People can size up a person or situation in seconds and successfully act on that judgment. This instant assessment of people and things—snap judgments, intuition, pattern recognition, simple common sense—is a natural part of the human nervous system, which can do almost instantly what it would take an expert days or weeks to deduce through logic and reasoning.

Somehow, the mind reaches into its vast store of knowledge and experience acquired over many years, and effortlessly pulls out the right answer to a given situation. Instead, when people try to solve a situation by carefully thinking it through, they wind up making bad decisions. Their first instinct, which they ignore, turns out to be the better answer.

This flies in the face of Western philosophy, namely, that the more information people have and the more thinking they do, the better responses will be. In fact, more information often makes judgments worse—not better.

Fast-and-frugal thinking proves especially helpful in cases where a situation is changing quickly—say, during an emergency—or when one must make important decisions in a very short time. 

Quick responses sometimes can go amiss. It may be assumed, on meeting someone, that they possess traits believed common to members of their race or sex or age group, when in fact none of those aspects is true.