The Guppy Effect as Interference

A concrete formal understanding of how concepts combine is vital to significant progress in many fields including psychology, linguistics, and cognitive science. However, concepts have been resistant to mathematical description because people use conjunctions and disjunctions of concepts in ways that violate the rules of classical logic; i.e., concepts interact in ways that are non-compositional [4]. This is true also with respect to properties (e.g., although people do not rate talks as a characteristic property of Pet or Bird, they rate it as characteristic of Pet Bird) and exemplar typicalities (e.g., although people do not rate Guppy as a typical Pet, nor a typical Fish, they rate it as a highly typical Pet Fish [5]). This has come to be known as the Pet Fish Problem, and the general phenomenon wherein the typicality of an exemplar for a conjunctively combined concept is greater than that for either of the constituent concepts has come to be called the Guppy Effect, although further investigation revealed that the Pet Fish Problem is not a particularly good example of the Guppy Effect, and that other concept combinations exhibit this effect more strongly [6]. One can refer to the situation wherein people estimate the typicality of an exemplar of the concept combination as more extreme than it is for one of the constituent concepts in a conjunctive combination as overextension.