Methodological considerations regarding the association of Stroop and verbal fluency performance with the symptoms of schizophrenia

Previous research on schizophrenia has reported conflicting findings regarding the association between Stroop performance and the disorganization syndrome, as well as performance on verbal fluency tests and the psychomotor poverty syndrome. In the present work, we consider whether these inconsistencies may be increased due to variations in test format and failures to report the appropriate test parameters. In 36 schizophrenic inpatients, we administered list and single-trial versions of the Stroop test, and report the correlation with the disorganization syndrome for both errors and speed. For verbal fluency, we separated the total score into measures of switching and clustering, and observed the relationship with psychomotor poverty. For both versions of the Stroop test, accuracy, but not speed, was correlated with disorganization. For verbal fluency, decreased cluster production relative to total words generated was associated with psychomotor poverty, but the number of switches between clusters was not. It is suggested that assessing and reporting a full range of test parameters can reduce between-study inconsistencies. Cognitive interpretations for the present set of results are discussed.