Clustering and switching strategies in verbal fluency tasks: Comparison between schizophrenics and healthy adults

Verbal fluency tasks are frequently used in clinical neuropsychology. Clust ering (the production of words within semantic subcategories) and switching (the ability to shift between clusters) have been described as 2 component s underlying fluency performance. We compared the use of clustering and swi tching in schizophrenic patients and healthy subjects. Seventy-eight schizo phrenic subjects (DSM-IV criteria) and 64 control participants matched for age and educational level were recruited. Negative, disorganized, and produ ctive clinical dimensions were evaluated using the SANS and SAPS scales. Th e number of words generated per semantic-phonemic cluster and the number of switches were evaluated during 2 verbal fluency tasks (phonemic and semant ic). In the healthy controls switching and clustering were closely related to the total number of words generated in the verbal fluency tests. The rol e of the 2 components was partly dependent an the specific task. Switching was prevalent in formal fluency, while both switching and clustering contri buted to semantic fluency. In comparison to the healthy controls, the overa ll group of schizophrenic patients showed a significant impairment of switc hing in the formal fluency task and of both switching and clustering in the semantic fluency task, and both the negative and disorganized dimensions c orrelated with verbal fluency performance, the number of switches during th e phonemic fluency task, and the clustering during semantic fluency task.