Anchoring.
The first number you see pulls your guess toward it.
A number you see first, even a random one, can pull the estimate you make next. In replications it was two to three times stronger for factual guesses, very weak for everyday prices, and on simple gambles there was none.
25 vs 45
Median guesses, in percent, at the share of United Nations countries that are African, after a rigged wheel landed on 10 or on 65.
The evidence for this splits.
Also under Beliefs.
Tversky & Kahneman 1974 · Klein et al. 2014 (Many Labs) · Fudenberg, Levine & Maniadis 2012