Temporary Decline of Thinking Ability due to Foreign Language Use

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15300085
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Cognitive science
• Research Institution: The University of Tokyo
• Principal Investigator: TAKANO Yohtaro The University of Tokyo, Graduate School of Humanities and Sociology, Professor, 大学院・人文社会系研究科, 教授 (20197122)
• Project Period (FY): 2003 – 2004
• Keywords: foreign language side effect / thinking / language / foreign language effect / attention / foreign language / intelligence

Research Abstract

The present study investigated in two experiments whether the foreign language effect would occur in everyday settings as well.
The foreign language effect refers to a phenomenon that thinking ability (i.e., ability to perform non-verbal information processing) is reduced temporarily while one is using a foreign language in which she is not so skilled as in her own mother language. This phenomenon was first verified empirically and a theoretical explanation as to the process of its occurrence was first provided by Takano and Neda (1993, 1995).
The present study was conducted as a part of a series of studies aimed at investigating whether this foreign language side effect occurs in everyday settings where a foreign language is used. In such settings, materials of thinking are often given verbally, and thus thinking is possibly accompanied by not only non-verbal information processing but also verbal information processing. In other words, thinking may be accompanied by internal language. In most cases, this internal language will be mother language, which is easier to process. When thinking is accompanied by internal mother language, however, the foreign language side effect may not occur. In general, the more similar two concurrent lines of information processing, the stronger interference between them. When thinking is accompanied by internal mother language, the interference is stronger and thus performance is lower when mother language is used as external language than when foreign language is used as external language. This lower performance may well cancel out the foreign language side effect.
To examine this possibility, Experiment 1 required participants to judge validity of syllogistic statements, and Experiment 2 required participants to answer problems which were designed to assess verbal intelligence. Participants (undergraduate and graduate students) performed one of these thinking tasks and a verbal task at the same time.
In either experiment, the performance in the thinking task was lower when the concurrent verbal task was given in the foreign language (i.e., English) than when it was given in the mother language (i.e., Japanese). These results indicate that the foreign language side effect could occur in everyday settings as well, in which thinking is often accompanied by internal language.