Sunk Cost Fallacy
What it is
Encouraging continued investment by emphasizing what has already been spent.
How it works
Real-world examples
- •"You've already put in six months, don't quit now" at a bad job.
- •Continuing to watch a terrible movie because you paid for the ticket.
- •Staying in a failing business partnership because of the initial capital invested.
Ethical guidelines
- ●Help people make forward-looking decisions, not backward-looking ones.
- ●Do not guilt people into continuing based solely on past investment.
- ●Frame choices in terms of future value, not sunk costs.
How to defend against it
- ►Ask: "If I were starting fresh today, would I make this choice?"
- ►Accept that past costs are gone regardless of your next decision.
- ►Focus on future costs and benefits, not what has already been spent.
From the Defense Playbook
When you want to help someone reconsider a belief or a habit, stop arguing for the change and instead draw out their own reasons for and against it, because people are persuaded by what they hear themselves say and push back against what they are told.
Many jurisdictions give you a legal right to cancel certain purchases within days of signing, with no reason required, precisely because those sales settings are built for pressure; know which sales are covered, and cancel in writing inside the window.
At the moment you start any trial, introductory rate, or auto-renewing contract, put a reminder in your calendar a few days before it renews, with the cancellation link and the price it will jump to, because the business model counts on you forgetting.
Every playbook entry states how strong its evidence is and when not to use it. Browse the full playbook.
References
- Arkes, H. R., & Blumer, C. (1985). The psychology of sunk cost. Organizational Behavior and Human Decision Processes, 35(1), 124–140 · linkFoundational empirical treatment showing prior investment (sunk cost) irrationally influences continued commitment.