Faculty of Human Development and Culture, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296 Fukushima, Japan.
Department of Psychiatry, Hacettepe University Faculty of Medicine, 06100 Sihhiye, Ankara Turkey.
Schizophr Res. 2014 Feb;152(2-3):421-9. doi: 10.1016/j.schres.2013.12.009. Epub 2014 Jan 17.
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.
两种类型的言语流畅性任务（字母流畅性任务；LFT，类别流畅性任务；CFT）已广泛用于评估包括精神分裂症在内的精神疾病患者的认知功能。LFT 的任务需求被认为因语言而异，因为认知过程在很大程度上依赖于语音和书写系统。具体来说，字母（s）的音位单位和它们之间的联想方式被认为与表现相关。在当前的研究中，使用日语、土耳其语和英语精神分裂症患者进行了三项分析，以检验这一问题。根据单词搜索的灵活性，假设字母流畅性障碍的严重程度将按日语、土耳其语和英语患者的顺序排列。首先，比较了日语（N=40）、土耳其语（N=30）和美国（N=31）患者的 LFT 和 CFT 表现（分析 1）。仅在美国和其他两组之间发现 LFT 存在显著差异。其次，通过对比日语（N=20，土耳其语：N=30）与正常对照组的脱联程度，比较了日语和土耳其语患者的言语流畅性表现（分析 2）。在日语患者中，与 CFT 相比，LFT 的表现受损更为严重，而在土耳其患者中则发现了相反的趋势，这表明日语患者的字母流畅性表现更为严重。最后，进行了分析 3 以检验日语、土耳其语和英语精神分裂症患者之间字母流畅性障碍的相对顺序。根据之前的元分析综述，估计了英语使用者精神分裂症患者的字母流畅性障碍分离度。日语样本的字母流畅性缺陷的效应量（ES）最大，而其他两组的 ES 相似。这三项分析的结果部分支持了精神分裂症患者字母流畅性障碍严重程度的假设。认为字母流畅性障碍的语言依赖性可以用基于语音和书写系统独特属性的理论模型来解释。这里提出的考虑因素将为优化跨语言认知任务的可移植性提供有用的信息。
