Reduced congruency effects only for repeated spatial irrelevant information.

Repeating irrelevant information on successive trials tends to temporarily reduce congruency effects. Despite general explanations extending to all stimulus types, this congruency modulation is mainly observed when using spatial irrelevant information. For non-spatial irrelevant information, the modulation is inconsistent. The present study tested the validity of these general hypotheses by studying the congruency modulation with spatial and non-spatial irrelevant information in a flanker task, thereby minimizing task differences. The results show that the modulation only occurs with spatial information (Experiment 1 & 4) and that it is not related to automatic response activation often attributed to arrow stimuli (Experiment 2 & 3). Therefore, theories based on mechanisms that work on all types of stimulus features fail. These results require explanations in terms of sustained-suppression to be limited to either spatial information, to large conflict situations, or to response conflicts. Interestingly, the present data are also in line with the original spatial attention-shift hypothesis.