Figural Aftereffects and Validity of the Hoffer-Osmond DiagnosticTest

One problem confronting diagnostic tests is the extent to which different diagnostic groups obtain similar scores, or the degree to which patients with the same diagnosis obtain extreme scores on a test. An example of the latter is the HofferOsmond Diagnostic Test or HOD on which approximately 70 percent of schizophrenic patients obtain relatively high scores (above established cutoff points) and 30 percent low scores (Kelm, Hoffer and Osmond, 1981; Kelm and Osmond, 1975). The fact that approximately 30 percent of schizophrenic patients obtain relatively low scores is usually interpreted as a weakness of the Test (Stewart and Mahood, 1963; Task Force, 1973). In one sense this is correct, but there is also the possibility that schizophrenics with high HOD scores may actually have different perceptual experiences than low scorers, and that the HOD is differentiating between perceptual styles in schizophrenic patients who may have different disease states requiring correspondingly appropriate therapies.