Validity and clinical utility of the grid test of schizophrenic thought disorder

It is suggested that a clearer distinction should be made between the statistical validity and the clinical utility of the Grid Test of schizophrenic thought disorder. The results of three published studies are examined, and in each case the Grid Test is found to have appreciable statistical validity in terms of correlations between grid predictions and clinical judgements of thought disorder. Two criteria are proposed for assessing the usefulness of the Grid Test as a diagnostic instrument, and from an examination of the results of three published studies it is concluded that, despite its statistical validity, the test, at least in its present form, has no appreciable clinical utility.