Anchoring

In Nudge: Improving Decisions About Health, Wealth, and Happiness Anchoring is a cognitive bias wherein one relies too heavily on one trait or piece of information. An example would be a resident of Chicago who is asked to guess the population of Milwaukee. Knowing that Milwaukee is a major city, but certainly not as large as Chicago, the person would take the population of Chicago (roughly 3 million) and divide it by, say, three (arriving at one million). A resident of Green Bay (which has a population of around 100,000) might know that Milwaukee is larger than Green Bay, and triple the population of their home city to arrive at a guess (of 300,000). The difference in guesses of people because of their geographical location is an instance of anchoring. The real population of Milwaukee is about 580,000.