Anchors

Kahneman describes anchoring, one of the most robust and surprising effects in psychology: when people consider a particular number before estimating an unknown quantity, their estimate is pulled toward that number — even when the number is plainly arbitrary and irrelevant. The anchor sets a reference point that the final judgment never fully escapes, and the pull operates whether or not the person is aware of it and whether or not they believe themselves influenced.

Kahneman and Tversky's classic demonstration used a wheel of fortune secretly rigged to stop on either 10 or 65. After watching the wheel, participants estimated the percentage of African nations in the United Nations. Those who saw 65 gave far higher estimates than those who saw 10 — an obviously random number had moved their judgment of an unrelated fact. The effect appears everywhere: asking whether Gandhi was older or younger than 144 when he died produces higher age estimates than anchoring on 35.

Kahneman identifies two distinct mechanisms behind the single effect. One is deliberate adjustment, a System 2 process: starting from the anchor and adjusting away from it, but typically stopping too soon, so the estimate stays biased toward the anchor. The other is associative priming, a System 1 process: the anchor activates compatible evidence and associations, biasing the whole interpretation before any conscious adjustment begins. Both push in the same direction, which is why anchoring is so powerful and so hard to resist.

The reach of anchoring into real decisions is considerable. Real-estate professionals shown a house with different arbitrary listing prices produced appraisals that tracked the list price — while confidently denying that the number had influenced their expert judgment. Anchors shape negotiations, where the first offer sets the frame; they shape sentencing, donations, and purchasing, where suggested amounts pull actual choices. The anchoring index measures the effect's strength, and it is frequently large, often around fifty percent of the distance between anchors.

The applied takeaway is to recognize anchors and, where possible, neutralize them. In a negotiation, the first number stated exerts a gravitational pull, so being deliberate about who anchors and at what value is strategically decisive; when facing an anchor you consider extreme, the counter is to actively generate arguments against it rather than merely adjusting from it. Awareness alone is a weak defense — experts who knew about anchoring were still moved by it — so the practical guard is to question whether an arbitrary number has seeped into your estimate.

Kahneman's deeper point is that anchoring exposes how thoroughly our judgments are constructed rather than retrieved. We feel we are reading a value off some inner gauge, but the gauge is reset by whatever number happened to be in view a moment earlier. This susceptibility to irrelevant reference points is not a quirk of the unintelligent; it is a structural feature of how the mind builds estimates, and it reveals the unsettling extent to which our 'considered' numerical judgments are at the mercy of context.