option we chose as better than it was, and the ones we rejected as worse.

Belief & evidenceFamily 0601Cognitive biasslide 104 (opens in a new tab)
Chronological snobbery

A view is dismissed because of when it was held rather than because of what is wrong with it.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 18 (opens in a new tab)
Circular reasoning

The conclusion supports a premise which supports the conclusion, around a loop wide enough to be lost.

Assuming what you are provingFamily 08 · Epistemic03Faulty argumentsslide 90 (opens in a new tab)
Clustering illusion

Random data contains streaks and gaps, and we read them as structure.

Probability & randomnessFamily 0501Cognitive biasslide 87 (opens in a new tab)
Cobra effect

A reward offered for reducing something creates a supply of the thing, so the scheme increases what it was meant to suppress.

Targets that eat themselvesFamily 04 · Law02Collective fallaciesslide 60 (opens in a new tab)
Cognitive dissonance

The discomfort of holding conflicting beliefs, and the reasoning we do to make it stop.

Belief & evidenceFamily 0601Cognitive biasslide 97 (opens in a new tab)
Collective action problem

A group of people who all want the same outcome will not act to produce it, because each does better letting the others pay for it.

Effort & responsibilityFamily 02 · Derived02Collective fallaciesslide 33 (opens in a new tab)
Commitment bias

We stay with a course we chose, especially in public, even as the results come in bad.

Action, commitment & inertiaFamily 1501Cognitive biasslide 236 (opens in a new tab)
The common-knowledge problem

Coordinated action often requires not merely that everyone knows a fact, but that everyone knows that everyone knows it, and no exchange of fallible messages can establish that.

Agreement without beliefFamily 01 · Derived02Collective fallaciesslide 16 (opens in a new tab)
Common-mode failure

Redundant components that share a cause fail together, so a reliability figure obtained by multiplying independent failure probabilities can be wrong by orders of magnitude.

Drift & accidentFamily 13 · Derived02Collective fallaciesslide 191 (opens in a new tab)
Compliance and security theatre

Measures that produce the appearance of safety or compliance for an audience while doing little to the risk they are said to address.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 124 (opens in a new tab)
Concealed quantification

A statement about a class is made without saying how much of the class it covers, so that it can be defended as “some” and used as “all”.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 64 (opens in a new tab)
Conceding well

Give up the part of your position that has been defeated, explicitly, and keep arguing for the rest.

Moves that workFamily 19 · Repair03Faulty argumentsslide 187 (opens in a new tab)
Concentrated benefits, diffuse costs

A small group with a large stake each will organise; a large group with a small stake each will not, so policy tilts towards the few even when the many lose more in total.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 93 (opens in a new tab)
Conclusion denying the premises

The conclusion, if accepted, undermines the premises that were used to reach it.

Arguing against yourselfFamily 09 · Formal03Faulty argumentsslide 98 (opens in a new tab)
Confabulation

A false account given sincerely, with no intention to deceive and usually no sense of doubt.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 75 (opens in a new tab)
Confirmation bias

We search, read and remember evidence in ways that shield a hypothesis from rejection.

Belief & evidenceFamily 0601Cognitive biasslide 95 (opens in a new tab)
Congruence bias

We test our favoured hypothesis directly and never run the test that would rule it out.

Belief & evidenceFamily 0601Cognitive biasslide 105 (opens in a new tab)
Conjunction fallacy

A conjunction is judged more probable than one of the things it is a conjunction of.

Probability & randomnessFamily 0501Cognitive biasslide 88 (opens in a new tab)
Conservatism in belief revision

Given new evidence we move our beliefs in the right direction, but by too little.

Belief & evidenceFamily 0601Cognitive biasslide 110 (opens in a new tab)
Consistency bias

We recall past attitudes and behaviour as closer to our present ones than they were.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 65 (opens in a new tab)
Conspiracy cascade

A belief spreads through a closed network by cascade and then seals itself, because the evidence that would refute it is issued by the sources the belief has already disqualified.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 271 (opens in a new tab)
Context effect

Material is easier to retrieve in the setting where it was learned than in a different one.

Attention & exposureFamily 0101Cognitive biasslide 17 (opens in a new tab)
Continued influence effect

Retracted information keeps shaping inferences after the person has accepted the retraction.

Belief & evidenceFamily 0601Cognitive biasslide 109 (opens in a new tab)
The continuum fallacy and line-drawing

A distinction is rejected because no sharp boundary can be drawn between its ends, or a boundary is rejected because any particular placing of it would be arbitrary.

Definition as a weaponFamily 06 · Epistemic03Faulty argumentsslide 75 (opens in a new tab)
Contradictory premises

The premises offered cannot all be true, so they establish the conclusion and its denial equally.

Arguing against yourselfFamily 09 · Formal03Faulty argumentsslide 97 (opens in a new tab)
Contrast effect

A thing looks better or worse depending on what we happened to see immediately before it.

Framing & choice architectureFamily 1101Cognitive biasslide 191 (opens in a new tab)
Converse accident

A general rule is built out of a case that was exceptional in the respect that matters.

GeneralisationFamily 10 · Presumptive03Faulty argumentsslide 107 (opens in a new tab)
Conway’s law

Any organisation that designs a system will produce a design whose structure copies the communication structure of that organisation.

How the work gets shapedFamily 08 · Law02Collective fallaciesslide 115 (opens in a new tab)
Coordination cost

Each person added to a group adds more links than hands, so the cost of keeping everyone aligned grows faster than the group does.

Laws of growth & decayFamily 07 · Derived02Collective fallaciesslide 112 (opens in a new tab)
Coordination neglect

Organisations divide work competently and then fail to put it back together, because division is visible and integration is not.

Effort & responsibilityFamily 02 · Model02Collective fallaciesslide 34 (opens in a new tab)
Countless counterfeits

The sheer number of unreliable reports of something is offered as a reason to think some of them must be reliable.

Burden and ignoranceFamily 15 · Epistemic03Faulty argumentsslide 153 (opens in a new tab)
Court politics

Where one person holds wide discretion, the organisation reorganises itself around access to that person, and proximity becomes the currency the formal structure no longer describes.

Power & its misuseFamily 18 · Model02Collective fallaciesslide 256 (opens in a new tab)
The courtier’s reply

A criticism is refused on the ground that the critic has not read enough of the literature he is criticising.

Attacking the arguerFamily 01 · Procedural03Faulty argumentsslide 22 (opens in a new tab)
Cream-skimming

When performance is judged on outcomes, providers raise the average by selecting the cases most likely to succeed and quietly shedding the rest.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 65 (opens in a new tab)
Credential inflation

As a qualification becomes more common, the level demanded for a given job rises, so more education buys the same position.

Sorting & the ladderFamily 17 · Model02Collective fallaciesslide 247 (opens in a new tab)
The critical question

Every defeasible argument comes with a fixed set of questions it must be able to answer, and asking one is the whole counter-move.

Moves that workFamily 19 · Repair03Faulty argumentsslide 180 (opens in a new tab)
Cross-race effect

Faces from our own racial group are recognised more accurately than faces from other groups.

Judging other peopleFamily 0901Cognitive biasslide 156 (opens in a new tab)
Crowd psychology

The idea that a crowd dissolves individual judgement into a primitive collective mind comes from Le Bon and has no evidential support; systematic study finds crowd action patterned and bounded by shared identity.

Manias & group delusionsFamily 19 · Disputed02Collective fallaciesslide 274 (opens in a new tab)
Cryptomnesia

An idea comes back as our own because we remember the idea but not where we got it.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 73 (opens in a new tab)
Cue-dependent forgetting

Material we cannot recall is often still stored, and fails only because the right cue is missing.

Memory: encoding and retentionFamily 0301Cognitive biasslide 51 (opens in a new tab)
Cum hoc ergo propter hoc

Two things found together are taken to stand in a causal relation on that ground alone.

CauseFamily 11 · Presumptive03Faulty argumentsslide 115 (opens in a new tab)
Curriculum narrowing

Time and attention move to the tested subjects, so the curriculum shrinks to the shape of the accountability measure.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 64 (opens in a new tab)
Curse of knowledge

Once we know something we cannot model a mind that does not, so we explain it badly.

Judging other peopleFamily 0901Cognitive biasslide 157 (opens in a new tab)
The curse of the business book

Companies selected as exemplars by a bestselling management book tend to fall back towards the average soon after publication, leaving the principles drawn from them unsupported.

The story told afterwardsFamily 15 · Law02Collective fallaciesslide 219 (opens in a new tab)
D
Damning the alternatives

A position is established by discrediting the other options on a list the arguer drew up.

Framing the choiceFamily 14 · Epistemic03Faulty argumentsslide 139 (opens in a new tab)
Dark patterns

Interfaces built so that the choice favouring the operator is easy and the choice favouring the user is effortful, hidden or embarrassing.

Manufactured consensusFamily 20 · Replicated02Collective fallaciesslide 281 (opens in a new tab)
Dark-triad leadership

The claim that narcissism, Machiavellianism and psychopathy are concentrated at the top of organisations and account for much of the harm done there, which the measured literature supports far more weakly than the claim is made.

Power & its misuseFamily 18 · Disputed02Collective fallaciesslide 255 (opens in a new tab)
DARVO

A person or body answering an accusation denies the conduct, attacks the credibility of whoever raised it, and reverses the roles so that the accused appears as the injured party and the accuser as the aggressor.

Manufactured consensusFamily 20 · Model02Collective fallaciesslide 286 (opens in a new tab)
Decision fatigue

The quality of our decisions falls as we make more of them.

Heuristics & mental economyFamily 0201Cognitive biasslide 28 (opens in a new tab)
Declinism

Believing things were better before and are getting worse.

Belief & evidenceFamily 0601Cognitive biasslide 102 (opens in a new tab)
Decoy effect

Adding a third, clearly inferior option changes which of the original two we choose.

Framing & choice architectureFamily 1101Cognitive biasslide 184 (opens in a new tab)
Defensive attribution

We assign blame for a mishap in whatever way leaves us least likely to suffer one.

Self-assessment & confidenceFamily 0801Cognitive biasslide 137 (opens in a new tab)
Definist fallacy

A contested term is defined into another term, so that a substantive question is settled by the definition rather than by evidence.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 71 (opens in a new tab)
Definitional retreat

A term is redefined in the middle of an argument so that an objection made against the original meaning no longer applies.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 69 (opens in a new tab)
Deindividuation

Anonymity does not release restraint so much as hand control of behaviour to whatever the local norm happens to be.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 26 (opens in a new tab)
Delay-induced oscillation

A correcting loop that acts on delayed information will overshoot, and if it corrects hard enough relative to the delay the overshoot grows into a standing cycle.

Systems that push backFamily 11 · Derived02Collective fallaciesslide 168 (opens in a new tab)
Delegation creep

Steadily expanding what we let automated systems do, while oversight quietly thins.

AI, automation & delegationFamily 1701Cognitive biasslide 253 (opens in a new tab)
Delmore effect

We set our clearest and most detailed goals for the parts of life that matter least.

Action, commitment & inertiaFamily 1501Cognitive biasslide 241 (opens in a new tab)
Denomination effect

The same sum of money is easier to spend as small units than as one large one.

Framing & choice architectureFamily 1101Cognitive biasslide 192 (opens in a new tab)
Denying the antecedent

The antecedent of a conditional is found not to hold and the consequent is denied on that ground.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 79 (opens in a new tab)
Descriptive and injunctive norms

What most people actually do and what most people approve of are two different norms, and a message that confuses them can push behaviour the wrong way.

Norms & what they make trueFamily 16 · Replicated02Collective fallaciesslide 229 (opens in a new tab)
Deskilling

Work is reorganised so that the knowledge needed to do it moves out of the worker and into procedures, machines or management, leaving a narrower job behind.

Delegated judgementFamily 14 · Disputed02Collective fallaciesslide 209 (opens in a new tab)
Deviancy amplification

The reaction to a behaviour increases the behaviour, because the response isolates the people labelled and makes the label the most available identity they have.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 263 (opens in a new tab)
The devil’s advocate paradox

Dissent that is assigned rather than felt reassures a group without changing its mind.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 21 (opens in a new tab)
Dilbert principle

Poor performers are moved into management because that is where they can do least damage to the work.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 101 (opens in a new tab)
Disposition effect

We sell what has gone up and hold what has gone down.

