Theories of cognitive control argue that response conflict in speeded performance tasks leads to adaptive changes, such that irrelevant information is better ignored on subsequent trials. This study tested whether trial-by-trial changes are driven primarily by conflict on incongruent trials or instead by congruent trials, in which irrelevant and relevant stimulus dimensions match. In a Stroop task including congruent, incongruent, and neutral trials, interference was greater following congruent compared to incongruent and neutral trials, which did not differ. During the intertrial interval, EEG alpha power, an inverse measure of cerebral activation, was significantly lower following congruent than neutral trials, whereas incongruent and neutral trials did not differ. These results imply that trial-by-trial changes in performance may not be driven solely by conflict, but rather by changes in attention triggered by congruent information.

We presented participants with a temporal order judgment (TOJ) task with vibratory stimuli presented to the ends of held tools. We manipulated whether the hands and tools were uncrossed or crossed, predicting that participants would respond more accurately if the responding body part and tool tip were in the same hemispace (see Yamamoto and Kitazawa, 2001). Participants were split into two groups (24 subjects in each group). One group responded manually with the stimulated tools, the other group responded with foot pedals. Contrasting previous findings, we found no significant effect of manipulating tool position when the hands were uncrossed, regardless of response type. Effects of response type were also observed, as participants were significantly more accurate when responding with the stimulated tools compared to responding with foot pedals. Interactions were also found between response type and sex. Compared to males, females made a substantially greater number of confusion errors when responding with feet, but not when responding with tools. Additionally, compared to males, females made substantially more confusion errors with the arms crossed, reflecting previously reported results in tactile TOJ on the hands (Cadieux et al., 2010). These results suggest potential differences in spatial mapping and tactile processing in males and females.