Incorporating the Irrelevant: Anchors in Judgments of Belief and Value

Imagine walking down a supermarket aisle and passing an end-of-aisle display of canned tomato soup. A sign on the display says, "Limit 12 per customer." Would such a sign influence the number of cans you would buy? Would you buy more cans than if the sign said "No limit per customer"? Our intuitions say no, but empirical evidence indicates that purchase behaviors are influenced by such a sign (Wansink, Kent, & Hoch, 1998). Consider another example: A wheel of fortune is spun and stops at the number 65. You are then asked if the percentage of African countries in the United Nations is above or below that number. Could this exercise influence your estimate of the relevant percentage? Although it may seem unlikely, the evidence is that such anchors have an effect: Groups who received larger numbers determined by a wheel of fortune gave higher estimates than groups who received lower numbers, demonstrating that irrelevant anchors influenced these estimates (Tversky & Kahneman, 1974).