Sophistry
No. 02 Cognitive bias

Anchoring

Let the first number you see shape every judgement that follows, even when it's arbitrary.

A graduated scale carrying one tall marker far to the left and a cluster of later readings crowded up beside it. b a c
FIG. 2a, the first number seen, set well off the true value. b, the judgements made afterwards, crowded up against it. c, the reading an independent estimate gives, drawn dashed because nobody made it.

Illustrative example

A jacket marked "was £300, now £120" feels like a bargain, even if £120 was always its normal price.

Anchoring is the tendency to judge later numbers relative to the first one you saw, even when that first number has no real connection to the true value.

Retailers use this constantly: a crossed-out “original” price sets the anchor, making the sale price feel like a discount regardless of what the item is actually worth.

Before judging whether a number is good or bad, ask what it would look like with no anchor at all, based on independent information.

Seen in the wild

Real, sourced instances of this technique in actual public debate.

Examples are chosen for how clearly they show the technique, not for who said it.

Boris Johnson

Leans right

Foreign Secretary; formerly a leading figure in the Vote Leave campaign

Read together
The number, restated a year after the vote

“once we have settled our accounts, we will take back control of roughly £350 million per week.”

September 15, 2017 (Daily Telegraph article)Full Fact, quoting the article; Sir David Norgrove's reply of September 17, 2017 is published in full by the UK Statistics Authority (opens on the source site)

WatchJohnson standing by the figure on Good Morning Britain (opens on the site hosting the footage)
The number raised, not dropped

“There was an error on the side of the bus. We grossly underestimated the sum over which we would be able to take back control.”

January 16, 2018 (interview with the Guardian)The National, quoting the Guardian interview, where he put the figure at £438 million (opens on the source site)

Context
The figure had been the centrepiece of the Vote Leave campaign bus. It is a gross number: it counts the UK rebate, which is never actually sent, and ignores the money the EU pays back to the UK for farming and research. Two days after this article the UK Statistics Authority wrote to Johnson calling it "a clear misuse of official statistics".
Reading
Watch what the second quote does. The figure had just been called a misuse of official statistics, and the answer was not to drop it but to raise it. That only works because the number had already done its job: by then the argument was about how big the weekly sum is, not whether a weekly gross transfer is the right way to describe what EU membership costs. Anyone who replies "it is really £250 million" has accepted the frame and is now haggling inside it. That is what an anchor is for, and it is why the correct figure never catches up with the first one.

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