Money, value & ownershipFamily 1201Cognitive biasslide 203 (opens in a new tab)
Distinction bias

Differences that loom large side by side barely register once we live with the choice.

Framing & choice architectureFamily 1101Cognitive biasslide 185 (opens in a new tab)
Door in the face

A request large enough to be refused makes a smaller follow-up more likely to be granted, because the retreat reads as a concession that ought to be reciprocated.

Manufactured consensusFamily 20 · Replicated02Collective fallaciesslide 283 (opens in a new tab)
Downs–Thomson paradox

Where travellers can switch between driving and public transport, road speeds settle at the speed of the alternative, so widening the road can leave everyone slower.

Before you move the fenceFamily 10 · Derived02Collective fallaciesslide 151 (opens in a new tab)
Drawing the wrong conclusion

Evidence that supports one conclusion is used to announce a different and usually stronger one.

DiversionFamily 03 · Formal03Faulty argumentsslide 47 (opens in a new tab)
Dunbar’s number

A cognitive limit of about 150 is said to cap the number of stable relationships a person can hold, and so the size of any group that runs on relationships alone.

Effort & responsibilityFamily 02 · Disputed02Collective fallaciesslide 36 (opens in a new tab)
Dunning–Kruger effect

Lacking skill in an area also removes the means to see that we lack it.

Self-assessment & confidenceFamily 0801Cognitive biasslide 126 (opens in a new tab)
Duration neglect

How long an experience lasted barely enters our later judgement of how good or bad it was.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 74 (opens in a new tab)
E
Ecological fallacy

An association measured between groups need not hold, and can reverse, for the individuals inside them.

Targets that eat themselvesFamily 04 · Derived02Collective fallaciesslide 71 (opens in a new tab)
The efficiency–thoroughness trade-off

People and organisations continually trade thoroughness for efficiency, and because the trade almost always works, the adjustment that normally produces success is the same one that occasionally produces the failure.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 194 (opens in a new tab)
Effort justification

We rate an outcome more highly for having worked hard to get it.

Money, value & ownershipFamily 1201Cognitive biasslide 205 (opens in a new tab)
Effort withdrawal

The response to a perceived unfairness that neither complains nor leaves, but quietly reduces what is given.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 80 (opens in a new tab)
Egocentric bias

We recall our own contribution more readily than anyone else, and claim a larger share of the result.

Self-assessment & confidenceFamily 0801Cognitive biasslide 138 (opens in a new tab)
Einstellung effect

A solution that has worked before blocks us from seeing a better one that is available.

Problem-solving & expertiseFamily 1601Cognitive biasslide 243 (opens in a new tab)
Empathy gap

Underestimating how much a different mental state — ours or someone else’s — changes behaviour.

Time & the future selfFamily 1401Cognitive biasslide 225 (opens in a new tab)
The emperor’s new clothes

When admitting the obvious would mark a person as incompetent or disloyal, a plainly false claim can be maintained in public by everyone at once.

Agreement without beliefFamily 01 · Maxim02Collective fallaciesslide 15 (opens in a new tab)
The empty-chair problem

The people a decision is about are absent when it is made, so the standing remedy is to seat them, or someone who is accountable to them and can lose the argument on their behalf.

Power & its misuseFamily 18 · Maxim02Collective fallaciesslide 258 (opens in a new tab)
Endowment effect

Owning something raises what we demand to give it up above what we would have paid for it.

Money, value & ownershipFamily 1201Cognitive biasslide 197 (opens in a new tab)
Equivocation

A term keeps its shape across an argument and changes its sense, so that a valid-looking inference joins two claims that are not about the same thing.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 59 (opens in a new tab)
Eroding goals

When performance falls short, the gap can be closed by lowering the goal, and a goal that is allowed to move will move.

Systems that push backFamily 11 · Model02Collective fallaciesslide 160 (opens in a new tab)
The error-reporting paradox

Where reporting is safe, reported error rates rise, so a falling error count is as likely to mean that people have stopped telling you as that the work has become safer.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 45 (opens in a new tab)
Escalation

Two parties each act to restore their position relative to the other, so every move provokes the counter-move that makes it necessary again.

Systems that push backFamily 11 · Model02Collective fallaciesslide 161 (opens in a new tab)
Essentialising

A regularity observed in a group is explained by an inner nature the group members are taken to share.

GeneralisationFamily 10 · Presumptive03Faulty argumentsslide 111 (opens in a new tab)
Etymological fallacy

A word’s origin is offered as evidence of what it now means, or of what the thing it names ought to be.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 72 (opens in a new tab)
Ex post facto statistics

The improbability of an event is calculated after the event has been singled out, and the improbability is offered as evidence.

Numbers as premisesFamily 12 · Epistemic03Faulty argumentsslide 126 (opens in a new tab)
Exclusive premises

A conclusion is drawn from two premises both of which are negative, from which nothing follows.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 84 (opens in a new tab)
Existential fallacy

A conclusion asserting that something exists is drawn from premises that assert only universals.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 87 (opens in a new tab)
Explanation taken as excuse

A causal account of why something happened is answered as though it were a justification of it.

Fact and valueFamily 16 · Linguistic03Faulty argumentsslide 161 (opens in a new tab)
Extrinsic incentive bias

We attribute other people’s motives to external rewards and our own to internal ones.

Judging other peopleFamily 0901Cognitive biasslide 152 (opens in a new tab)
F
Fading affect bias

The unpleasantness attached to a memory fades faster than the pleasantness attached to one.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 66 (opens in a new tab)
The fallacy fork

Fallacies as strictly defined are almost never committed; the moves that are common almost never meet the strict definition.

The fallacy charge as a weaponFamily 18 · Epistemic03Faulty argumentsslide 173 (opens in a new tab)
False consensus effect

Overestimating how far other people share our beliefs, values and behaviours.

Judging other peopleFamily 0901Cognitive biasslide 154 (opens in a new tab)
False consensus in groups

Members of a group over-estimate how many colleagues share their reading of a decision, and score silence as agreement.

Agreement without beliefFamily 01 · Replicated02Collective fallaciesslide 27 (opens in a new tab)
False conversion

A categorical statement is reversed, subject for predicate, where its form does not permit it.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 86 (opens in a new tab)
False dilemma

Two options are presented as the whole field, and a third that was available is not mentioned.

Framing the choiceFamily 14 · Presumptive03Faulty argumentsslide 137 (opens in a new tab)
False equivalence

Two things are placed on a par by a shared feature, where they differ by a wide margin in the respect that matters.

Analogy and comparisonFamily 13 · Epistemic03Faulty argumentsslide 135 (opens in a new tab)
False memory

A whole event that never happened can be remembered, with detail and confidence, as if it had.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 67 (opens in a new tab)
False precision

A figure is given to a sharpness its source cannot support, and the sharpness is what persuades.

Numbers as premisesFamily 12 · Epistemic03Faulty argumentsslide 125 (opens in a new tab)
Faulty analogy

Two cases are treated as alike in the respect at issue on the strength of likeness in some other respect.

Analogy and comparisonFamily 13 · Presumptive03Faulty argumentsslide 131 (opens in a new tab)
Fear, uncertainty and doubt

An incumbent defends its position not by making a case but by raising doubts that make any change look risky, so that the safe course is to do nothing.

Manufactured consensusFamily 20 · Law02Collective fallaciesslide 280 (opens in a new tab)
The fine that became a price

A penalty attached to a behaviour can license it, by converting a moral obligation into a service with a stated price.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 75 (opens in a new tab)
The firehose of falsehood

A propaganda pattern defined by high volume across many channels, rapid repetition, and no commitment either to accuracy or to consistency between its own claims.

Manufactured consensusFamily 20 · Model02Collective fallaciesslide 279 (opens in a new tab)
The firehose of falsehood

High-volume, multi-channel, rapid and inconsistent messaging is used to make the truth unlocatable rather than to establish a claim.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 169 (opens in a new tab)
Fixes that fail

A remedy that relieves the symptom quickly sets in motion a slower consequence that returns the symptom, larger.

Systems that push backFamily 11 · Model02Collective fallaciesslide 156 (opens in a new tab)
Focusing illusion

Whatever we are thinking about seems to matter far more to happiness than it does.

Attention & exposureFamily 0101Cognitive biasslide 21 (opens in a new tab)
Folie à deux

A delusion held by two people in a closed relationship, sustained less by transmission from one mind to the other than by the absence of anyone outside able to contradict it.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 273 (opens in a new tab)
Foot in the door

Agreeing to a small request raises the chance of agreeing to a much larger one later, because the first compliance changes how the person describes themselves.

Manufactured consensusFamily 20 · Replicated02Collective fallaciesslide 282 (opens in a new tab)
Forced ranking

Grading a workforce against a fixed distribution and cutting the bottom band, a practice whose claimed benefits rest largely on simulation rather than measurement.

Motivation & its crowdingFamily 05 · Disputed02Collective fallaciesslide 77 (opens in a new tab)
Founder’s syndrome

The habits and informal authority that let a founder build an organisation become the constraint on it once the organisation outgrows what one person can hold.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 109 (opens in a new tab)
Four terms

A syllogism appears to have three terms and has four, because one word has been used in two senses.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 83 (opens in a new tab)
Framing effect

The same facts become more or less attractive depending on which of their features are highlighted.

Framing & choice architectureFamily 1101Cognitive biasslide 182 (opens in a new tab)
The free speech fallacy

The right to hold a view is offered as a reason to accept it, or as a defence against its being examined.

The fallacy charge as a weaponFamily 18 · Epistemic03Faulty argumentsslide 177 (opens in a new tab)
Free-rider problem

When a benefit cannot be withheld from those who do not pay for it, the rational move is to let someone else pay.

Effort & responsibilityFamily 02 · Derived02Collective fallaciesslide 30 (opens in a new tab)
Frequency illusion

After noticing something for the first time, we see it everywhere and take that for a real increase.

Attention & exposureFamily 0101Cognitive biasslide 18 (opens in a new tab)
Functional fixedness

We cannot see an object as anything other than what it is normally used for.

Problem-solving & expertiseFamily 1601Cognitive biasslide 244 (opens in a new tab)
Fundamental attribution error

Judging others’ behaviour, we overweight their personality and discount the situation they are in.

Judging other peopleFamily 0901Cognitive biasslide 147 (opens in a new tab)
G
The Galileo gambit

Rejection by the established view is offered as evidence that the view is right.

Deference and its abuseFamily 02 · Presumptive03Faulty argumentsslide 33 (opens in a new tab)
Gambler’s fallacy

Believing that the outcome of a random event is influenced by the outcomes that came before it.

Probability & randomnessFamily 0501Cognitive biasslide 80 (opens in a new tab)
The gambler’s fallacy

A run of one outcome in an independent process is offered as a reason to expect the other.

Numbers as premisesFamily 12 · Formal03Faulty argumentsslide 127 (opens in a new tab)
The garbage-can model

Where goals are unclear and attention is scarce, decisions are made by the chance meeting of problems, solutions, participants and occasions rather than by anyone solving anything.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 135 (opens in a new tab)
Gaslighting

A sustained attempt to make a person distrust their own perception and memory, so that their account of events can be discounted — by others, and eventually by themselves.

Manufactured consensusFamily 20 · Model02Collective fallaciesslide 285 (opens in a new tab)
Generation effect

Material we produce ourselves is remembered better than the same material read.

Memory: encoding and retentionFamily 0301Cognitive biasslide 39 (opens in a new tab)
Genetic fallacy

A claim is judged by where it came from rather than by what supports it now.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 17 (opens in a new tab)
The Gish gallop

So many claims are made so quickly that answering any of them costs more time than the audience will give.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 164 (opens in a new tab)
The glass ceiling

Women and minority staff move normally through the lower and middle grades and then meet a barrier at senior level that their qualifications, tenure and performance do not explain.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 242 (opens in a new tab)
The glass cliff

Women and minority candidates are appointed more often to leadership posts that are already in trouble, so their tenure starts with a raised chance of visible failure.

Sorting & the ladderFamily 17 · Disputed02Collective fallaciesslide 243 (opens in a new tab)
Goal displacement

A procedure adopted to achieve an end becomes the end, and is defended even where it no longer serves the purpose.

