Effector system-specific sequential modulations of congruency effects.

Congruency effects in conflict tasks are reliably reduced after experiencing conflict, that is, following incongruent trials. Such sequential modulations (sometimes referred to as the Gratton effect) indicate the operation of conflict adaptation mechanisms. The influential conflict monitoring hypothesis suggested that after conflict the processing of relevant stimulus dimensions is increased. Alternatively, it was suggested that the influence of automatic response activation is suppressed following conflict. In two experiments, participants worked on the same cognitive task (Experiment 1: Eriksen flanker; Experiment 2: Simon) with the same kind of stimulation. A cue indicated whether they should respond with the hands or the feet. When the effector system repeated from the previous trial, a sequential modulation was reliably observed. When the effector system switched, however, the sequential modulation collapsed. These results are taken to argue for the suppression of effector system-specific response activations as a consequence of experiencing conflict. Alternative interpretations in terms of task-set and/or context switches are discussed.