Language-dependent performance on the letter fluency task in patients with schizophrenia.
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.
Faculty of Human Development and Culture, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296 Fukushima, Japan. Electronic address: sumiyoshi@educ.fukushima-u.ac.jp.
Chika
C
Sumiyoshi
Department of Psychiatry, Hacettepe University Faculty of Medicine, 06100 Sihhiye, Ankara Turkey.
Aygun
A
Ertugrul
Department of Psychiatry, Hacettepe University Faculty of Medicine, 06100 Sihhiye, Ankara Turkey.
A Elif
AE
Anil Yağcıoğlu
Department of Psychiatry, Vanderbilt University Faculty of Medicine, 2201 West End Ave., Nashville 37235, TN, USA.
Ajanta
A
Roy
Department of Psychiatry, Vanderbilt University Faculty of Medicine, 2201 West End Ave., Nashville 37235, TN, USA.
Karu
K
Jayathilake
British Council, Tokyo, 1-2 Kagurazaka, Shinjuku-ku, 162-0825 Tokyo, Japan.
Alan
A
Milby
Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, 446 East Ontario #7-200, Chicago, 60611, IL USA.
Herbert Y
HY
Meltzer
National Center of Neurology and Psychiatry, 4-1-1 Ogawa-Higashi, Kodaira, 187-8551 Tokyo, Japan.
Tomiki
T
Sumiyoshi
D000328:Adult; D005260:Female; D006801:Humans; D007391:International Cooperation; D007802:Language; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000503:physiopathology*; D012564:Schizophrenic Language; D012565:Schizophrenic Psychology; D014705:Verbal Behavior / Q000502:physiology*; D055815:Young Adult
BACS; CFT; Category fluency; Cross-language diversity; GPC; GT Hypothesis; Grapheme–Phoneme Correspondence; LFT; Letter fluency; PUG; Phonological Unit for a Grapheme; Schizophrenia; VFT; Verbal fluency; Writing system; category fluency task; letter fluency task; the Brief Assessment of Cognition in Schizophrenia; the Hypothesis of Granularity and Transparency; verbal fluency task