The effects of verbalisation on cognitive performance in schizophrenia: a pilot study using tasks from the Delis Kaplan Executive Function System.

Cognitive impairment is common in schizophrenia, and has adverse effects on functional outcome. Cognitive remediation strategies in which people with schizophrenia speak aloud (verbalise) during task performance have demonstrated some success in improving performance on the Wisconsin Card Sorting Test. This study extends previous research by assessing whether verbalisation also improves performance on tasks selected from the Delis-Kaplan Executive Function System (D-KEFS). Twenty two subjects with schizophrenia participated in the study. We used a within subjects design to compare performance on the D-KEFS Tower Test and Trail Making Test when participants (a) produced concurrent verbalisation, or (b) remained silent. Results demonstrated selective benefits of verbalisation on a neuropsychological task requiring multiple executive functions (number-letter switching task), while performance on tasks requiring simpler single-component cognitive functions (visual scanning and motor speed tasks) was adversely affected. The effects of verbalisation on the cognitive task performance of patients with schizophrenia differ depending on the nature of the task. Benefits are seen in tests of executive skills but performance worsens in single component cognitive tasks. When developing cognitive remediation strategies for people with schizophrenia, consideration should be given to the nature and cognitive demands of each task before recommending verbalisation strategies.