ABSTRACT
One of the traditional purposes of assessing social and emotional behavior is to determine an appropriate diagnosis or classification. The term diagnosis historically is linked with the medical model of psychological disorders, whereas the term classification is used more in education and by behaviorally oriented researchers. Both terms imply a common element of categorizing and codifying an observable phenomenon based on an existing taxonomy or scheme. We shall not argue over conceptual or definitional differences between the two terms; both are subsumed under the more generic term classification in this chapter. Both terms are related to the notion of taxonomy, which comes from the Greek verb tassein, meaning “to classify,” and nomos, meaning “law, science.” In the sciences, taxonomic structures are often hierarchical in nature, meaning that they classify phenomena from most important to least important feature. Taxonomies may also include network relationships, which are nonhierarchical. Most people who have completed a middle-school-or high-school-level biology course are familiar with the taxonomic system used to classify living things according to their Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
