The similarity heuristic.

Abstract

Decision makers are often called on to make snap judgments using fast-and- frugal decisionrules called cognitive heuristics. Although early research into cognitive heuristicsemphasized their limitations, more recent research has focused on their high level ofaccuracy. In this paper we investigate the performance a subset of the representativenessheuristic which we call the similarity heuristic.Decision makers who use it judge the likelihood that an instance is a member of one category rather than another by the degree towhich it is similar to others in that category. We provide a mathematical model of theheuristic and test it experimentally in a trinomial environment. The similarity heuristic turnsout to be a reliable and accurate choice rule and both choice and response time data suggest itis also how choices are made.