A further attempt to cross-validate the grid test of schizophrenic thought disorder.

A retrospective investigation to assess the validity of the Grid Test of Schizophrenic Thought Disorder (Bannister & Fransella, 1966, 1967) is reported. Analysis of the data revealed that, while there is some evidence to support the validity of the test, it failed to discriminate between clinically assessed thought-disordered and non-thought-disordered patients at an acceptable level of significance, and that the rate of misclassification was too high to justify the use of the test in the assessment of an individual case. The results are compared with the findings of other published studies, and weaknesses in methodology, due to the retrospective nature of the study, are also discussed.