ABSTRACT
Psychology has been called the science of human behavior (e.g., Hilgard, 1987;
O’Donohue & Krasner, 1995; Plaud & Eifert, 1998). As scientists-whether basic or
applied-psychologists engage in one of the most fundamental steps common to any
scientific endeavor, that of classifying the phenomena of interest. Within psychology,
particularly the more applied branches, this activity of classification is more commonly
known as diagnosis. Scientists typically take one of two approaches to the issue of
classification: inductive-“bottom-up”—or deductive-“top down,” (see Cone, 1986,
1988). These two approaches are most closely related, within psychology, to the person-
centered and behavior-focused idiographic approach, and the group-oriented (or
norm-referenced) and trait-focused nomothetic approach (see Cone, 1986,1988), although
these distinctions rarely are stated explicitly and typically are highly overlapping. A key
difference in these two approaches to the subject matter is that, in the inductive approach,
one accumulates multiple observations about typical and atypical behavior and orders
them along dimensions of similarity and dissimilarity. The taxonomy that this creates
becomes the basis for further observations and eventually leads to the development of
theory-in this case, theories of behavior and psychopathology In the deductive
approach, one begins with theory (although this clearly must be based on at least an
informal observation of behavior) and seeks to gather data that confirm or disconfirm the
theory.
