Increased Stroop facilitation effects in schizophrenia are not due to increased automatic spreading activation

Studies using the single trial Stroop task consistently reveal increased re action time (RT) facilitation effects among schizophrenia patients. One pos sible mechanism underlying this effect is increased automatic spreading act ivation in semantic networks. The current study was designed to test this h ypothesis. We administered the Stroop task and two semantic priming tasks t o the same subjects. Patients showed greater Stroop RT facilitation than co ntrols, no evidence of increased semantic priming at short stimulus onset a synchronies (SOAs), and reduced semantic priming at long SOAs. In addition, abnormal Stroop performance was related to the severity of Disorganization symptoms. These results are inconsistent with the spreading activation hyp othesis. Alternative hypotheses regarding the source of Stroop task perform ance deficits in schizophrenia are discussed. (C) 1999 Elsevier Science B.V . All rights reserved.