Anchoring: The First Number Wins

01The Pull of the First Number

In a classic experiment, Amos Tversky and Daniel Kahneman asked participants to spin a rigged wheel — it always landed on either 10 or 65 — then estimate the percentage of African nations in the United Nations. People who saw 65 guessed far higher than those who saw 10. The wheel was obviously random. It didn't matter. The number lodged, and judgment bent toward it.

This is anchoring: the tendency for an initial piece of numerical information to pull subsequent estimates in its direction, even when that information is irrelevant, arbitrary, or known to be wrong. It is one of the most robust findings in behavioural science — replicated across cultures, professions, and stakes — and it operates largely outside conscious awareness.

The mechanism is still debated. One account, favoured by Tversky and Kahneman, frames anchoring as insufficient adjustment: people start from the anchor and move, but they don't move far enough. A second account, developed by Thomas Mussweiler, Fritz Strack and colleagues, emphasises selective accessibility — the anchor primes information consistent with it, making anchor-confirming evidence easier to retrieve. Both processes probably contribute, which is part of why anchoring is so hard to escape.

The wheel was obviously random. It didn’t matter.

02Where It Shows Up

The applied consequences are everywhere. In salary negotiation, whoever states a number first tends to set the range; counteroffers cluster around the opening figure rather than some independent assessment of worth. In retail, a crossed-out "original price" anchors the perceived value of whatever is actually being charged. In legal sentencing research, judges given higher recommended sentences have been found to hand down longer terms — even when the recommendation came from a randomised source.

Real-estate agents shown houses with inflated list prices rate them as worth more than identical properties with lower asking prices. Medical professionals are not immune: exposure to an initial (sometimes incorrect) test result or diagnosis shapes subsequent clinical reasoning in demonstrable ways.

Awareness of the bias helps only modestly. Knowing anchoring exists does not reliably neutralise it; deliberate counter-adjustment tends to undershoot. What does work, in practical settings, is generating your own independent reference point before encountering anyone else's number — or seeking outside data that establishes a credible alternative anchor. In negotiation, making the first offer can be an advantage precisely because it sets that anchor; so can explicitly labelling an anchor as extreme and arguing against it, which appears to partially reduce its grip.

The evidence rating here is strong. Anchoring is not a lab curiosity; it is a standing feature of numerical judgment wherever first figures are encountered.