What is the nature of increased Stroop interference in schizophrenia?

In comparison to controls, patients with schizophrenia classically display (1) an overall slowing in response times (RTs) and (2) a disproportionate s lowing in RTs in the conflict condition of the Stroop color/word interferen ce task. These two effects appear repeatedly in the card version of the Str oop task but were not replicated in a number of studies using a computer it em-by-item version of the task. The present study was aimed at understandin g the exact nature of the increased interference classically found in the p erformance of patients with schizophrenia in the card version of the Stroop task. We used a computer trial-by-trial version in which we investigated t he effects of two major methodological differences between the two versions : (1) blocked (card version) versus mixed (computer version) presentation o f the neutral, congruent and conflict conditions and (2) presence (card ver sion) versus absence (computer version) of distracters in the spatial surro unding of the target. We found an overall slowing in performance and a disp roportionate slowing in the conflict condition for patients with schizophre nia but only when the target was surrounded by distracters (in Experiments 2 and 3). The data are discussed in terms of a deficit in selective attenti on and inhibitory processes in schizophrenia. (C) 1999 Published by Elsevie r Science B.V. All rights reserved.