Abstract

The conflict effect is typically smaller following incongruent than congruent trials, and this trial-by-trial modulation has been interpreted as evidence for increased top-down control for efficient selection of task-relevant information. An alternative explanation suggests that this modulation is due to bottom-up feature integration, the notion that stimulus and response features from one trial are automatically bound in an event file. Therefore, complete repetition or alternation of stimulus and response features across trials results in better performance than partial repetition of features, since the latter requires unbinding of the event file from the previous trial. In the present study, using the Simon task, we examined how working memory capacity (WMC) is related to the top-down and bottom-up components of the modulation of the conflict effect. We found that: 1) WMC was negatively correlated with the trial-by-trial Simon effect on partial repetition trials, the portion that reflects top-down control processing. 2) WMC was not associated with the Simon effect of complete repetitions and alternations, the portion that reflects bottom-up processing. 3) Medium and high WMC individuals may be using a different strategy than low WMC individuals. In combination, our findings lend insight into factors that may relate to the trial-by-trial modulation of the Simon effect. Implications for these findings are discussed.