What are the odds, from 0 to 100%, that someone will break your heart within the next five years?
How did you answer this question? Maybe you thought about your past relationship experiences, or the person you’re dating right now. Maybe you thought about relevant statistics, like the divorce rate, or the average rate of infidelity. But imagine that just before you read this question, you happened to be checking the weather and saw that the chance of rain tomorrow is 10%. Would that information influence your estimate? What if the chance of rain was 90%?
Arbitrary numbers—referred to by researchers as numerical anchors—can have a surprisingly large impact on people’s judgments.1 We often lack the information we need for the judgments we are asked to make. You might be asked to estimate the length of the Nile river, for example, and find that you can only guess at the answer. To make that judgment, research shows that you are likely to grasp at whatever information you happen to have on hand, even if it’s completely irrelevant. If you’ve recently been looking at the prices of new cars, you might guess that the Nile is shorter than if you’ve recently been looking at the prices of new houses. This phenomenon, known as the anchoring effect, has been demonstrated in hundreds of studies on everything from general knowledge to legal sentencing decisions.