Cognitive bias
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Part of:Decisions without regret →
All fallacies and biasesCognitive biases list
The planning fallacy is underestimating the time, cost, or difficulty of a task, especially one you are inside. You picture the smooth path and leave out delays that, on similar tasks, usually appear. Hope is not a base rate.
Planning fallacy is filed here as a bias. If you cannot point to that move in the remark in front of you, you do not yet have this bias. Disliking the conclusion is not enough, and a true premise does not repair a broken step.
This page adds no new definition and no statistic. The three scenes below only move the library’s example into a meeting, a news sentence, and a social feed. None of them is a reported case, and none of them carries a number.
The library’s example is the anchor, quoted so the later scenes cannot drift: “You plan to finish the essay in an evening because that is how the writing feels at the desk. Your last four essays each took three evenings.” The three that follow change the room and keep the step.
Picture that example in a meeting, aimed at someone who has to answer before the next item. If the room cannot give the reply on the card, it has not answered the point. It has used Planning fallacy. No survey of offices is claimed. The test is whether the step matches the card.
The same step can sit in a speech or a headline, where the pause is shorter and the audience is larger. Imagine the stored example said into a microphone and left unpacked. This is not a claim about a particular broadcast or a particular paper. The correction is still the reply on the card, not a different theory of the press.
Imagine the example as a caption. Agreement is not evidence the step was valid, and outrage is not evidence a different bias was in play. Match the step to the definition before you name it.
Look up how long similar tasks actually took, including the ones that slipped. Add the ordinary interruptions before you believe the optimistic path.
“That is Planning fallacy” is not yet an answer. Name the step, then ask the question the card tells you to ask. If the remark survives, drop the label. If it fails, you still owe a reason for what you think instead. The reply does not hand you a new conclusion.
Planning fallacy is easy to shout in place of a neighbour. The nearest card people mix this up with is Anchoring. Use the comparison linked under this section when you are unsure which name fits. The comparison quotes the cards. It does not invent a third definition.
Write down the sentence you think is the mistake. If it matches one definition, use that name. If it matches neither, do not force a label. If it matches both, answer the two steps separately.
You plan one evening for an essay, though your last four each took three. What is this?
The options and the explanation open in the quiz. Scoring stays on this device. There is no pass mark on this card.
The planning fallacy is underestimating the time, cost, or difficulty of a task, especially one you are inside. You picture the smooth path and leave out delays that, on similar tasks, usually appear. Hope is not a base rate.
You plan to finish the essay in an evening because that is how the writing feels at the desk. Your last four essays each took three evenings.
Look up how long similar tasks actually took, including the ones that slipped. Add the ordinary interruptions before you believe the optimistic path.