Laws of growth & decayFamily 07 · Model02Collective fallaciesslide 106 (opens in a new tab)
God of the gaps

A gap in the available explanation is filled with a preferred explanation, on the ground that nothing else currently occupies it.

Burden and ignoranceFamily 15 · Epistemic03Faulty argumentsslide 148 (opens in a new tab)
Golem effect

Low expectations held by a teacher or a supervisor are said to depress the performance of the people they are held about, the mirror image of the Pygmalion claim.

Norms & what they make trueFamily 16 · Disputed02Collective fallaciesslide 225 (opens in a new tab)
Goodhart’s law

A measure that was informative while nobody was trying to move it stops being informative once people are required to move it.

Targets that eat themselvesFamily 04 · Law02Collective fallaciesslide 54 (opens in a new tab)
Google effect

We forget information we know we can look up again.

Memory: encoding and retentionFamily 0301Cognitive biasslide 37 (opens in a new tab)
Group attribution error

We read a group decision as the preference of every member, and one member as the whole group.

Judging other peopleFamily 0901Cognitive biasslide 158 (opens in a new tab)
Group polarisation

A group ends its discussion further out than its members started, and more confident about it.

Social influence & normsFamily 1001Cognitive biasslide 175 (opens in a new tab)
Group polarisation

After discussing an issue with like-minded others, people hold more extreme versions of the views they arrived with.

Agreement without beliefFamily 01 · Replicated02Collective fallaciesslide 18 (opens in a new tab)
Groupthink

A group converges on one view and its members quietly abandon the doubts they came in with.

Social influence & normsFamily 1001Cognitive biasslide 176 (opens in a new tab)
Groupthink

A cohesive group under pressure is said to suppress dissent and converge early on a course of action worse than any member would have chosen alone.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 17 (opens in a new tab)
Growth and underinvestment

Growth loads capacity, service quality falls, demand falls with it, and the fall in demand is read as evidence that the capacity was never needed.

Systems that push backFamily 11 · Model02Collective fallaciesslide 163 (opens in a new tab)
Guilt by association

A claim or a person is discredited by naming somebody disreputable who shares the position.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 15 (opens in a new tab)
H
Halo and horns in appraisal

An overall impression of a person colours every separate judgement made about them, so ratings of distinct qualities move together and carry far less information than their number suggests.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 237 (opens in a new tab)
Halo effect

A positive impression in one area colours our judgement of a person, brand or product in unrelated areas.

Judging other peopleFamily 0901Cognitive biasslide 148 (opens in a new tab)
The halo effect in business research

Knowing that a company performed well leads observers to rate its culture, leadership and strategy highly, so studies asking what made great companies great are measuring the result rather than the cause.

The story told afterwardsFamily 15 · Replicated02Collective fallaciesslide 216 (opens in a new tab)
Hard–easy effect

Confidence exceeds accuracy on hard question sets and falls short of it on easy ones.

Self-assessment & confidenceFamily 0801Cognitive biasslide 127 (opens in a new tab)
Hasty generalisation

A general claim is drawn from a sample too small to have shown anything else.

GeneralisationFamily 10 · Presumptive03Faulty argumentsslide 103 (opens in a new tab)
Hawthorne effect

Behaviour is said to change because it is being observed — a claim named after a study whose own data do not support it.

Projects & their promisesFamily 12 · Disputed02Collective fallaciesslide 180 (opens in a new tab)
Hedging

The wording is chosen in advance to be loose enough that any outcome can afterwards be claimed as the one predicted.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 63 (opens in a new tab)
Heuristics

Rules of thumb that make judgement fast and cheap, and sometimes systematically wrong.

Heuristics & mental economyFamily 0201Cognitive biasslide 24 (opens in a new tab)
Hidden profiles

When the information needed for the best decision is divided among members, groups discuss what they already share and miss the answer.

Agreement without beliefFamily 01 · Replicated02Collective fallaciesslide 20 (opens in a new tab)
High-reliability organisations

A few organisations operate hazardous technologies with far fewer accidents than their risk profile predicts, and the explanation offered is a set of organising practices rather than better technology.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 196 (opens in a new tab)
Hindsight bias

Once we know the outcome, we misremember having expected it.

Self-assessment & confidenceFamily 0801Cognitive biasslide 132 (opens in a new tab)
Hindsight in incident review

Once reviewers know how an episode ended, they cannot recover how uncertain it looked beforehand, and the outcome makes the warning signs seem obvious and the decision negligent.

The story told afterwardsFamily 15 · Replicated02Collective fallaciesslide 213 (opens in a new tab)
HiPPO effect

Where evidence is thin or unwelcome, the question is settled by the most senior person in the room.

Agreement without beliefFamily 01 · Law02Collective fallaciesslide 22 (opens in a new tab)
Hofstadter’s law

It always takes longer than you expect, even when you allow for it taking longer.

Time & the future selfFamily 1401Cognitive biasslide 231 (opens in a new tab)
Hollow man

A position is attributed to an opponent who cannot be shown to exist, and is then refuted.

DiversionFamily 03 · Epistemic03Faulty argumentsslide 40 (opens in a new tab)
Homophily and culture fit

Ties form between similar people far more often than chance allows, so a pipeline built on referral reproduces its own composition, and a criterion called fit turns that pattern into a rule.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 241 (opens in a new tab)
Hot hand fallacy

Believing that someone who has just succeeded is more likely to succeed again.

Probability & randomnessFamily 0501Cognitive biasslide 81 (opens in a new tab)
The human error label

Calling an outcome human error names the last person in the chain and ends the inquiry, turning the thing that needs explaining into the explanation.

The story told afterwardsFamily 15 · Model02Collective fallaciesslide 214 (opens in a new tab)
Humour effect

Humorous material is recalled better than neutral material, largely at the expense of the material around it.

Memory: encoding and retentionFamily 0301Cognitive biasslide 40 (opens in a new tab)
Hyperbolic discounting

We choose immediate rewards over later ones, even when the immediate reward is smaller.

Time & the future selfFamily 1401Cognitive biasslide 222 (opens in a new tab)
I
Identifiable victim effect

We feel more, and give more, for one named person than for a large anonymous group.

Attention & exposureFamily 0101Cognitive biasslide 13 (opens in a new tab)
If by whiskey

Both sides of a question are answered with equal warmth, each under a different sense of the key word, so that a position appears to have been taken and none has.

AmbiguityFamily 05 · Procedural03Faulty argumentsslide 65 (opens in a new tab)
Ignoratio elenchi

A conclusion is established soundly, and it is not the conclusion that was owed.

DiversionFamily 03 · Formal03Faulty argumentsslide 41 (opens in a new tab)
Ignoring a common cause

A correlation produced by a third factor acting on both variables is reported as a link between them.

CauseFamily 11 · Presumptive03Faulty argumentsslide 116 (opens in a new tab)
IKEA effect

We value what we built ourselves far above what the same thing is worth to anyone else.

Money, value & ownershipFamily 1201Cognitive biasslide 198 (opens in a new tab)
Illicit contrast

What a statement implies but does not assert is treated as though it had been asserted, so that a contrast the speaker never made is used as a premise.

AmbiguityFamily 05 · Linguistic03Faulty argumentsslide 62 (opens in a new tab)
Illicit major and illicit minor

A term is taken in its whole extent in the conclusion having been taken in part only in the premise.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 82 (opens in a new tab)
Illusion of asymmetric insight

We believe we know others better than they know us, and that our side sees theirs more clearly.

Judging other peopleFamily 0901Cognitive biasslide 159 (opens in a new tab)
Illusion of control

Believing we have more influence over events than we actually do.

Probability & randomnessFamily 0501Cognitive biasslide 86 (opens in a new tab)
Illusion of explanatory depth

We think we understand how things work in detail, until we try to explain one.

Self-assessment & confidenceFamily 0801Cognitive biasslide 128 (opens in a new tab)
Illusion of external agency

We credit whoever handed us an outcome for a satisfaction we produced ourselves.

Self-assessment & confidenceFamily 0801Cognitive biasslide 145 (opens in a new tab)
Illusion of transparency

We overestimate how visible our thoughts and feelings are to other people.

Self-assessment & confidenceFamily 0801Cognitive biasslide 129 (opens in a new tab)
Illusion of validity

Overconfidence in our own interpretations and predictions from a coherent but weak set of data.

Probability & randomnessFamily 0501Cognitive biasslide 85 (opens in a new tab)
Illusions of change

Improvement that did not occur is remembered, because the past self is reconstructed to flatter the present one.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 68 (opens in a new tab)
Illusory correlation

Perceiving a relationship between two variables where none exists.

Probability & randomnessFamily 0501Cognitive biasslide 84 (opens in a new tab)
Illusory superiority

Most people place themselves above the median on most desirable traits, which cannot be true of most people.

Self-assessment & confidenceFamily 0801Cognitive biasslide 139 (opens in a new tab)
Illusory truth effect

Repetition makes a statement feel truer, whether or not it is true.

Belief & evidenceFamily 0601Cognitive biasslide 98 (opens in a new tab)
Impact bias

Overestimating how intense and how long-lasting our emotional reaction to a future event will be.

Time & the future selfFamily 1401Cognitive biasslide 226 (opens in a new tab)
The Implicit Association Test

A reaction-time task whose scores are widely read as a measure of hidden prejudice.

Measurement & research artefactsFamily 1801Cognitive biasslide 265 (opens in a new tab)
Implicit stereotype

Group-linked associations activate automatically, whether or not the person endorses them.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 69 (opens in a new tab)
In-group bias

Giving preferential treatment to people who belong to the same group as us.

Social influence & normsFamily 1001Cognitive biasslide 171 (opens in a new tab)
Incentivization

Attaching a reward to a behaviour, or a penalty to its absence, and expecting behaviour to follow.

Framing & choice architectureFamily 1101Cognitive biasslide 189 (opens in a new tab)
Induced demand

New road capacity is filled by traffic that did not exist before it was built, so congestion returns to close to where it started.

Before you move the fenceFamily 10 · Replicated02Collective fallaciesslide 152 (opens in a new tab)
Inflation of conflict

Disagreement among experts is taken to show that nothing in the field is known.

The fallacy charge as a weaponFamily 18 · Epistemic03Faulty argumentsslide 175 (opens in a new tab)
Information bias

Seeking more information even when no possible answer would change what we do.

Argument & inferenceFamily 0701Cognitive biasslide 119 (opens in a new tab)
Information cascade

When people act in sequence and can see each other’s choices but not their reasons, it becomes rational to ignore your own information, and the group converges on a position resting on the first few signals.

Norms & what they make trueFamily 16 · Derived02Collective fallaciesslide 232 (opens in a new tab)
Information cascades

Each person sensibly defers to those who spoke first, and the group ends up knowing less than its members.

Social influence & normsFamily 1001Cognitive biasslide 177 (opens in a new tab)
Information hoarding as power

Where one person or unit is the only route to something the organisation needs, withholding it is a rational way to hold position.

Voice & silenceFamily 03 · Model02Collective fallaciesslide 51 (opens in a new tab)
Initiative fatigue

Initiatives are added faster than they are retired, so each receives too small a share of attention to change anything.

Projects & their promisesFamily 12 · Law02Collective fallaciesslide 182 (opens in a new tab)
Innovation theatre

Activity that displays innovation — labs, hackathons, accelerators, sprints — while the budgets, procurement rules and decision rights that would let anything new be adopted stay exactly as they were.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 123 (opens in a new tab)
Insensitivity to sample size

How likely a sample result is gets judged without using how large the sample was.

Probability & randomnessFamily 0501Cognitive biasslide 89 (opens in a new tab)
Institutional isomorphism

Organisations in the same field come to resemble one another, not because the shared form works better, but because resemblance secures legitimacy and resources.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 130 (opens in a new tab)
The inverse Conway manoeuvre

Since structure shapes architecture, move the team boundaries first and let the system you want follow.

How the work gets shapedFamily 08 · Maxim02Collective fallaciesslide 116 (opens in a new tab)
Ipse dixit

A claim is offered with no support beyond the fact that it has been asserted.

Deference and its abuseFamily 02 · Epistemic03Faulty argumentsslide 25 (opens in a new tab)
The iron law of megaprojects

Large projects come in over budget, over time and under benefit, at a rate that has not improved across the decades for which records exist.

