This study adopted the perspective of CEST (Epstein, 1994), and examined whether the Japanese version of REI (Naito, Sakamoto, and Suzuki, 2000), which measures rational and experiential thinking styles, was related to performance in a ratio-bias paradigm (Study 1), and the Linda problem (Study 2). Study 1 revealed that rational thinking style was inversely related to nonoptimal responses in the ratio-bias paradigm, while experiential thinking style was unrelated to it. These results were consistent with the results of Pacini and Epstein (1999). Study 1 also suggested the possibility that the ratio-bias paradigm was not adequate for identifying the function of the experiential system. Study 2 revealed that rational thinking style was inversely related to nonoptimal response in the Linda problem, while experiential thinking style was positively related. These results demonstated the utility of the Japanese version of REI for examining individual differences on judgment, as well as the necessity of using a task which can clearly identify the functions of both systems.
