Influences of response-activating stimuli and passage of time on the Simon effect.

Two possible explanations for an interaction between the Simon effect and the flanker-congruence effect (Hommel, 1997) were tested: (1) Direct contributions by the locations of the response-activating flankers to the Simon effect, and (2) the passage of time since the target's onset. In three experiments, little evidence for both explanations was observed. The data confirmed an assumed origin of the Simon effect at the stage of response selection. Further, the results are in line with the assumption that context stimuli contribute indirectly to the Simon effect of the target (i.e., by changing the target's relative position), and extend previous findings to show that the assumption holds for clearly response-activating context stimuli, too. Finally, the results suggest that Simon effects follow different time courses depending on whether they are induced by observer-relative or context-relative target positions.