Illusory Inhibitory Overlap: Response inhibition and interference control interact only via spatial attention in the flanker stop-signal paradigm

It is debated whether there is overlap between the inhibitory processes required in task requiring inhibition. A key finding supporting inhibitory overlap is that inhibition of actions (response inhibition) is slowed down when conflicting information needs to be suppressed (interference control), indicating a competition between two inhibitory processes. Another account is that there is no overlap, but that interference triggers an attention-related mechanism that interacts with attentional processes in response inhibition. We tested these accounts in two experiments. Our first experiment consisted of a flanker stop-signal paradigm with stop signals presented in the periphery of the stimulus display. Established stop-signal models failed to explain this data, so we modified them to account for an effect of the attentional spotlight on stop-signal processing. Thereby we captured that SSRTs were longer when stop signals appeared later. This alone explained the apparent interaction between response inhibition and interference control. Following, we preregistered a second experiment to test the prediction that the interaction between response inhibition and interference control would be resolved when the stop signal was presented centrally. Indeed, this abolished the interaction. Our work therefore shows that inhibition of response inhibition and interference control do not overlap.