The First Number Said Out Loud Anchors Everything After
By Amanuel Bekele · The Science of Persuasion
In 1974, Amos Tversky and Daniel Kahneman described an experiment that became one of the most-cited findings in behavioural science.1 Participants watched a wheel of fortune, rigged to stop at either 10 or 65. Then they were asked two questions: was the percentage of African countries in the United Nations higher or lower than that number, and what was their own estimate?
The wheel had no possible connection to the question, and everyone had just watched it spin. Yet the group who saw 10 gave a median estimate of 25%. The group who saw 65 gave 45%. A number everyone knew was meaningless pulled their judgement towards it.
How anchoring works
Tversky and Kahneman called this anchoring and adjustment. Once a number enters a judgement, people adjust from it rather than starting fresh, and the adjustment is usually too small. The final estimate stays skewed towards wherever it began.
Later work explained part of the mechanism. When you consider whether an answer is close to a given number, you search your memory for reasons it might be, and those reasons stay at hand when you form your own estimate.2 In one study, people asked whether Gandhi died before or after the age of 140, an absurd anchor, still gave higher estimates of his age at death than people asked about the age of 9. An anchor does not have to be plausible to work.
Experts are not immune
It is tempting to think anchoring only catches people guessing outside their field. The research says otherwise.
In a 1987 study, real estate agents toured a house and were given a property information sheet with a listing price that was varied between groups.3 Their appraisals moved with the listing price. The agents mostly said the listing price had not influenced them; amateurs given the same task were more willing to admit it had.
In 2006, experienced legal professionals read a criminal case and were given a prosecutor's sentencing demand determined, openly, by the roll of a pair of dice.4 Those who saw a higher roll gave longer sentences. Expertise reduced their uncertainty about the case. It did not protect them from the number.
The first offer in a negotiation
Adam Galinsky and Thomas Mussweiler took the finding into negotiation.5 In their studies, whichever side made the first offer tended to get a better outcome, because the first offer anchored the rest of the bargaining around it. The opening number did not need to be better informed. It just had to come first.
They also found a defence. When the side receiving the first offer focused on information that contradicted it, such as the other party's walk-away point or their own alternatives, the first-offer advantage disappeared.
Awareness alone doesn't fix it
The uncomfortable part of the original finding is that participants knew the number was random. They had just seen it generated. Knowing an anchor is arbitrary reduces its pull a little, but does not remove it.
What works better is deliberately generating reasons the anchor could be wrong. In a study by Mussweiler, Fritz Strack and Tim Pfeiffer, people asked to consider arguments against an anchor's value showed a much smaller anchoring effect.6 The bias works by making anchor-consistent evidence easy to find, so the correction is to go looking for the other kind.
Why this matters the moment you say a number out loud
In a pitch, a negotiation, a budget meeting or any talk where a figure is stated (a price, a timeline, a target), the first number spoken sets the range the rest of the conversation is judged against, whether or not it was carefully chosen.
"This would normally cost $50,000" said before "we're offering it for $12,000" does more than inform. It sets the frame the second number is judged inside. "It could take up to a year" said before "we think six months" makes six months sound fast.
Using it honestly
The number you choose to say first, and whether you say one before the audience forms their own estimate, is a real point of leverage. Used carelessly or dishonestly, it is a real point of manipulation. Some practical guidance on the honest side of that line:
- Choose your first figure on purpose. If you will give a range, the number you say first frames the rest. Lead with the one you can defend.
- Make sure the anchor is true. A comparison price nobody ever paid is a manipulation, and audiences who discover it stop trusting the rest of your figures.
- Give context with the number. "Twelve weeks, which is about half the industry norm" helps the audience judge the figure, rather than leaving the first number they heard to do it for them.
- Watch for anchors aimed at you. When someone opens with a figure, before you respond, list the reasons it might be too high or too low. Then name your own number, built from your own reasoning.
The research does not tell you which side of the line you are on. It tells you the line exists, and that the first number matters more than it feels like it should.
References
- Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: heuristics and biases. Science, 185(4157), 1124–1131. https://doi.org/10.1126/science.185.4157.1124
- Strack, F., & Mussweiler, T. (1997). Explaining the enigmatic anchoring effect: Mechanisms of selective accessibility. Journal of Personality and Social Psychology, 73(3), 437–446. https://doi.org/10.1037/0022-3514.73.3.437
- Northcraft, G. B., & Neale, M. A. (1987). Experts, amateurs, and real estate: An anchoring-and-adjustment perspective on property pricing decisions. Organizational Behavior and Human Decision Processes, 39(1), 84–97. https://doi.org/10.1016/0749-5978(87)90046-X
- Englich, B., Mussweiler, T., & Strack, F. (2006). Playing Dice With Criminal Sentences: The Influence of Irrelevant Anchors on Experts’ Judicial Decision Making. Personality and Social Psychology Bulletin, 32(2), 188–200. https://doi.org/10.1177/0146167205282152
- Galinsky, A. D., & Mussweiler, T. (2001). First offers as anchors: the role of perspective-taking and negotiator focus. Journal of Personality and Social Psychology, 81(4), 657–669. https://doi.org/10.1037/0022-3514.81.4.657
- Mussweiler, T., Strack, F., & Pfeiffer, T. (2000). Overcoming the Inevitable Anchoring Effect: Considering the Opposite Compensates for Selective Accessibility. Personality and Social Psychology Bulletin, 26(9), 1142–1150. https://doi.org/10.1177/01461672002611010