Abstract

Class inclusion, the conjunction fallacy, and other phenomena are presented to illustrate cognitive illusions, that reasoning can be misdirected so that errors of judgment violate known principles. Errors in class inclusion are traced to accessing and implementing logical knowledge, rather than logical deficits, memory overload, or misleading questions. It is argued that superordinate-set cuing does not afford subset comparisons, but, rather, facilitates implementation of logical knowledge. According to fuzzy-trace theory, successful performance involves applying the cardinality principle, but also suppressing solutions based on judgments of relative numerosity, in which horizontal relationships between classes are apt to usurp the role of vertical ones