Introduction

This entry treats formal classification procedures, not psychological models of classification behaviour. After specifying the terminology, fundamental concepts of classification are briefly introduced, followed by a short review of the empirical basis of classification. Finally, assignment procedures and the evaluation of a classification system are emphasized.

According to Gordon (1996: 65) classification ‘is concerned with the investigation of a set of objects in order to establish whether or not they fall naturally into groups (or classes, or clusters) of objects with the property that objects in the same group are similar to one another and different from objects in other groups’.

Differential and clinical psychology frequently solve problems of classification in several different areas: persons are characterized by typologies, one finds classifications of tasks and situations, intervention ...