You paid $15 and that is why you went, not desire

Hal Arkes and Catherine Blumer, two American psychologists, set the experiment up at the box office of a university theatre in Ohio in 1985. Sixty people buying a season ticket were charged different prices without being told: fifteen dollars, the normal price; thirteen, with a small discount; eight, with a large one. The discount was handed out at random, so the three groups were identical in their taste for theatre, in money and in enthusiasm.

Then the stubs were counted. Over the first half of the season, the people who had paid the full fifteen dollars went to more performances than the other two groups. They did not like theatre more. What they had handed over hurt more.

And here is the part almost nobody tells: in the second half the difference had vanished. Money already spent pushes for a few weeks and then runs out of spring.

That is the sunk cost, and it lives in very ordinary things: a membership, a course, a ticket that is no longer refundable, a dinner you paid for in advance. Tomorrow, when you are about to go to something only because you have already paid for it, ask yourself the one question that separates the spending from the decision: if someone had given me that ticket this morning, would I go? If the answer is no, stay at home. The money does not come back by going.