Current theories posit multiple levels of cognitive control for resolving conflict, including list-level control: the global or proactive biasing of attention across a list of trials. However, to date, evidence for pure list-level control has largely been confined to the Stroop task. Our goals were twofold: (a) test the generality of theoretical accounts by seeking evidence for list-level control in the letter flanker task, using an established method involving diagnostic items, and investigating the conditions under which list-level control may and may not be observed and (b) develop and test a potential solution to the challenge of isolating list-level control in tasks with a relatively limited set of stimuli and responses such as arrow flanker. Our key findings were that list-level control was observed for the first time in a letter flanker task on diagnostic items (Experiment 1), and it was not observed when the design was altered to encourage learning and use of simple stimulus-response associations (Experiment 2). These findings support the generalisability of current theoretical accounts positing dual-mechanisms or multiple levels of control, and the associations as antagonists to control account positing that list-level control may be a last resort, to conflict tasks besides Stroop. List-level control was also observed in the arrow flanker task using a modified design (Experiment 3), which could be extended to other conflict tasks with limited sets of stimuli (four or fewer), although this solution is not entirely free of confounds.
Keywords: Cognitive control; flanker task; proactive control; proportion congruency effects.