The Option You Were Never Meant to Buy

Next time you buy popcorn, look properly at the sizes. Say a small for three pounds, a large for seven, and wedged between them a medium for six pounds fifty. Fifty pence less than the large, for a good deal less popcorn. The exact prices vary; the shape is familiar. You will not think about it for long. You reach for the large, feeling like you spotted a bargain.

You have not spotted anything. The large looks like a bargain because the medium is sitting beside it. The medium does not need many buyers to matter: beside the large it loses the comparison, and in losing makes the large look like the obvious, thrifty choice. It can sell almost none of itself and still change what gets bought.

To see why that works, notice how you judge a price. You do not weigh it against some settled sense of what popcorn is worth. Nobody carries a true price in their head. You judge it against the other numbers in front of you. And that is the opening. Whoever sets the board controls what each option gets compared against. You can shift how good a thing looks without altering the thing itself, only what sits beside it.

The most famous demonstration used prices The Economist once listed. Offered a web subscription for fifty-nine dollars and a print-and-web bundle for a hundred and twenty-five, most people take the cheaper web one. Add a third option, print alone at a hundred and twenty-five, the same price as the bundle that throws in the web edition for nothing extra, and the choice flips. That useless third option changes the whole comparison: the great majority now take the bundle, because beside it a hundred and twenty-five dollars looks like a gift.¹ One option nobody chose changed what almost everybody chose.

The dominated decoy is only the cleanest version. A comparison can be shaped in other ways. Set one option far pricier than the rest and it drags your sense of normal upward, so the one beneath it reads as sensible. Offer three tiers and the middle can gain simply by being neither extreme. Different mechanisms, one shared privilege: whoever chooses the alternatives chooses the comparisons you make. The set is the argument, and someone else wrote it. The pull goes deeper still. Often you have no finished preference when you begin, and the set becomes your yardstick, what counts as dear, what counts as generous, before you have judged anything at all.²

None of this is a spell. The decoy effect itself is real but modest, and it comes and goes. It has proved most reliable in the kind of choice the Economist offered, where every option is a tidy number and the comparison is easy to run in your head. Give people messier, more realistic options, and it becomes much less dependable. In a study of millions of supermarket wine purchases, the presence of a dominated decoy was associated with a small shift toward the target, and least of all among the shoppers who bought wine most often.³ Experience seems to blunt it.

Once you have the shape, you see it well past the shop. A hiring shortlist with one candidate clearly weaker than your favourite, so the favourite reads as the obvious call. A house shown first, tired and overpriced, so the next one arrives as relief. And the version that should trouble anyone who reads a chart: a new system announced at eighty-seven, sat beside an old baseline at fifty-four, so the eighty-seven lands like a triumph. Put the real rival back, an existing system quietly scoring eighty-two, and the triumph shrinks to the five points it always was. Nothing about the new system changed. The set it was measured against did.

A weak baseline is a decoy with a chart around it. A field can flatter a winner two ways, by adding something weak or by leaving out something strong. The baseline at fifty-four matters less than the rival at eighty-two you were never shown. When a result looks unusually good, look hard at what it beat, then ask what should have been in the field and was not.

A menu is sometimes just a menu, and an inferior option can survive for reasons that have nothing to do with persuasion: legacy pricing, a segment you are not in, plain incompetence. The tell to watch for is an option plainly worse than another for the same money, or the same money for plainly less. Finding one does not prove someone planted it, but it is a good reason to inspect the comparison it creates. The options around a thing can carry real information; the mistake is letting someone else’s set become your standard without noticing.

The test takes about ten seconds. Strike out the option that makes your choice look good, and ask whether you would still want what you wanted. Then ask what is missing. Would you still choose it beside the rival you would really buy, the house you could actually afford, or the number it truly has to beat? And does it still make sense against what you need and can spend? If your choice survives that, it survived the comparison. If it weakens, part of what impressed you belonged to the field, not the winner. Most choices still need comparison, so do not stop comparing. Choose the comparison yourself.

The board was built to be read across, each option lending meaning to the next. The comparator is part of the claim: a winner is only as impressive as the field it was allowed to beat. Before you trust one, look hard at that field, and ask whether it still wins in the set you would have chosen.

The option you were never meant to buy is the one doing the selling.

Footnotes

1. The pricing came from a real Economist subscription page; the choices were measured by Dan Ariely in Predictably Irrational (HarperCollins, 2008), chapter 1. Offered all three options, about 100 students split 16 for web-only, none for print-only, and 84 for the print-and-web bundle. With the print-only option removed, the same offer drew 68 for web-only and 32 for the bundle. ↩

2. People often do not arrive with settled preferences waiting to be revealed. They build them while choosing, from the options in front of them and the way the choice is framed: Bettman, Luce and Payne, “Constructive Consumer Choice Processes” (Journal of Consumer Research, 1998). ↩

3. The pull is strongest in stylised, all-numbers choices like the Economist’s and weakens with realistic options: Frederick, Lee and Baskin, “The Limits of Attraction” (Journal of Marketing Research, 2014). In a study of 3.6 million UK supermarket wine purchases, a dominated decoy shifted preference toward the target by roughly one per cent overall, and least of all for the shoppers who bought wine most often: Devine, Goulding, Harvey, Skatova and Otto, “How decoy options ferment choice biases in real-world consumer decision-making” (npj Science of Learning, 2025). ↩