Classification and categorization: a difference that makes a difference

Library Trends, Wntr, 2004 by Elin K. Jacob

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The literature on categorization is riddled with passages where the terms "classification" and "categorization" are used indiscriminately to refer to the same process. Rosch et al. (1976) provides an illustrative example of how these two terms are used indiscriminately:

   ... one purpose of categorization is to reduce the infinite
   differences among stimuli to behaviorally and cognitively usable
   proportions. It is to the organism's advantage not to differentiate
   one stimulus from others when that differentiation is irrelevant for
   the purposes at hand. The basic level of classification, the primary
   level at which cuts are made in the environment, appears to result
   from the combination of these two principles; the basic
   categorization is the most general and inclusive level at which
   categories can delineate real-world correlational structures.
   (Rosch et al., 1976, p. 384. Emphasis added)

This lack of distinction between category/categorization and class/classification is frequently compounded by the use of concept as yet another synonym for category (e.g., Gardner, 1987, p. 340). Unfortunately, this terminological imprecision obscures the fact that researchers are actually dealing with two similar but nonetheless distinct approaches to organization.

Although systems of classification and categorization are both mechanisms for establishing order through the grouping of related phenomena, fundamental differences between them influence how that order is effected--differences that do make a difference in the information contexts established by each of these systems. While traditional classification is rigorous in that it mandates that an entity either is or is not a member of a particular class, the process of categorization is flexible and creative and draws nonbinding associations between entities--associations that are based not on a set of predetermined principles but on the simple recognition of similarities that exist across a set of entities. Classification divides a universe of entities into an arbitrary system of mutually exclusive and nonoverlapping classes that are arranged within the conceptual context established by a set of established principles. The fact that neither the context nor the composition of these classes varies is the basis for the stability of reference provided by a system of classification. In contrast, categorization divides the world of experience into groups or categories whose members bear some immediate similarity within a given context. That this context may vary--and with it the composition of the category--is the basis for both the flexibility and the power of cognitive categorization (Jacob, 1992).

Figure 1 identifies six systemic properties that serve as a starting point for comparing systems of classification and categorization: (i) process, (ii) boundaries, (iii) membership, (iv) criteria for assignment, (v) typicality, and (vi) structure.

(i) The process of classification involves systematic arrangement of classes of entities based on analysis of the set of individually necessary and jointly sufficient characteristics that defines each class. In contrast, the process of categorization is generally unsystematic but inherently creative in that it need not rely on predetermined definitions but is able to respond to similarity assessments based on immediate context, personal goals, or individual experience.

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Classification and categorization: a difference that makes a difference

Library Trends, Wntr, 2004 by Elin K. Jacob

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