Cjep 59-1

A well-established finding in research on concepts and categories is that some members are rated as better or more typical examples than others. It is generally thought that typicality reflects centrality, that is, that typical examples are those that are similar to many other members of the category. This interpretation of typicality is based on studies in which participants had little knowledge about the relevant categories. In the present study, experienced fishermen were asked to give goodness-of-example ratings to familiar freshwater fish. These fishermen were of two cultural groups with somewhat different goals and ideals. Typicality was well predicted by fishes’ desirability and poorly predicted by their centrality. Further, the two cultural groups differed in their typicality ratings in ways that corresponded to their different goals and ideals. For knowledgeable reasoners typicality in natural taxonomic categories appears based on ideals rather than on centrality. The psychology of concepts and categories has seen a great deal of progress over the past several decades (see Murphy, 2002 and Wisniewski, 2002 for recent reviews). Much of the impetus for a resurgence of interest in categorization came from studies by Rosch and her associates (e.g., Rosch & Mervis, 1975; Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976) on the structure of natural object categories and by Brooks (1978; see also Jacoby & Brooks, 1984) on the roles of different kinds of processing (e.g., analytic versus nonanalytic) in category formation and representation. Although the field’s overall progress has been undeniable, it has also been uneven, and sometimes researchers have been criticized for focusing so much on a single task that they end up learning more and more about less and less (e.g., Murphy, 2003). One antidote for insularity is to build bridges between lab and field research by studying populations of participants who have relevant knowledge and expertise in some content domain (e.g., Johnson & Mervis, 1998; Medin & Atran, 2004; Norman, Brooks, Coblentz, & Babcook, 1992; Norman et al., 1996). This can yield a two-way benefit, as measurement tools developed with the standard population of college undergraduates inform studies of other populations, and, in turn, studies of groups with relevant knowledge raise methodological and conceptual issues that feed back into new theory and data in the lab (e.g., Brooks, LeBlanc, & Norman, 2000). The present research concerns one of the most basic empirical phenomena in categorization: typicality, or goodness of example. Not only is it the case that some instances of a category are rated as better examples than others, but also there is strong evidence that the underlying basis for typicality is centrality with respect to the category’s features (Rosch & Mervis, 1975): It has often been found that good examples of a category tend to share features with other category members and to not share features with members of contrasting categories. For example, cardinals are often judged as better members of the category BIRD than are penguins, and feature-listing tasks with the same populations of participants show that cardinals have more categorytypical properties (e.g., singing, flying, building nests in trees) than do penguins. The notion that typicality is determined by centrality has a long history of empirical support, but it comes from studies that have certain limitations. First, studies of typicality have often used artificial categories (e.g., Medin & Schaffer, 1978). This allows experimental control of category structure but almost ensures that the stimuli will not be meaningful to participants (see Murphy & Allopenna, 1994, for an exception). Second, when studies have involved natural taxonomic categories (e.g., Rosch et al., 1976), the participants (undergraduates) generally have had little relevant knowledge about them. To move beyond these limitations, one can either use more expert participants or use categories of a different sort. In either case the results seem to take a different form. Barsalou (1985) showed that typicality effects for goal-derived categories are driven by proxRussell C. Burnett and Douglas L. Medin, Northwestern University Norbert O. Ross, Vanderbilt University Sergey V. Blok, Northwestern University Canadian Journal of Experimental Psychology, 2005, 59-1, 3-10 CJEP 59-1 2/10/05 4:42 PM Page 3