Projects & their promisesFamily 12 · Replicated02Collective fallaciesslide 170 (opens in a new tab)
Iron law of oligarchy

Any organisation large enough to need full-time officials tends to be run by them, though the evidence makes this a tendency rather than the iron law Michels claimed.

Laws of growth & decayFamily 07 · Disputed02Collective fallaciesslide 104 (opens in a new tab)
The iron triangle

A legislative committee, an agency and an organised interest can close a policy area to outsiders, because each holds something the other two need.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 141 (opens in a new tab)
Ironies of automation

Automating the easy parts of a job leaves the operator the hard parts, less practice at them, and the duty of taking over exactly when things are worst.

Delegated judgementFamily 14 · Model02Collective fallaciesslide 201 (opens in a new tab)
The is-ought gap

An evaluative conclusion is drawn from premises that are wholly descriptive.

Fact and valueFamily 16 · Formal03Faulty argumentsslide 156 (opens in a new tab)
J
The J-curve of change

Performance falls before it rises after a change, because the supports for the old practice go before the new practice is competent.

Projects & their promisesFamily 12 · Model02Collective fallaciesslide 183 (opens in a new tab)
Jevons paradox

Making the use of a resource more efficient can increase the total amount of it consumed, because efficiency makes the service it provides cheaper.

Before you move the fenceFamily 10 · Disputed02Collective fallaciesslide 149 (opens in a new tab)
Just asking questions

An assertion is made in the form of a question, so that it need not be defended.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 168 (opens in a new tab)
Just culture

A reporting system works only when staff know in advance where the line falls between an honest mistake, which will be treated as information, and a reckless act, which will not.

The story told afterwardsFamily 15 · Model02Collective fallaciesslide 215 (opens in a new tab)
Just-world hypothesis

Believing people get what they deserve, so what happened to someone tells us about them.

Belief & evidenceFamily 0601Cognitive biasslide 101 (opens in a new tab)
K
The Kafkatrap

Denial of the charge is counted as evidence for it, so that no answer is available to the accused.

Pressure instead of proofFamily 04 · Epistemic03Faulty argumentsslide 56 (opens in a new tab)
Kettle logic

Several defences are offered together, each adequate alone, which cannot all be true at once.

Arguing against yourselfFamily 09 · Epistemic03Faulty argumentsslide 99 (opens in a new tab)
Kludgeocracy

Because layering a new rule on the old ones is politically cheaper than replacing them, policy accumulates complexity, and the cost of that complexity is paid in citizens’ time.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 137 (opens in a new tab)
L
Labelling theory

An official label applied to a person changes how others treat them and how they come to see themselves, and can produce more of the behaviour it names.

Norms & what they make trueFamily 16 · Model02Collective fallaciesslide 226 (opens in a new tab)
Lag effect

Longer gaps between repeated study of the same material produce better long-term retention.

Memory: encoding and retentionFamily 0301Cognitive biasslide 34 (opens in a new tab)
Law of the instrument

Having mastered a method, we start finding problems everywhere that seem to call for it.

Problem-solving & expertiseFamily 1601Cognitive biasslide 245 (opens in a new tab)
League-table effects

Publishing ranked institutional results changes behaviour inside the institutions, improving the published measure and pulling effort towards whoever sits nearest the line.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 69 (opens in a new tab)
Legibility and high modernism

A state must simplify what it administers into categories it can read, and when the simplification is then imposed as a design, it destroys what made the thing work.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 146 (opens in a new tab)
Leniency, severity and central tendency

Raters differ systematically in where they place people on a scale, some high, some low, some all in the middle, so a rating carries information about the rater as well as about the person rated.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 239 (opens in a new tab)
Less-is-better effect

Judged on its own, the lesser option can beat the option that would beat it in a direct comparison.

Framing & choice architectureFamily 1101Cognitive biasslide 186 (opens in a new tab)
Levelling and sharpening

When we retell a memory we drop the minor details and exaggerate the ones we think matter.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 59 (opens in a new tab)
Levels of processing effect

How material is encoded decides how well it is remembered: meaning beats repetition.

Memory: encoding and retentionFamily 0301Cognitive biasslide 36 (opens in a new tab)
Limits to growth

A reinforcing engine of growth eventually meets a constraint, and pushing the engine harder does nothing but raise the cost of hitting it.

Systems that push backFamily 11 · Model02Collective fallaciesslide 158 (opens in a new tab)
Linguistic relativity

A long-disputed claim that the language we speak shapes what we notice and think.

Framing & choice architectureFamily 1101Cognitive biasslide 195 (opens in a new tab)
List-length effect

The share of a list we recall falls as the list grows, even as the total recalled rises.

Memory: encoding and retentionFamily 0301Cognitive biasslide 52 (opens in a new tab)
Loaded question

A question is put whose presupposition cannot be rejected by any answer it allows.

Assuming what you are provingFamily 08 · Linguistic03Faulty argumentsslide 92 (opens in a new tab)
Local rationality

People do what makes sense given their goals, their knowledge and their focus of attention at the moment, so an action that looks irrational afterwards was reasonable from inside.

The story told afterwardsFamily 15 · Model02Collective fallaciesslide 212 (opens in a new tab)
Logic-chopping

A fallacy label is used to end an exchange rather than to improve it.

The fallacy charge as a weaponFamily 18 · Procedural03Faulty argumentsslide 174 (opens in a new tab)
Look-elsewhere effect

A result that looks significant may have arisen by chance, because so many hypotheses were tested.

Measurement & research artefactsFamily 1801Cognitive biasslide 261 (opens in a new tab)
Loss aversion

A loss is felt about twice as strongly as an equivalent gain.

Risk, loss & regretFamily 1301Cognitive biasslide 209 (opens in a new tab)
Lucas critique

A relationship estimated under one policy regime cannot be used to predict what a change of regime will do, because the behaviour that produced it will change too.

Targets that eat themselvesFamily 04 · Derived02Collective fallaciesslide 56 (opens in a new tab)
M
The magic number seven

A capacity limit, not a bias: immediate memory holds a handful of chunks, and probably nearer four than seven.

Memory: encoding and retentionFamily 0301Cognitive biasslide 56 (opens in a new tab)
Managing up as displacement

Effort spent shaping how a manager sees the work is rewarded about as well as the work itself, so substituting the first for the second is a rational response to how appraisal is built.

Power & its misuseFamily 18 · Replicated02Collective fallaciesslide 257 (opens in a new tab)
Manufactured scarcity

Availability is restricted, or made to appear restricted, so that the thing is valued more highly and decided on more quickly.

Manufactured consensusFamily 20 · Replicated02Collective fallaciesslide 284 (opens in a new tab)
Masked man

Two terms for the same thing are swapped inside a claim about what somebody knows or believes, and the claim changes truth value.

Arguing against yourselfFamily 09 · Linguistic03Faulty argumentsslide 100 (opens in a new tab)
Masked-man fallacy

Concluding that two things differ because someone knows them under different descriptions.

Argument & inferenceFamily 0701Cognitive biasslide 120 (opens in a new tab)
Mass psychogenic illness

Physical symptoms spread through a group by observation and expectation rather than by any organic agent, most often in closed settings such as schools and factories.

Manias & group delusionsFamily 19 · Replicated02Collective fallaciesslide 261 (opens in a new tab)
Matthew effect

Advantage compounds: an early lead in resources, credit or recognition attracts more of the same, so small initial differences widen into large ones.

Norms & what they make trueFamily 16 · Replicated02Collective fallaciesslide 228 (opens in a new tab)
McNamara fallacy

Measure what is easy, disregard what is not, then treat what cannot be measured as unimportant and finally as non-existent.

Targets that eat themselvesFamily 04 · Maxim02Collective fallaciesslide 59 (opens in a new tab)
Meeting cost blindness

The cost of a meeting is the time of everyone in it, and no budget records that, so meetings are treated as free.

Effort & responsibilityFamily 02 · Law02Collective fallaciesslide 39 (opens in a new tab)
Memory inhibition

Retrieving some material actively suppresses related material that was not retrieved.

Memory: encoding and retentionFamily 0301Cognitive biasslide 41 (opens in a new tab)
Mental accounting

We label money by where it came from and what it is for, then treat the labels as real.

Money, value & ownershipFamily 1201Cognitive biasslide 199 (opens in a new tab)
Mere exposure effect

We come to like things simply because we have encountered them before.

Attention & exposureFamily 0101Cognitive biasslide 16 (opens in a new tab)
Messenger effect

Judging the validity of information by who is delivering it.

Judging other peopleFamily 0901Cognitive biasslide 150 (opens in a new tab)
Metis and techne

The practical knowledge built up by doing a particular job in a particular place cannot be written down as a procedure, and is lost when the procedure replaces it.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 147 (opens in a new tab)
Metric fixation

The belief that measurement can replace judgement, that published numbers secure accountability, and that people are best motivated by rewards tied to those numbers.

Targets that eat themselvesFamily 04 · Model02Collective fallaciesslide 58 (opens in a new tab)
Middle ground

The position between two stated positions is taken to be the correct one because it lies between them.

Framing the choiceFamily 14 · Presumptive03Faulty argumentsslide 141 (opens in a new tab)
Milgram obedience

Ordinary people continued to deliver what they believed were dangerous shocks because a man in a laboratory coat asked them to.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 25 (opens in a new tab)
Millenarian disconfirmation

The claim that believers respond to a publicly failed prophecy by proselytising harder rests on one contaminated case study, and later surveys of failed prophecies find it is not the usual response.

Manias & group delusionsFamily 19 · Disputed02Collective fallaciesslide 272 (opens in a new tab)
Misinformation effect

Information supplied after an event alters what a person remembers seeing.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 70 (opens in a new tab)
Misreading what motivates others

People believe others are moved by money and security while believing themselves moved by interest and mastery.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 81 (opens in a new tab)
Misuse of the average

A figure called the average is offered as the typical case, in a distribution where it is not.

Numbers as premisesFamily 12 · Linguistic03Faulty argumentsslide 129 (opens in a new tab)
Mobbing

One person is singled out for sustained hostile acts by a group of colleagues, so that the harm comes from the pattern and its duration rather than from any single act.

Power & its misuseFamily 18 · Replicated02Collective fallaciesslide 253 (opens in a new tab)
Modality effect

The last few items in a list are recalled better when heard than when read.

Memory: encoding and retentionFamily 0301Cognitive biasslide 42 (opens in a new tab)
Money illusion

We read money at its face value and forget what it will buy.

Money, value & ownershipFamily 1201Cognitive biasslide 206 (opens in a new tab)
Monoculture fragility

A population of near-identical units is efficient and uniformly vulnerable: one pathogen, exploit or design flaw matched to the shared type takes all of it at once.

Drift & accidentFamily 13 · Replicated02Collective fallaciesslide 193 (opens in a new tab)
Mood congruence

Our current mood makes material that matches it easier to recall than material that does not.

Attention & exposureFamily 0101Cognitive biasslide 19 (opens in a new tab)
The moral crumple zone

When a largely automated system fails, responsibility concentrates on the nearest human operator, who had neither the control nor the information to prevent it.

Delegated judgementFamily 14 · Model02Collective fallaciesslide 205 (opens in a new tab)
Moral hazard

Once someone else carries the cost of an outcome, the party who controls it takes less care, and no bad faith is required.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 89 (opens in a new tab)
Moral licensing

Having done something good makes us freer to do something questionable next.

Action, commitment & inertiaFamily 1501Cognitive biasslide 240 (opens in a new tab)
Moral luck

We praise and blame people for outcomes they did not control, which philosophy calls moral luck.

Self-assessment & confidenceFamily 0801Cognitive biasslide 140 (opens in a new tab)
Moral panic

A group or condition is defined as a threat to shared values and the reaction runs ahead of any measured harm, leaving behind institutional changes that outlast the episode.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 262 (opens in a new tab)
Moralistic fallacy

A descriptive conclusion is drawn from a premise about what ought to be the case.

Fact and valueFamily 16 · Formal03Faulty argumentsslide 158 (opens in a new tab)
Moses illusion

A question containing a wrong but fitting term is answered rather than questioned.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 71 (opens in a new tab)
Motivating uncertainty effect

An uncertain reward can motivate us more than a certain one of greater value.

