A Quantification of Diagnostic Differentiae

Abstract

The more recent and better designed studies of the reliability of psychiatric diagnosis (Schmidt and Fonda, 1956; Norris, 1959; Kreitman, 1961; Kreitman et al. 1961) suggest that the earlier pessimism may not be entirely justified. At the present time it seems safest to conclude that there are some states that some psychiatrists can diagnose reasonably reliably under some conditions. Nevertheless, even if psychiatrists could be shown to be highly reliable under optimal conditions, their diagnoses could only serve as the criterion by which to develop some more objective, public and quantitative means of classification, since the optimal conditions cannot readily be met in routine practice. It is desirable that any such quantitative scale should be reasonably compatible with existing psychiatric classification. As Eysenck (1960) has argued, “the degree of correspondence observed is of some interest in making possible the translation of experimental findings from one field to the other…. Even if there were no correspondence at all with psychiatric diagnostic classifications, this would not in any way invalidate the empirical findings”.