Thought disorder and schizophrenia: isolating and timing a mental event

This study explored the ability of nonparanoid schizophrenic, paranoid schizophrenic, and mixed psychiatric control (manics and schizoaffectives) patients to perform on two types of conceptual, speeded inference (SI) tasks, which differ in type of abstraction process required. The subjects (N = 30) were grouped into high and low levels of thought dysfunction, as measured by the Whitaker Index of Schizophrenic Thinking (WIST). There were no differences among the three clinical groups on the conceptual, SI tasks. Reaction times differed reliably across the two SI tasks. High-WIST subjects were impaired on SI accuracy. Significant impairment in accuracy was demonstrated by high-WIST time and error groups on the more complex SI tasks. Information processing deficit was demonstrated in terms of encoding phase and reaction time in problem-solving of the three diagnostic groups as a function of WIST levels.