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Sunk Cost Fallacy

Also Known As: Concorde Fallacy Escalation of Commitment Throwing Good Money After Bad
Cognitive Bias ID: sunk_cost_fallacy

Definition

The sunk cost fallacy is the tendency to continue investing time, money, or effort into a project or decision because of what has already been invested, rather than evaluating the decision based on future costs and benefits. Rational decision-making should only consider prospective costs and benefits, but people feel compelled to 'justify' past investments by continuing.

Examples

A company continues developing a software product that market research shows customers do not want, because they have already spent two years and $5 million on it, reasoning that stopping now would 'waste' the investment.

A couple continues attending weekly couples therapy sessions they both privately agree are not helping, because they have already paid for and attended 20 sessions — telling themselves it would be a 'waste' to stop now rather than trying a different therapist or approach.

A student who dislikes their chosen university major and has poor grades in it refuses to switch fields in their second year, reasoning that they have already completed two semesters of coursework in it and cannot 'throw that away,' even though switching now would still leave three years to build a fulfilling career in something they enjoy.

Verification Steps
Verification Steps
Binary yes/no questions that an AI must answer to detect a reasoning pattern in a text.
Each of the 452 aspects has verification steps — simple yes/no questions designed to systematically detect whether a pattern appears in a text. For ad hominem: "Does the argument attack a person rather than their claim?" For false dichotomy: "Are only two options presented when more exist?" This ensures consistent, reproducible analysis.

Binary (yes/no) questions an LLM must answer to identify this aspect:

  1. 1

    Has a significant investment (time, money, emotion) already been made?

    Type: binary
  2. 2

    Is the decision to continue based primarily on the past investment rather than future prospects?

    Type: binary
  3. 3

    Would a rational analysis (ignoring past costs) favor a different decision?

    Type: binary
Deep Dive
The expandable detail section on each aspect page with examples, psychology, and counter-strategies.
The Deep Dive section provides in-depth information about each aspect: a real-world example showing the pattern in action, an explanation of why it works psychologically, practical advice on how to counter it, alternative names, and links to related aspects.

Hierarchical Context