The relative attractiveness of distractors and targets affects the coming and going of item-specific control: evidence from flanker tasks.

The item-specific proportion congruence (ISPC) effect refers to the attenuation of interference for mostly incongruent relative to mostly congruent items. In the present study, qualitatively different ISPC effects were observed in letter- and arrow-based flanker tasks despite their common use of the original two-item set design. Consistent with the predictions of the dual item-specific mechanisms account, contingency-driven ISPC effects were observed when stimuli were used that attracted attention to the irrelevant dimension (Experiments 1, 3, and 6), whereas control-driven ISPC effects were observed when attention was attracted to the relevant dimension (Experiments 2, 4, and 5). The evidence for control-driven ISPC effects in the two-item set design (1) challenges the contingency account, which claims that ISPC effects are solely contingency-driven, and (2) supports an expanded definition of cognitive control that includes fast and flexible adjustments that minimize attention to distractors upon encountering stimuli that have previously been associated with a history of conflict.