A heuristic is a simple thinking strategy that allows people to make judgments and solve problems efficiently. It is a mental shortcut that usually works well enough, even if it does not guarantee a correct answer.

The availability heuristic judges probability by the ease with which examples come to mind. The representativeness heuristic judges probability by how well something matches a prototype. The anchoring heuristic adjusts estimates from an initial value that may be arbitrary. These shortcuts save time and effort, yet they produce systematic biases when the structure of the environment does not match the heuristic’s assumptions.

Heuristics are not the opposite of rational thought. They are adaptations to limited time, limited information, and limited computational capacity. Experts develop domain-specific heuristics that are highly accurate within their field. The study of heuristics and biases, pioneered by Kahneman and Tversky, has mapped both the power and the pitfalls of these everyday strategies.

When a quick answer is needed and a perfect analysis is impossible, a heuristic is often the tool that is used.