What is rational judgement and decision making? One of the classical answer
s to this question has been that judgements and decisions are rational if t
hey conform to the rules of various normative systems such as the probabili
ty theory or expected utility theory. Embedded within this conception of ra
tionality is the fiction that rational agents have unlimited time, knowledg
e, and computational resources for making decisions. However, humans only h
ave limited resources, which is why Herbert Simon conceptualized human rati
onality as "bounded." Boundedly rational decision making does not by any me
ans entail poor performance. We provide examples of computationally simple
heuristics that require little information, yet lead to surprisingly accura
te judgments. The key to their success is ecological rationality, that is,
their adaptation to the information structure of the environments in which
they work.