This study examines the irrelevant speech effect (ISE) and the effects of individual differences (introversion/extroversion and field dependence/independence: FDI) on the Wisconsin Card Sorting Test (WCST) and the Stroop Test. In Experiment I, irrelevant speech and silence groups performed the WCST. Unlike the ISE, FDI affected four WCST indexes (CA, TE, PE [Milner], and PE [Nelson]) but did not affect the WCST DMS index, which shows the difficulty of maintaining concepts. However, the ISE was observed with the DMS. In Experiment 2, WCST data were applied under a noise condition. In Experiment 3, the Stroop Test revealed that individual differences affect the amount of conflict, unlike the ISE. In general, the ISE is understood to relate to the phonological loop of the working memory, with individual differences related to the central executive system. We believe that the WCST involves the central executive system and phonological loop, while the Stroop Test primarily involves the central executive system.

Key words: Field dependence/independence, introversion/extroversion, irrelevant speech effect, Stroop Test, WCST.