Selection history modulates the effects of dual mechanisms on flanker interference.

The limit of processing capacity and the effectiveness of top-down control are 2 mechanisms that underlie distractor interference in a flanker task. The current study investigates how the interblock selection history shaped by the target number and the predictability of distractor location may modulate the effects of these 2 mechanisms on flanker interference. Experiment 1 showed that the distractor compatibility effect was eliminated when the task array contained 4 or 5 identical targets, which reflected the capacity limit. The target number and distractor location's predictability (Experiment 2) or location predictability and target-distractor proximity (Experiment 3) were manipulated across blocks, while compatibility varied within blocks, with control efficacy underlying the effects of distractor location (predictability and proximity). The interblock selection history was induced by task order, beginning with 2 or 4 targets in Experiment 2 and with a distractor at a fixed or an unpredictable location in Experiment 3. Effects of interblock selection history were found when the intertrial context did not promote an incentive for altering the processing mode. When the incentive for enacting top-down control is high, intertrial contextual factors influence flanker interference. Contextual factors related to the target number and distractor location modulate flanker interference at multiple levels.