Seventy-four patients, including 22 schizophrenics, were administered the object-sorting test at the acute stage, and then again 11 months later during the posthospital stage in order to determine whether two types of thought disorders are a permanent characteristic of schizophrenic thinking or only a function of the acute phase of the disorder.
Harrow M, Harkavy K, Bromet E, Tucker GJ. A Longitudinal Study of Schizophrenic Thinking. Arch Gen Psychiatry. 1973;28(2):179-182. doi:10.1001/archpsyc.1973.01750320019003