You’re 45 minutes into a terrible movie. You know it’s not getting better. You stay anyway.
You’ve already paid. Leaving feels like waste. So you spend another 75 minutes being miserable — to avoid losing something you’ve already lost.
That’s the Sunk Cost Fallacy.
What Is the Sunk Cost Fallacy?
The Sunk Cost Fallacy is the tendency to continue an endeavour because of previously invested resources — time, money, or effort — that cannot be recovered, even when continuing is clearly the worse choice.
A sunk cost is any past investment that is gone regardless of what you do next. The $15 movie ticket is spent whether you leave at minute 45 or stay until the credits. The rational decision should only consider future costs and benefits. The fallacy is letting the irretrievable past change your future.
The Psychology Behind It
Loss aversion drives the Sunk Cost Fallacy. Psychologists Kahneman and Tversky demonstrated that losses feel roughly twice as painful as equivalent gains feel good. When we’ve invested in something, abandoning it activates the pain of loss — even when cutting losses is the correct move.
There’s also a social dimension: we don’t want to appear wasteful or admit we were wrong. Staying the course can feel like loyalty or persistence. Leaving feels like failure.
Real-World Examples
The bad job. “I’ve already been here four years. I can’t leave now.” The four years are gone. The only question is whether the next year will be better spent here or elsewhere.
The losing investment. “I can’t sell now — I’d be selling at a loss.” But the loss already happened when the price fell. Holding a bad investment because of its purchase price is the fallacy in pure form. The market doesn’t know or care what you paid.
Business projects. Companies routinely pour money into failing projects because they’ve “already spent so much.” The $50 million already spent is irrelevant to whether spending another $10 million is a good idea. Only the future return matters.
Relationships. “We’ve been together seven years. I can’t walk away from that.” Seven years of shared history is meaningful context — but it’s not a reason to continue a relationship that is making both people miserable.
The Concorde effect. The British and French governments continued funding the Concorde supersonic aircraft for years after it became clear the project would never be commercially viable. They had invested too much to stop. Economists now call this “Concorde fallacy.”
The Correct Question
The antidote is a single question: “If I had not already invested X, what would I choose now?”
Strip out the history. Evaluate the future on its own terms. If the honest answer is “I wouldn’t continue” — then continuing is the fallacy.
This is harder than it sounds. We are wired to feel the weight of past investment. The trick is to practise noticing when past costs are entering your reasoning about future choices, and then deliberately excluding them.
When Persistence Is Right
It’s worth distinguishing the Sunk Cost Fallacy from legitimate persistence. Not every instinct to continue is a fallacy. Sometimes the correct analysis of future costs and benefits genuinely favours continuing — even after significant losses. The fallacy is specifically when past investment is the primary reason to continue, not a genuine assessment of future value.
Can You Spot It in Context?
The Sunk Cost Fallacy appears as a scenario in Mind Traps — a free 40-level psychology quiz. Many players confuse it with the Ratchet Effect or the IKEA Effect. The scenarios make the differences clear.
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