Risk, loss & regretFamily 1301Cognitive biasslide 216 (opens in a new tab)
Motivation crowding-out

Paying people for something they were doing out of duty, reciprocity or identity can reduce how much of it they do.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 74 (opens in a new tab)
Motte and bailey

An ambitious claim that could not survive challenge is advanced under cover of a modest one that can, with the arguer retreating to the modest claim when pressed and returning to the ambitious one when not.

Manufactured consensusFamily 20 · Model02Collective fallaciesslide 288 (opens in a new tab)
Motte-and-bailey

Two claims share a name, one striking and wanted, one modest and defensible, and the arguer occupies whichever the moment requires.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 68 (opens in a new tab)
The moving bottleneck

Relieving the constraint in a flow system does not remove the constraint; it moves to the next resource, and effort spent anywhere else adds cost without adding throughput.

Systems that push backFamily 11 · Model02Collective fallaciesslide 165 (opens in a new tab)
Moving the goalposts

Evidence of the kind demanded is produced, and a further or different demand is substituted for it.

Burden and ignoranceFamily 15 · Procedural03Faulty argumentsslide 151 (opens in a new tab)
MUM effect

People withhold bad news from those it concerns, even when they had nothing to do with it and no reason to fear blame.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 41 (opens in a new tab)
Murphy’s law

The adage that anything that can go wrong will go wrong, sustained by selective memory.

Argument & inferenceFamily 0701Cognitive biasslide 121 (opens in a new tab)
The mythical man-month

The man-month is a unit that assumes people and time can be traded for one another, which holds only for work that requires no communication.

How the work gets shapedFamily 08 · Model02Collective fallaciesslide 118 (opens in a new tab)
N
Naive allocation

We spread resources evenly across whatever set of categories happens to be put in front of us.

Framing & choice architectureFamily 1101Cognitive biasslide 187 (opens in a new tab)
Naive cynicism

We expect other people to be more self-serving than they actually turn out to be.

Belief & evidenceFamily 0601Cognitive biasslide 111 (opens in a new tab)
Naive realism

Believing we see things as they are, so anyone who disagrees must be misinformed or biased.

Belief & evidenceFamily 0601Cognitive biasslide 99 (opens in a new tab)
Naming the burden

Settle who has to show what, before the evidence is discussed.

Moves that workFamily 19 · Repair03Faulty argumentsslide 186 (opens in a new tab)
Naturalistic fallacy

A natural property is offered as the meaning of “good”, so that an evaluative question is answered by a definition.

Fact and valueFamily 16 · Linguistic03Faulty argumentsslide 157 (opens in a new tab)
Near-miss discounting

An event that could have caused harm but did not is filed as evidence that the system works, rather than as evidence that it nearly failed.

Drift & accidentFamily 13 · Replicated02Collective fallaciesslide 197 (opens in a new tab)
Necessary and sufficient

A condition without which the outcome cannot occur is treated as one that brings it about, or the reverse.

CauseFamily 11 · Linguistic03Faulty argumentsslide 119 (opens in a new tab)
Negativity bias

Negative events and feelings affect us more than positive ones of equal size.

Risk, loss & regretFamily 1301Cognitive biasslide 210 (opens in a new tab)
Neglect of probability

Under uncertainty, the probability is not weighted badly — it is not used at all.

Probability & randomnessFamily 0501Cognitive biasslide 90 (opens in a new tab)
Next-in-line effect

We remember little of what happened in the moments just before our own turn to perform.

Memory: encoding and retentionFamily 0301Cognitive biasslide 43 (opens in a new tab)
The ninety-ninety rule

The first 90 per cent of a project takes 90 per cent of the time, and the remaining 10 per cent takes the other 90 per cent.

Projects & their promisesFamily 12 · Law02Collective fallaciesslide 174 (opens in a new tab)
The nirvana fallacy

A workable proposal is rejected by comparison with an ideal that is not among the options.

Framing the choiceFamily 14 · Epistemic03Faulty argumentsslide 140 (opens in a new tab)
No true Scotsman

A counterexample is met by narrowing the definition of the subject term until the counterexample no longer falls under it.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 67 (opens in a new tab)
Noble edge effect

Social responsibility earns a firm goodwill that transfers to judgements of its products.

Social influence & normsFamily 1001Cognitive biasslide 174 (opens in a new tab)
Non-promotable tasks

Work that has to be done but earns nobody a promotion, distributed not by skill but by who is expected to say yes.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 78 (opens in a new tab)
Normal accidents

In systems that are both interactively complex and tightly coupled, serious accidents are a property of the design rather than a failure of the operators, and cannot be engineered away by adding more safety devices.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 190 (opens in a new tab)
Normalcy bias

Underestimating the possibility of disaster and assuming life will continue as normal.

Risk, loss & regretFamily 1301Cognitive biasslide 215 (opens in a new tab)
Normalisation of deviance

A group repeatedly accepts a departure from its own standard without harm, and the departure becomes the standard against which the next one is judged.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 188 (opens in a new tab)
Nostalgia effect

Reminiscing about the past makes money feel less important, and spending easier.

Money, value & ownershipFamily 1201Cognitive biasslide 204 (opens in a new tab)
Not invented here

Ideas, tools and evidence from outside are rejected for being from outside.

Problem-solving & expertiseFamily 1601Cognitive biasslide 247 (opens in a new tab)
Not-invented-here

A group discounts knowledge, tools or solutions because they came from outside it, and pays to rebuild what it could have adopted.

How the work gets shapedFamily 08 · Disputed02Collective fallaciesslide 121 (opens in a new tab)
O
Observer expectancy effect

Expectations held by a researcher change the behaviour of the people being observed.

Measurement & research artefactsFamily 1801Cognitive biasslide 259 (opens in a new tab)
Occam’s razor

A rule for choosing between explanations that fit equally, not a claim that the simple one is true.

Argument & inferenceFamily 0701Cognitive biasslide 122 (opens in a new tab)
Omission bias

We judge harm we caused by acting as worse than the same harm we allowed to happen.

Action, commitment & inertiaFamily 1501Cognitive biasslide 237 (opens in a new tab)
One-sided assessment

A document that undertook to weigh a question presents only the considerations on one side of it.

GeneralisationFamily 10 · Procedural03Faulty argumentsslide 110 (opens in a new tab)
Optimism bias

We rate our own chances of good outcomes too high and of bad ones too low.

Self-assessment & confidenceFamily 0801Cognitive biasslide 134 (opens in a new tab)
The optimism bias uplift

Add a mandated percentage to a project’s own cost estimate at approval, set from the outturn of past projects of the same type, and reduce it only as specific risks are actually retired.

Projects & their promisesFamily 12 · Maxim02Collective fallaciesslide 173 (opens in a new tab)
Organisational silence

Organisational silence is the collective withholding of concerns and dissent, produced by shared beliefs about what it is safe to say rather than by individual timidity.

Voice & silenceFamily 03 · Model02Collective fallaciesslide 43 (opens in a new tab)
Orientation illusions in memory

Which way a familiar object faces is remembered wrongly, confidently, after thousands of exposures.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 72 (opens in a new tab)
Ostrich effect

Avoiding negative information, and avoiding feedback on our own performance.

Risk, loss & regretFamily 1301Cognitive biasslide 214 (opens in a new tab)
Ostrom’s design principles

Commons institutions that last for generations share eight design features, most of which work by making monitoring cheap and defection visible.

Games you are made to playFamily 06 · Replicated02Collective fallaciesslide 87 (opens in a new tab)
Out-group homogeneity

We perceive less variety among members of other groups than among members of our own.

Judging other peopleFamily 0901Cognitive biasslide 160 (opens in a new tab)
Out-of-the-loop performance

An operator who has not been doing the task loses the picture of its current state, and so recovers slowly and badly when handed control.

Delegated judgementFamily 14 · Replicated02Collective fallaciesslide 203 (opens in a new tab)
Outcome bias

Judging a decision by how it turned out rather than by what was knowable when it was made.

Self-assessment & confidenceFamily 0801Cognitive biasslide 133 (opens in a new tab)
Overconfidence effect

Confidence in our judgements exceeds their accuracy, though how much depends heavily on how the questions were chosen.

Self-assessment & confidenceFamily 0801Cognitive biasslide 141 (opens in a new tab)
Overjustification effect

A reward for something we already enjoy can replace the enjoyment as the reason for doing it.

Framing & choice architectureFamily 1101Cognitive biasslide 190 (opens in a new tab)
Overjustification effect

Rewarding an activity someone already chose to do can reduce the chance they choose it again once the reward stops.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 73 (opens in a new tab)
The Overton window

At any moment only a band of policy options can be advocated by someone who wants to stay in office, and what changes a policy is usually the movement of that band rather than an argument about the option.

Norms & what they make trueFamily 16 · Model02Collective fallaciesslide 235 (opens in a new tab)
Overwhelming exception

A generalisation is stated with its force intact and qualified until almost nothing is left inside it.

GeneralisationFamily 10 · Linguistic03Faulty argumentsslide 112 (opens in a new tab)
P
Parasocial trust in AI

Treating human-like chatbots as trusted social partners rather than tools.

AI, automation & delegationFamily 1701Cognitive biasslide 254 (opens in a new tab)
Pareidolia

Seeing a definite thing, most often a face, in material that contains nothing of the kind.

Probability & randomnessFamily 0501Cognitive biasslide 93 (opens in a new tab)
Parkinson’s law

Work expands to fill the time available for it, and administrative staff grows at a rate largely unrelated to the work there is to do.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 99 (opens in a new tab)
Part-set cuing effect

Being shown some of the items you are trying to recall makes the remaining ones harder to retrieve.

Memory: encoding and retentionFamily 0301Cognitive biasslide 44 (opens in a new tab)
Pay-for-performance failure

Paying for measured output reliably raises the measured output, and reliably degrades everything the measure leaves out.

Motivation & its crowdingFamily 05 · Disputed02Collective fallaciesslide 76 (opens in a new tab)
Peak-end rule

We judge an experience by its most intense moment and how it ended, not by its duration.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 58 (opens in a new tab)
Peltzman effect

Safety regulation delivers less than promised because people take more risk once protected.

Risk, loss & regretFamily 1301Cognitive biasslide 217 (opens in a new tab)
Performativity

A theory of human behaviour can make itself true, because people use it to act, and the world then moves towards the model rather than the model towards the world.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 134 (opens in a new tab)
Persuasive definition

A familiar word keeps its emotive force while its descriptive content is quietly changed, so that approval or disapproval is transferred to something new.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 70 (opens in a new tab)
Pessimism bias

Overestimating the chance of bad outcomes and underestimating the chance of good ones.

Self-assessment & confidenceFamily 0801Cognitive biasslide 135 (opens in a new tab)
Peter principle

Promotion on performance in the current job moves people up until they reach one they cannot do, and there they stay.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 100 (opens in a new tab)
Petty tyranny

A manager uses the authority of a small post to control and belittle subordinates in ways that serve the manager rather than the work.

Power & its misuseFamily 18 · Model02Collective fallaciesslide 252 (opens in a new tab)
Picture superiority effect

Concepts studied as pictures are recalled and recognised better than the same concepts studied as words.

Memory: encoding and retentionFamily 0301Cognitive biasslide 45 (opens in a new tab)
The pilot paradox

A pilot succeeds on conditions a rollout cannot reproduce, so the better it is run the less its result tells you.

Projects & their promisesFamily 12 · Law02Collective fallaciesslide 179 (opens in a new tab)
The pilot-to-scale gap

Effects measured in small trials run by the people who designed a programme shrink, often to nothing, when it is evaluated independently at scale.

Projects & their promisesFamily 12 · Replicated02Collective fallaciesslide 181 (opens in a new tab)
Placebo effect

Improvement produced by the expectation of a treatment rather than by the treatment.

Measurement & research artefactsFamily 1801Cognitive biasslide 262 (opens in a new tab)
Planning fallacy

Underestimating how long a task will take, and what it will cost and risk.

Time & the future selfFamily 1401Cognitive biasslide 227 (opens in a new tab)
Pluralistic ignorance

Privately rejecting a norm while assuming that almost everyone else accepts it.

