In the mid 1970s, Rosch discovered that categories are not defined by a set of list of necessary and distinctive features that all members share, but are constructed around best examples or prototypes. For this reason, people can rank items in terms of their goodness as examples of a given category. Prototypes and default values provide many abstract schemas with extremely rich content. Unpacking the schemas that underlie even a small piece of discourse can be a very complex process. Reasoning also involves the opportunistic and imaginative extension of cognitive schemas to the novel situations that one confronts through metaphor .
Examples are ubiquitous.
We metaphorically extend this schema to a wide variety of concepts and events that do not have any literal boundaries, and our understanding of these concepts and events is grounded in these metaphorical extensions. At this point, one may get the impression that schema theorists hold the view that the creation of schemas, and the extension of them through metaphor, is something that occurs entirely in the heads of individual human beings. While computational modelers and psychologists have focused primarily on the individual as the unit of analysis for understanding the development of schemas, anthropologists and linguists have focused on immense role that culture plays in the development of widely shared schemas that are transmitted across people and through generations. One can also look at a particular metaphor as something that evolves in a particular cultural context, and which becomes strongly embedded in the language that people use to communicate with one another. For this reason, a researcher can gain insight into the motivations underlying a person's behavior by gaining insight into the schemas, and the relationships among the schemas, in terms of which that person interprets the world.