Abstract
Two types of verbal fluency tasks (letter fluency task; LFT, category fluency task; CFT) have been widely used to assess cognitive function in people with psychiatric diseases including schizophrenia. The task demand of the LFT is considered to vary across languages, as the cognitive process largely relies on sound and writing systems. Specifically, a sound unit for a letter (s) and a manner of association between them are assumed to be related with the performance. In the current study, three analyses have been conducted to examine this issue, using Japanese, Turkish, and English-speaking patients with schizophrenia. It was hypothesized that severity of letter fluency impairment would be in the order of Japanese, Turkish, and English speaking patients according to the inflexibility of a word search. First, performance on the LFT and the CFT was compared among Japanese (N= 40), Turkish (N= 30), and the US (N= 31) patients (Analysis 1). A significant difference was found between the US and other two groups only in the LFT. Second, verbal fluency performance was compared between Japanese and Turkish patients by contrasting the degree of disassociations from normal controls (Japanese: N= 20, Turkish: N= 30) (Analysis 2). In Japanese patients, performance on the LFT was more severely impaired compared to that on the CFT while the opposite trend was found in the Turkish counterpart, suggesting that letter fluency performance was more degraded in Japanese patients. Finally, Analysis 3 was conducted to examine the relative order of letter fluency impairment among Japanese, Turkish and English-speaking patients. Disassociation in English users with schizophrenia was estimated based on previous meta-analytic reviews. The effect size (ES) for the letter fluency deficit was the largest in the Japanese sample, while the other two groups share similar ESs. The results from the three analyses partially supported the hypothesis for the severity of the letter fluency impairment in patients with schizophrenia. The language-dependency of letter fluency impairment was thought to be explained by the theoretical model built on unique properties of sound and writing systems. The considerations presented here would provide useful information for optimizing the portability of cognitive tasks across languages.
Original language | English (US) |
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Pages (from-to) | 421-429 |
Number of pages | 9 |
Journal | Schizophrenia Research |
Volume | 152 |
Issue number | 2-3 |
DOIs | |
State | Published - Feb 2014 |
Funding
This research was supported by Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (C) (No. 22530691) to CS as well as Labour Sciences Research Grants for Comprehensive Research on Disability, Health, and Welfare (H23-Seishin-Ippan-002; H24-Seishin-Ippan-002) and SENSHIN Medical Research Foundation to TS. Those institutions had no further role in the study design, in the collection, analysis, and interpretation of data, in writing the report, or in decision to submit the paper for publication.
Keywords
- Category fluency
- Cross-language diversity
- Letter fluency
- Schizophrenia
- Verbal fluency
- Writing system
ASJC Scopus subject areas
- Psychiatry and Mental health
- Biological Psychiatry