Social influence & normsFamily 1001Cognitive biasslide 170 (opens in a new tab)
Pluralistic ignorance

A group sustains a norm that most of its members privately reject, because each believes the others accept it.

Agreement without beliefFamily 01 · Replicated02Collective fallaciesslide 12 (opens in a new tab)
Poisoning the well

Adverse information about the arguer is supplied before he speaks, so that whatever he says arrives already discounted.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 14 (opens in a new tab)
Policy resistance

A system pushed towards one actor’s goal pushes back, because everyone else acting on it works harder to restore the position they wanted.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 148 (opens in a new tab)
Policy-based evidence

Evidence is commissioned, selected and timed to support a decision already taken, so the appearance of an evidence base survives while its function does not.

Legitimacy over functionFamily 09 · Law02Collective fallaciesslide 133 (opens in a new tab)
Pollyanna principle

Pleasant material is processed, judged and recalled more readily than unpleasant material of the same intensity.

Self-assessment & confidenceFamily 0801Cognitive biasslide 142 (opens in a new tab)
Positive conclusion from a negative premise

An affirmative conclusion is drawn where one of the premises denies rather than affirms.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 85 (opens in a new tab)
Positivity effect

Older adults attend to and remember positive material more than negative, relative to younger adults.

Self-assessment & confidenceFamily 0801Cognitive biasslide 143 (opens in a new tab)
Post hoc ergo propter hoc

One event is taken to have caused another because it came first.

CauseFamily 11 · Presumptive03Faulty argumentsslide 114 (opens in a new tab)
Post-purchase rationalisation

After choosing, we upgrade what we bought and downgrade what we turned down.

Money, value & ownershipFamily 1201Cognitive biasslide 207 (opens in a new tab)
Pournelle’s iron law of bureaucracy

In any bureaucracy, those devoted to the organisation itself come to control it, and those devoted to its stated purpose lose influence.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 103 (opens in a new tab)
Practical drift

Groups quietly adapt written procedure to the conditions they usually face, and the adaptations only collide on the day the groups are coupled tightly together.

How the work gets shapedFamily 08 · Model02Collective fallaciesslide 126 (opens in a new tab)
Precedential slippery slope

A decision is opposed not for its own consequences but for what it would commit the decider to next.

CauseFamily 11 · Presumptive03Faulty argumentsslide 121 (opens in a new tab)
Preference falsification

People state a public position they do not hold in order to avoid social cost, so public opinion can diverge sharply and invisibly from private opinion.

Agreement without beliefFamily 01 · Model02Collective fallaciesslide 13 (opens in a new tab)
Prejudice

An evaluation of a person that follows from the category they are assigned to.

Judging other peopleFamily 0901Cognitive biasslide 166 (opens in a new tab)
Present bias

Giving disproportionate weight to rewards that arrive sooner, even when a larger payoff is available later.

Time & the future selfFamily 1401Cognitive biasslide 223 (opens in a new tab)
Presenteeism

Attending work while ill, produced by the structure of cover and absence rules rather than by dedication.

Motivation & its crowdingFamily 05 · Replicated02Collective fallaciesslide 79 (opens in a new tab)
Primacy effect

We remember what came first better than anything that follows, and judge the rest against it.

Memory: encoding and retentionFamily 0301Cognitive biasslide 32 (opens in a new tab)
Priming

Exposure to one stimulus changes the response to a later one, with no awareness of the link.

Attention & exposureFamily 0101Cognitive biasslide 15 (opens in a new tab)
Principal–agent problem

When one party acts for another, cannot be fully observed and does not share its objectives, no contract removes the resulting loss; it can only be traded against risk.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 91 (opens in a new tab)
The principle of charity

Argue against the strongest version of what the other party said, including the parts they left out.

Moves that workFamily 19 · Repair03Faulty argumentsslide 182 (opens in a new tab)
Prisoner’s dilemma

A two-player game in which defection pays better than cooperation whatever the other side does, leaving both worse off than if both had cooperated.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 83 (opens in a new tab)
Pro-innovation bias

An innovation is assumed to benefit everyone, and non-adoption is treated as a failure to be overcome.

Problem-solving & expertiseFamily 1601Cognitive biasslide 248 (opens in a new tab)
Processing difficulty effect

Material that costs more effort to process is sometimes better retained, but only certain kinds of effort.

Memory: encoding and retentionFamily 0301Cognitive biasslide 55 (opens in a new tab)
Projection bias

Overestimating how much our future selves will share our current beliefs, values and behaviour.

Time & the future selfFamily 1401Cognitive biasslide 224 (opens in a new tab)
Proof by verbosity

The argument is made too long and too dense to be examined, and the difficulty of examining it is taken for strength.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 165 (opens in a new tab)
Proving too much

An argument is shown to be defective by showing that its form would equally establish something the arguer rejects.

Burden and ignoranceFamily 15 · Presumptive03Faulty argumentsslide 154 (opens in a new tab)
Proximate and ultimate

An explanation at one causal level is offered as refuting an explanation at another.

CauseFamily 11 · Linguistic03Faulty argumentsslide 122 (opens in a new tab)
Pseudocertainty effect

An outcome that is certain only if an earlier stage goes well is treated as certain outright.

Probability & randomnessFamily 0501Cognitive biasslide 91 (opens in a new tab)
Psychological essentialism

We treat a category as having a hidden inner nature that explains what its members are like.

Judging other peopleFamily 0901Cognitive biasslide 164 (opens in a new tab)
Psychological reactance

A threatened freedom is reasserted, and the blocked option becomes more attractive for being blocked.

Action, commitment & inertiaFamily 1501Cognitive biasslide 239 (opens in a new tab)
Psychological safety

Psychological safety is a belief shared within a team that speaking up with a question, a doubt or an admitted error will not be held against you.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 44 (opens in a new tab)
Publication bias

Studies with positive results reach print; studies that found nothing stay in the drawer.

Measurement & research artefactsFamily 1801Cognitive biasslide 263 (opens in a new tab)
Purity spiral

Where status comes from demonstrating commitment and nobody gains by arguing for less, the standard ratchets upward until ordinary members are disqualified by a standard they helped to set.

Norms & what they make trueFamily 16 · Law02Collective fallaciesslide 234 (opens in a new tab)
Putt’s law

Technical organisations divide into those who understand what they do not manage and those who manage what they do not understand.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 102 (opens in a new tab)
Pygmalion effect

Expectations held by others can become self-fulfilling, though the classroom effect is far smaller than its fame suggests.

Judging other peopleFamily 0901Cognitive biasslide 151 (opens in a new tab)
Pygmalion effect

Teachers told that particular pupils were about to bloom were reported to raise those pupils’ measured ability, an effect the later evidence has cut down sharply.

Norms & what they make trueFamily 16 · Disputed02Collective fallaciesslide 224 (opens in a new tab)
Q
The queen bee phenomenon

Women who have reached senior posts in a male-dominated organisation distance themselves from junior women and judge them more harshly than their male colleagues do.

Sorting & the ladderFamily 17 · Disputed02Collective fallaciesslide 244 (opens in a new tab)
Question-begging definition

A term is defined so that the disputed conclusion follows from the meaning rather than from any evidence.

Assuming what you are provingFamily 08 · Linguistic03Faulty argumentsslide 91 (opens in a new tab)
Question-begging language (loaded words)

The conclusion is carried by the choice of words rather than by anything asserted, so that accepting the description concedes the argument.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 74 (opens in a new tab)
R
Ratchet effect

When current output sets the next target, people hold back: good work today is paid for with a harder standard tomorrow.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 61 (opens in a new tab)
Reactive devaluation

Discounting a proposal because of who made it, particularly an adversary.

Social influence & normsFamily 1001Cognitive biasslide 172 (opens in a new tab)
Recency effect

We remember and weight what came last more heavily than what came earlier.

Memory: encoding and retentionFamily 0301Cognitive biasslide 33 (opens in a new tab)
Recency in performance review

Reviews are widely believed to weight the final weeks of the period far above the rest; the appraisal evidence finds that the standing impression does most of the work and that the direction of the timing effect is not fixed.

Sorting & the ladderFamily 17 · Disputed02Collective fallaciesslide 238 (opens in a new tab)
The recovered-memory panic

Therapeutic techniques adopted from the late 1980s to recover repressed memories of abuse are the same procedures that in the laboratory reliably generate confident memories of events that did not occur.

Manias & group delusionsFamily 19 · Replicated02Collective fallaciesslide 269 (opens in a new tab)
Red herring

The subject under discussion is replaced by a different subject, and the replacement is not announced.

DiversionFamily 03 · Procedural03Faulty argumentsslide 37 (opens in a new tab)
Red Queen effect

Everyone improves, so nobody gains: effort rises across a whole field while relative position stays exactly where it was.

Games you are made to playFamily 06 · Model02Collective fallaciesslide 95 (opens in a new tab)
Reductio ad Hitlerum

A position is refuted by pointing out that the Nazis, or some comparable party, also held it.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 16 (opens in a new tab)
Reference-class forecasting

Forecast a project from the outturn distribution of similar completed projects rather than from an estimate assembled out of its own details.

Projects & their promisesFamily 12 · Maxim02Collective fallaciesslide 172 (opens in a new tab)
Refuting the example

An illustration offered in support of a claim is defeated, and the claim is treated as defeated with it.

Analogy and comparisonFamily 13 · Epistemic03Faulty argumentsslide 134 (opens in a new tab)
The regression fallacy

A movement back towards the average is explained by whatever happened in between.

Numbers as premisesFamily 12 · Presumptive03Faulty argumentsslide 128 (opens in a new tab)
Regression in company performance

Exceptional company performance is part signal and part luck, so extreme results move back towards the average whatever anyone does, and the practices credited for the peak are blamed for the fall.

The story told afterwardsFamily 15 · Replicated02Collective fallaciesslide 218 (opens in a new tab)
Regret aversion

Making a decision in order not to regret the alternative later.

Risk, loss & regretFamily 1301Cognitive biasslide 213 (opens in a new tab)
Regulatory capture

An agency created to regulate an industry comes to act in that industry’s interest, not usually through corruption but because the industry is the only constituency that turns up.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 138 (opens in a new tab)
Reification

An abstraction, a construct or a statistic is treated as a concrete thing with properties and powers of its own.

Definition as a weaponFamily 06 · Linguistic03Faulty argumentsslide 73 (opens in a new tab)
Relativist fallacy

A claim is conceded as true for the speaker and denied for the hearer, so that a disagreement is dissolved rather than settled.

Fact and valueFamily 16 · Linguistic03Faulty argumentsslide 160 (opens in a new tab)
Rent-seeking

Where a prize can be won by effort rather than earned by production, the effort spent competing for it is pure loss, and it can consume the whole prize.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 92 (opens in a new tab)
Representativeness heuristic

We judge probability by how closely a case resembles a mental prototype.

Probability & randomnessFamily 0501Cognitive biasslide 79 (opens in a new tab)
Requirement churn

Requirements that keep changing after design has begun impose rework whose cost rises with everything already built on the version being replaced.

Projects & their promisesFamily 12 · Replicated02Collective fallaciesslide 178 (opens in a new tab)
Resort to humour or ridicule

The argument is answered with a joke, and the laughter is allowed to stand in place of a reply.

DiversionFamily 03 · Procedural03Faulty argumentsslide 44 (opens in a new tab)
Resource inertia

Organisations reallocate resources far less than their stated strategy implies.

Action, commitment & inertiaFamily 1501Cognitive biasslide 238 (opens in a new tab)
Response bias

Giving inaccurate or false answers to self-report questions in surveys and structured interviews.

Measurement & research artefactsFamily 1801Cognitive biasslide 260 (opens in a new tab)
Restraint bias

Overestimating our ability to resist temptation — and therefore exposing ourselves to more of it.

Time & the future selfFamily 1401Cognitive biasslide 228 (opens in a new tab)
Reverse causation

The effect is named as the cause and the cause as the effect.

CauseFamily 11 · Presumptive03Faulty argumentsslide 117 (opens in a new tab)
Reverse psychology

Advocating the opposite of what you want, so the other person asserts their freedom by choosing it.

Social influence & normsFamily 1001Cognitive biasslide 178 (opens in a new tab)
The revolving door

Officials move between government and the industries they oversee, and while the connections they carry have a measurable price, the softened enforcement usually attributed to the door has been hard to find.

