- The production of association word to stimulus words, which was found to be correlated with conceptual disorganization, as clinically measured by the Brief Psychiatric Rating Scale, was developed as a quantifiable measure of formal thought disorder. Associative word production in patients with affective psychoses (acute episodes of mania or schizoaffective disorder) was found to be higher in a statistically significant manner than in patients with acute episode of paranoid schizophrenia. The production of associative words in the two groups of acutely psychotic patients was significantly higher than in normal subjects, unipolar depressed, or residual schizophrenic patients. These quantitative differences reflected qualitative differences in the pattern of the production of word associations. Indeed, while patients with paranoid schizophrenia showed a sinusoidal-like type of oscillation in associative word production, patients with affective psychoses were characterized by exponential-like phases in associative word production. Associative word production may thus serve as a simple quantitative test for differentiating formal thought disorder in acute psychoses between patients with mania and patients with schizophrenia.