Conflict monitoring and feature overlap: two sources of sequential modulations.

Recent findings demonstrating that the Simon effect diminishes when the preceding trial is a noncorresponding trial led researchers to develop two alternative accounts. The conflict monitoring account argues that the automatic activation from stimulus location information is under the regulation of a control mechanism, which adjusts the level of activation depending on conflict in the preceding trial. In contrast, the feature integration account holds that sequential modulations of the Simon effect can be attributed to the integration of stimulus and response features into event files. Previous research demonstrated a potential contribution to sequential modulations from both mechanisms. We use a four-choice task to extend these findings and to investigate the exact nature of the feature overlap effects. Both conflict monitoring and feature overlap effects were found to contribute to sequential modulations. However, the feature overlap effects did not conform to predictions of the feature integration account. We argue that the feature overlap effects are accounted for better by strategic shortcuts in response selection.