Legitimacy over functionFamily 09 · Disputed02Collective fallaciesslide 139 (opens in a new tab)
Rewarding A while hoping for B

Organisations routinely pay for one behaviour while hoping for another, and then are surprised to get the one they paid for.

Targets that eat themselvesFamily 04 · Law02Collective fallaciesslide 62 (opens in a new tab)
Rhyme-as-reason effect

Statements that rhyme are judged more true than the same claims in prose.

Argument & inferenceFamily 0701Cognitive biasslide 123 (opens in a new tab)
Risk compensation

People adjust how much risk they take to keep their felt level of risk roughly where it was.

Risk, loss & regretFamily 1301Cognitive biasslide 218 (opens in a new tab)
Risky shift

Groups were long held to take riskier decisions than their members would take alone, a claim the later evidence did not sustain.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 19 (opens in a new tab)
The root-cause fallacy

An accident in a complex system has no single root cause, only a set of conditions that had to coincide, so a search for one will always find something and always stop too early.

The story told afterwardsFamily 15 · Maxim02Collective fallaciesslide 211 (opens in a new tab)
Rosy retrospection

We remember experiences more favourably than we experienced them, and the past more fondly than the present.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 63 (opens in a new tab)
Rule accretion

Rules are added faster than they are removed, so procedure accumulates until the burden bears little relation to the risks that produced it.

Laws of growth & decayFamily 07 · Replicated02Collective fallaciesslide 108 (opens in a new tab)
Rumour transmission

A rumour is not a message decaying as it passes down a chain but a group building an explanation for something it needs explained, and its accuracy depends on whether the network contains anyone who can check it.

Manias & group delusionsFamily 19 · Disputed02Collective fallaciesslide 267 (opens in a new tab)
The runaway train

A sequence of steps is taken so rapidly and with such momentum that no individual step is examined.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 170 (opens in a new tab)
S
Safety-I and Safety-II

Safety can be defined as the absence of accidents, which directs attention to the rare cases that go wrong, or as the capacity to succeed under varying conditions, which directs attention to the ordinary work that goes right.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 195 (opens in a new tab)
Salience bias

We attend to whatever stands out and discount whatever does not, regardless of importance.

Attention & exposureFamily 0101Cognitive biasslide 12 (opens in a new tab)
The satanic panic

A circulating legend of organised ritual abuse acquired investigative and therapeutic machinery that produced the accounts it was looking for, and no verified instance was ever found.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 270 (opens in a new tab)
Scope creep

Deliverables grow by increments small enough that none triggers a re-plan, until the total is unrecognisable and the date has not moved.

Projects & their promisesFamily 12 · Law02Collective fallaciesslide 177 (opens in a new tab)
Sealioning

Relentless, courteous requests for evidence are used to exhaust rather than to learn.

Overwhelming and exhaustingFamily 17 · Procedural03Faulty argumentsslide 167 (opens in a new tab)
Second-system effect

The second system a designer builds is the most dangerous, because it collects every embellishment the first one had no room for.

How the work gets shapedFamily 08 · Law02Collective fallaciesslide 119 (opens in a new tab)
Selective perception

We notice and retain what fits our commitments and let discrepant material pass unregistered.

Attention & exposureFamily 0101Cognitive biasslide 20 (opens in a new tab)
The self-destructive argument method

Turn the argument on the position it was offered to support, and show that it defeats itself.

Moves that workFamily 19 · Repair03Faulty argumentsslide 184 (opens in a new tab)
Self-fulfilling prophecy

A definition of a situation that is false to begin with calls out behaviour that makes it true, and the outcome is then read as proof that the definition was right all along.

Norms & what they make trueFamily 16 · Model02Collective fallaciesslide 222 (opens in a new tab)
Self-reference effect

Material judged against ourselves is remembered better than the same material processed for meaning alone.

Memory: encoding and retentionFamily 0301Cognitive biasslide 46 (opens in a new tab)
Self-serving bias

We claim our successes as ours and push our failures onto circumstances.

Self-assessment & confidenceFamily 0801Cognitive biasslide 131 (opens in a new tab)
Semmelweis reflex

The reflex rejection of new evidence because it contradicts established practice.

Belief & evidenceFamily 0601Cognitive biasslide 106 (opens in a new tab)
Semmelweis reflex

An institution rejects a finding, and often the person who brought it, because accepting it would indict the practice the institution already follows.

Voice & silenceFamily 03 · Law02Collective fallaciesslide 48 (opens in a new tab)
Serial position effect

We remember the first and last items in a sequence and lose the middle.

Memory: encoding and retentionFamily 0301Cognitive biasslide 31 (opens in a new tab)
Serial recall effect

Recalling items in their original order is a separate capacity from recalling the items themselves.

Memory: encoding and retentionFamily 0301Cognitive biasslide 47 (opens in a new tab)
Sexual overperception bias

Overestimating another person’s sexual interest in oneself — predominantly in men.

Judging other peopleFamily 0901Cognitive biasslide 153 (opens in a new tab)
Shifting the burden

A symptomatic remedy relieves the problem well enough that the fundamental capability is never built, and then cannot be.

Systems that push backFamily 11 · Model02Collective fallaciesslide 157 (opens in a new tab)
Shifting the burden of proof

The party who made the claim requires the other party to disprove it.

Burden and ignoranceFamily 15 · Procedural03Faulty argumentsslide 146 (opens in a new tab)
Shirky principle

Organisations come to protect the problem that justifies their existence.

Laws of growth & decayFamily 07 · Law02Collective fallaciesslide 105 (opens in a new tab)
Shooting the messenger

The bearer of bad news is judged worse for having borne it, and everyone watching learns not to be next.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 42 (opens in a new tab)
The silo effect

Units created to specialise acquire their own goals, measures and vocabulary, and then withhold from each other the information that only the whole organisation can use.

Laws of growth & decayFamily 07 · Model02Collective fallaciesslide 111 (opens in a new tab)
The similar-to-me effect

Raters judge people they perceive as similar to themselves more favourably, and the similarity that does the work is one of attitude and outlook rather than of demography.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 240 (opens in a new tab)
Simpson’s paradox

An association present in every subgroup can reverse when the subgroups are pooled.

Targets that eat themselvesFamily 04 · Derived02Collective fallaciesslide 70 (opens in a new tab)
Social comparison bias

We judge ourselves against the people around us, and resent those the comparison places above us.

Social influence & normsFamily 1001Cognitive biasslide 179 (opens in a new tab)
Social desirability bias

People report the answer that looks good rather than the answer that is true.

Measurement & research artefactsFamily 1801Cognitive biasslide 264 (opens in a new tab)
Social facilitation

The presence of other people speeds up performance on a task you have mastered and degrades it on one you have not.

Effort & responsibilityFamily 02 · Replicated02Collective fallaciesslide 37 (opens in a new tab)
Social loafing

Individual effort falls as a group grows, whenever no one can see who contributed what.

Effort & responsibilityFamily 02 · Replicated02Collective fallaciesslide 29 (opens in a new tab)
Social norms

Collectively held beliefs about which behaviour is appropriate in a given situation.

Social influence & normsFamily 1001Cognitive biasslide 169 (opens in a new tab)
Social proof

People take what others around them are doing as evidence of what is correct, so a practice can spread through an organisation on the strength of its adoption count alone.

Norms & what they make trueFamily 16 · Replicated02Collective fallaciesslide 231 (opens in a new tab)
Solutionism

The habit of recasting a complex, contested situation as a neat problem that happens to fit the tools already to hand.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 153 (opens in a new tab)
Source confusion

A memory error in which we cannot recall where a memory came from.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 60 (opens in a new tab)
The sources of unintended consequences

Purposive action produces outcomes nobody intended, and those outcomes come from a small number of sources that can be listed in advance.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 145 (opens in a new tab)
Spacing effect

Repetitions spread over time are remembered far better than the same repetitions crammed together.

Memory: encoding and retentionFamily 0301Cognitive biasslide 35 (opens in a new tab)
Span of control

The number of people reporting to one manager fixes how many layers an organisation needs, and the classical answer of five or six was a doctrine rather than a measurement.

Laws of growth & decayFamily 07 · Model02Collective fallaciesslide 110 (opens in a new tab)
Special pleading

A rule accepted as general is applied to others and an exemption is claimed in one’s own case without a relevant difference being given.

Burden and ignoranceFamily 15 · Procedural03Faulty argumentsslide 152 (opens in a new tab)
Speculative mania

A credit-fed price rise in which the reason to buy is that others are buying, running through a standard sequence to a point at which everyone tries to sell at once.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 264 (opens in a new tab)
Spiral of silence

People who believe their view is losing ground in public become less willing to express it, which makes the view appear weaker still.

Agreement without beliefFamily 01 · Disputed02Collective fallaciesslide 14 (opens in a new tab)
The sponsorship gap

Women and minority staff receive advice and encouragement as often as their peers but are less often advocated for by someone with the standing to allocate a post.

Sorting & the ladderFamily 17 · Replicated02Collective fallaciesslide 246 (opens in a new tab)
Spotlight effect

We think other people notice and remember our appearance and slips far more than they do.

Self-assessment & confidenceFamily 0801Cognitive biasslide 130 (opens in a new tab)
Stag hunt

A game with two stable outcomes — everyone cooperates, or everyone plays safe — in which the safe outcome can win despite being worse for all.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 84 (opens in a new tab)
Status quo bias

We prefer things to stay as they are, and treat the default as the safe choice.

Action, commitment & inertiaFamily 1501Cognitive biasslide 234 (opens in a new tab)
Steel-manning

State the other side’s case better than they did, and then answer that.

Moves that workFamily 19 · Repair03Faulty argumentsslide 183 (opens in a new tab)
Stereotype threat

People at risk of confirming a negative stereotype about their group are held to perform worse on tests when that stereotype is made salient.

Norms & what they make trueFamily 16 · Disputed02Collective fallaciesslide 227 (opens in a new tab)
Stereotyping

A category, once applied to a person, supplies expectations about what has not been observed.

Judging other peopleFamily 0901Cognitive biasslide 165 (opens in a new tab)
Stolen concept

A concept is used in the act of denying something the concept depends on.

Assuming what you are provingFamily 08 · Epistemic03Faulty argumentsslide 93 (opens in a new tab)
Strategic misrepresentation

Forecasts attached to a proposal are shaped by what will win approval, so the numbers that reach the decision are optimistic by design rather than by accident.

Projects & their promisesFamily 12 · Model02Collective fallaciesslide 171 (opens in a new tab)
Straw man

The opponent’s position is restated in a weaker form and the weaker form is refuted.

DiversionFamily 03 · Procedural03Faulty argumentsslide 38 (opens in a new tab)
Streetlight effect

We search where the data is easy to collect rather than where the answer is likely to be.

Attention & exposureFamily 0101Cognitive biasslide 22 (opens in a new tab)
Student syndrome

Work that is given a padded deadline is started at the last moment the deadline allows, so the padding is spent before the work begins.

Projects & their promisesFamily 12 · Law02Collective fallaciesslide 175 (opens in a new tab)
Sub-optimisation

Optimising each part of a system on its own measure degrades the whole, because the parts are coupled and their local optima conflict.

Systems that push backFamily 11 · Derived02Collective fallaciesslide 164 (opens in a new tab)
Subadditivity effect

Naming the parts of a category raises its total judged probability above the whole.

Probability & randomnessFamily 0501Cognitive biasslide 92 (opens in a new tab)
Subjective validation

A statement feels accurate because it means something to us, not because it fits.

Belief & evidenceFamily 0601Cognitive biasslide 107 (opens in a new tab)
Subjectivist fallacy

A claim with a truth-value is reclassified as a matter of taste, and thereby placed beyond assessment.

Fact and valueFamily 16 · Procedural03Faulty argumentsslide 159 (opens in a new tab)
Success to the successful

Two parties draw on one pool of resource, and an early advantage to either is converted into the resources that produce the next advantage.

Systems that push backFamily 11 · Model02Collective fallaciesslide 159 (opens in a new tab)
Sucker effect

People withdraw effort not from laziness but to avoid being the one who carries someone who is not pulling.

Effort & responsibilityFamily 02 · Replicated02Collective fallaciesslide 31 (opens in a new tab)
Suffix effect

One irrelevant spoken word at the end of a heard list destroys the recall advantage of its last items.

