The authors used the Thought Disorder Index to measure thought disorder in 23 patients with unilateral right hemisphere cortical damage, 20 patients with bipolar mania, and 25 patients with schizophrenia. There were no differences in the total amount of thought disorder in these groups, but each showed a unique pattern of thought disorder. Patients with right hemisphere damage displayed fragmented thinking, manic patients displayed playful thinking, and schizophrenic patients displayed idiosyncratic thinking. These findings support the view that thought disorder is manifested in different forms that are relatively specific to psychiatric or neurological condition.