persuasion
Sunk cost fallacy vs loss aversion
What's the difference between the sunk cost fallacy and loss aversion?
Loss aversion is the tendency for losses to feel worse than equivalent gains feel good. The sunk cost fallacy is one error that this bias can lead you into: continuing with something just because quitting would mean acknowledging what you’ve already spent is gone. One is the bias; the other is the mistake it can cause.
Also known as: loss aversion vs sunk cost
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The demo
Same family, different beast. Read each situation and decide which one is at work - then see whether the deciding factor sits in the future or the past.
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You'd feel worse losing £20 than you'd feel good finding £20.
Loss aversion - a straight comparison of a loss against an equal gain, with nothing yet spent. The loss simply looms larger.
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You sit through a film you're not enjoying because you paid for the ticket.
Sunk cost - the ticket money is already gone whether you stay or leave, yet it's the very thing keeping you in your seat.
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You keep an expensive gym membership you never use, because cancelling would admit it was wasted.
Sunk cost - the past payments are unrecoverable, but you keep paying to avoid facing them as a loss.
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Offered a coin-flip to win £150 or lose £100, you decline despite the favourable odds.
Loss aversion - nothing has been spent; the possible £100 loss just weighs more than the larger possible gain.
Sort all four. The tell: is the deciding cost still ahead of you, or already behind you?
What this demo shows (text version)
Four situations are sorted into "loss aversion" or "sunk cost". Two are loss aversion: dreading a £20 loss more than enjoying a £20 gain, and declining a favourable coin-flip - both weigh a loss that has not happened yet. Two are sunk cost: finishing an unenjoyable film because the ticket is paid for, and keeping an unused gym membership - both honour money already spent and unrecoverable.
The distinction is direction in time. Loss aversion is the general tendency to weight a prospective loss more heavily than an equal gain. The sunk cost fallacy is the specific error of letting an unrecoverable past cost drive a decision that should turn only on what happens next. Sunk cost is loss aversion aimed backwards.
Loss aversion means losses hurt more than gains feel good; the sunk cost fallacy is one error it can push you into - sticking with something because quitting means admitting what you’ve already spent is gone. One looks ahead at a loss you might still avoid; the other looks back at one you can’t undo. You can see and try this concept in action on this page.
Sorting the cases, you could feel the line between them: loss aversion weighs a loss you might still take; sunk cost clings to one you already took and cannot undo. Mix them up and you reach for the wrong fix.
The quick test is direction in time. Loss aversion looks forward - it overweights a prospective loss you could still avoid. Sunk cost looks back - it drags in money, time or effort that is already gone whatever you decide. Sunk cost is loss aversion pointed at the past.
They turn up together, which is why they blur: you keep funding the failing project (sunk cost) partly because writing it off would crystallise a loss you are averse to feeling (loss aversion). Naming which part is which tells you what to do - ignore what is already spent, and judge only the choice still ahead.