Memory: encoding and retentionFamily 0301Cognitive biasslide 53 (opens in a new tab)
Suggestibility

Accepting and acting on ideas suggested by others, without independent checking.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 61 (opens in a new tab)
Sunk cost fallacy

We keep going because of what we have already spent, not because continuing is worth it.

Action, commitment & inertiaFamily 1501Cognitive biasslide 235 (opens in a new tab)
Surrogation

People replace the thing they care about with the measure of it, and then stop being able to tell the difference.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 57 (opens in a new tab)
Survivorship bias

Mistaking a successful subgroup for the whole group, because the failures are invisible.

Probability & randomnessFamily 0501Cognitive biasslide 82 (opens in a new tab)
Survivorship in best practice

Guidance drawn only from organisations that succeeded cannot say which of their practices mattered, because the ones that did the same things and failed were never in the sample.

The story told afterwardsFamily 15 · Derived02Collective fallaciesslide 217 (opens in a new tab)
Swimmer’s body illusion

We mistake a selection criterion for an effect of the activity we admire.

Measurement & research artefactsFamily 1801Cognitive biasslide 266 (opens in a new tab)
The Swiss cheese model

An accident requires a momentary alignment of holes in several successive layers of defence, so the useful question is why the defences were weak rather than who made the final error.

Drift & accidentFamily 13 · Model02Collective fallaciesslide 189 (opens in a new tab)
Sycophancy

Agreement supplied upward because it is rewarded, which leaves a leader with a record of confirmation and no record of dissent.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 50 (opens in a new tab)
System justification

People defend the existing social order even when it works against them.

Belief & evidenceFamily 0601Cognitive biasslide 108 (opens in a new tab)
T
Take-the-best heuristic

We decide between two options on the first cue that tells them apart, and ignore the rest.

Problem-solving & expertiseFamily 1601Cognitive biasslide 246 (opens in a new tab)
Teaching to the test

Instruction moves toward the specific form of the examination, so scores rise faster than the learning they are supposed to represent.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 63 (opens in a new tab)
Technical debt

A shortcut taken to ship sooner leaves a structure that costs more to change, and the extra cost is paid on every later change until it is repaid.

How the work gets shapedFamily 08 · Model02Collective fallaciesslide 127 (opens in a new tab)
Technocentrism

The habit of asking what a technology does to people, as though the technology acted alone and the arrangements around it were incidental.

Before you move the fenceFamily 10 · Model02Collective fallaciesslide 154 (opens in a new tab)
Telescoping effect

We misplace events in time: recent ones feel remote, and remote ones feel recent.

Memory: distortion and reconstructionFamily 0401Cognitive biasslide 62 (opens in a new tab)
Testing effect

Retrieving material from memory improves later retention more than restudying it for the same time.

Memory: encoding and retentionFamily 0301Cognitive biasslide 48 (opens in a new tab)
Texas sharpshooter

The hypothesis is drawn round the data after the data have been seen, and then tested on the same data.

GeneralisationFamily 10 · Epistemic03Faulty argumentsslide 108 (opens in a new tab)
Third-person effect

We think persuasive media affect other people more than they affect us, and we legislate on that belief.

Self-assessment & confidenceFamily 0801Cognitive biasslide 144 (opens in a new tab)
The Thomas theorem

If people define situations as real, they are real in their consequences, whatever the situation actually is.

Norms & what they make trueFamily 16 · Law02Collective fallaciesslide 223 (opens in a new tab)
Thought-terminating cliché

A short, final-sounding phrase is produced where an argument would have to begin, and the question closes.

DiversionFamily 03 · Procedural03Faulty argumentsslide 46 (opens in a new tab)
Tick-box compliance

Organisations adopt the visible form of a requirement while the practice it was meant to change stays exactly where it was.

Targets that eat themselvesFamily 04 · Replicated02Collective fallaciesslide 67 (opens in a new tab)
Time-saving bias

We badly misjudge the time gained by going faster, especially when already going fast.

Time & the future selfFamily 1401Cognitive biasslide 229 (opens in a new tab)
Tip of the tongue

A word we cannot produce but can partly describe, felt as being just out of reach.

Memory: encoding and retentionFamily 0301Cognitive biasslide 49 (opens in a new tab)
Tokenism

Where a group contains only a few members of a visibly different category, those few are treated as representatives of the category rather than as individuals.

Sorting & the ladderFamily 17 · Model02Collective fallaciesslide 245 (opens in a new tab)
Tone policing

The manner in which an argument was made is treated as a reason not to address it.

The fallacy charge as a weaponFamily 18 · Procedural03Faulty argumentsslide 176 (opens in a new tab)
The Toulmin layout

Six parts — claim, grounds, warrant, backing, qualifier, rebuttal — that make visible the step an argument usually leaves out.

Moves that workFamily 19 · Repair03Faulty argumentsslide 181 (opens in a new tab)
The toxic handler

Someone absorbs and neutralises the anger, anxiety and disappointment that decisions elsewhere in the organisation generate, at a cost that appears in no account and no job description.

Power & its misuseFamily 18 · Model02Collective fallaciesslide 254 (opens in a new tab)
Tragedy of the anticommons

When too many parties each hold a right to exclude, a resource is used far too little, which is the mirror image of the commons.

Games you are made to playFamily 06 · Derived02Collective fallaciesslide 88 (opens in a new tab)
Tragedy of the commons

The claim that a shared resource is inevitably destroyed by its users unless it is privatised or policed, which holds for open access and not for commons.

Games you are made to playFamily 06 · Disputed02Collective fallaciesslide 86 (opens in a new tab)
Trained incapacity

The training that makes people competent in the normal case is what stops them seeing the abnormal one.

Laws of growth & decayFamily 07 · Model02Collective fallaciesslide 107 (opens in a new tab)
Trait ascription bias

We see our own behaviour as varying with the situation and other people as acting from fixed traits.

Judging other peopleFamily 0901Cognitive biasslide 161 (opens in a new tab)
Trickle-down hostility

Hostile treatment a manager receives from their own superior is passed down the hierarchy, so conduct at the top of an organisation reappears at the bottom.

Power & its misuseFamily 18 · Replicated02Collective fallaciesslide 251 (opens in a new tab)
Trivial objections

A minor and genuine defect in a case is treated as sufficient reason to reject the whole of it.

DiversionFamily 03 · Presumptive03Faulty argumentsslide 43 (opens in a new tab)
Tu quoque

The argument is answered by showing that the arguer does not live by it.

Attacking the arguerFamily 01 · Presumptive03Faulty argumentsslide 13 (opens in a new tab)
Tulip mania

The Dutch bulb trade of 1636–37 is the standard illustration of mass financial madness, and most of the detail usually given for it was invented two centuries afterwards.

Manias & group delusionsFamily 19 · Disputed02Collective fallaciesslide 265 (opens in a new tab)
U
Ultimate attribution error

Good acts by our group are credited to character and by other groups to circumstance, and bad acts reverse.

Judging other peopleFamily 0901Cognitive biasslide 162 (opens in a new tab)
Unaccepted enthymeme

An argument is left with a premise unstated which the audience does not in fact grant.

Assuming what you are provingFamily 08 · Epistemic03Faulty argumentsslide 94 (opens in a new tab)
Undistributed middle

Two classes are linked through a shared term that was never taken in its whole extent.

Invalid by formFamily 07 · Formal03Faulty argumentsslide 81 (opens in a new tab)
Unfalsifiability

A claim is put in a form that no possible observation could count against, and its immunity is then offered as its strength.

Burden and ignoranceFamily 15 · Epistemic03Faulty argumentsslide 149 (opens in a new tab)
Unit bias

We treat whatever counts as one portion as the right amount to take.

Framing & choice architectureFamily 1101Cognitive biasslide 194 (opens in a new tab)
Unrepresentative sample

A generalisation is drawn from cases selected in a way that is related to what is being measured.

GeneralisationFamily 10 · Presumptive03Faulty argumentsslide 104 (opens in a new tab)
Unwarranted assumption

An argument rests on a proposition that is neither stated, defended, nor of a kind that could safely be taken for granted.

Assuming what you are provingFamily 08 · Epistemic03Faulty argumentsslide 95 (opens in a new tab)
Up-or-out

An organisation promotes from within on a fixed clock and requires anyone not promoted by the deadline to leave.

Sorting & the ladderFamily 17 · Model02Collective fallaciesslide 248 (opens in a new tab)
Upward filtering

Each layer of a hierarchy passes on the version of events it can defend, so the account that reaches the top is not the account that was sent.

Voice & silenceFamily 03 · Model02Collective fallaciesslide 47 (opens in a new tab)
The urban legend

A story told as true, set locally and sourced to a friend of a friend, which persists because the versions that provoke disgust or fear are passed on more often than the versions that are accurate.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 268 (opens in a new tab)
The utilisation trap

As a resource is loaded towards full capacity, waiting time rises without limit, so the last few percentage points of utilisation cost far more than they return.

Systems that push backFamily 11 · Derived02Collective fallaciesslide 166 (opens in a new tab)
V
Vetocracy

When enough actors hold a right to block and none holds a right to decide, the status quo wins by default and reform is bought rather than chosen.

Legitimacy over functionFamily 09 · Model02Collective fallaciesslide 136 (opens in a new tab)
Von Restorff effect

An item that differs from a uniform set around it is remembered better than the rest.

Memory: encoding and retentionFamily 0301Cognitive biasslide 50 (opens in a new tab)
W
Watermelon reporting

A programme is reported green at every level while the work underneath it is red, because each reviewer rates the report rather than the thing.

Voice & silenceFamily 03 · Law02Collective fallaciesslide 46 (opens in a new tab)
Weak man (nut-picking)

The feeblest real holder of a position is selected, defeated, and the defeat reported as a defeat of the position.

DiversionFamily 03 · Epistemic03Faulty argumentsslide 39 (opens in a new tab)
Weber–Fechner law

A change must be a constant proportion of what is already there before we notice it at all.

Framing & choice architectureFamily 1101Cognitive biasslide 193 (opens in a new tab)
Well-travelled road effect

A familiar route feels shorter than an unfamiliar one of the same length.

Time & the future selfFamily 1401Cognitive biasslide 230 (opens in a new tab)
Whataboutism

A charge is met not with a defence but with a counter-charge about the accuser or their side, so the question of what happened is replaced by a comparison of records.

Manufactured consensusFamily 20 · Law02Collective fallaciesslide 287 (opens in a new tab)
Whataboutism

A charge is met with a charge against the accuser, and the first charge is left where it fell.

DiversionFamily 03 · Procedural03Faulty argumentsslide 42 (opens in a new tab)
The whistleblower’s dilemma

The person who reports serious wrongdoing carries the cost alone while the benefit is spread across everyone else, which is why most people who see it say nothing.

Voice & silenceFamily 03 · Replicated02Collective fallaciesslide 49 (opens in a new tab)
Winner’s curse

In a contest for something of uncertain but common value, the winner is usually the bidder who overestimated it by the most.

Games you are made to playFamily 06 · Replicated02Collective fallaciesslide 96 (opens in a new tab)
Wishful thinking

A proposition is believed because it would be good if it were so.

Pressure instead of proofFamily 04 · Epistemic03Faulty argumentsslide 54 (opens in a new tab)
Witch-hunt dynamics

An accusation system in which denial counts as evidence of guilt and confession buys leniency in exchange for naming others will grow until an authority changes the rules of evidence.

Manias & group delusionsFamily 19 · Model02Collective fallaciesslide 266 (opens in a new tab)
Work-as-imagined and work-as-done

The work as described in procedures and the work as actually done diverge, because a procedure cannot contain all the variability the work contains.

How the work gets shapedFamily 08 · Model02Collective fallaciesslide 125 (opens in a new tab)
Z
Zero-risk bias

Preferring to eliminate one risk completely over a larger reduction in total risk.

Risk, loss & regretFamily 1301Cognitive biasslide 211 (opens in a new tab)
Zero-sum thinking

We read a situation as a fixed pie, where any gain to one side must be a loss to the other.

Risk, loss & regretFamily 1301Cognitive biasslide 219 (opens in a new tab)

Nearby

The other glossaries, and the guides behind this one

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