Verbal fluency tasks are frequently used in clinical
neuropsychology. Clustering (the production of words within
semantic subcategories) and switching (the ability to shift
between clusters) have been described as 2 components underlying
fluency performance. We compared the use of clustering
and switching in schizophrenic patients and healthy subjects.
Seventy-eight schizophrenic subjects (DSM–IV criteria)
and 64 control participants matched for age and educational
level were recruited. Negative, disorganized, and productive
clinical dimensions were evaluated using the SANS and SAPS
scales. The number of words generated per semantic–phonemic
cluster and the number of switches were evaluated during
2 verbal fluency tasks (phonemic and semantic). In the
healthy controls switching and clustering were closely
related to the total number of words generated in the verbal
fluency tests. The role of the 2 components was partly
dependent on the specific task. Switching was prevalent
in formal fluency, while both switching and clustering
contributed to semantic fluency. In comparison to the healthy
controls, the overall group of schizophrenic patients showed
a significant impairment of switching in the formal fluency
task and of both switching and clustering in the semantic
fluency task, and both the negative and disorganized dimensions
correlated with verbal fluency performance, the number
of switches during the phonemic fluency task, and the clustering
during semantic fluency task. (JINS, 1998, 4,
539–546.)