The list-wide proportion congruency (LWPC) effect refers to larger congruency effects in blocks with mostly congruent (MC) trials compared to blocks with mostly incongruent (MI) trials. The asymmetrical list shift (ALS) effect describes the observation that congruency effects decrease significantly during MC-to-MI transitions but show little increase during MI-to-MC transitions. This asymmetry has been attributed to rapid recruitment of shielding during MC-to-MI transitions and persistent shielding during MI-to-MC transitions.
This study aimed to replicate the ALS effect using a confound-minimized face-name Stroop task. Participants learned the names of six faces and responded to faces while ignoring the names. Four face-name pairs were conflict-frequency biased, forming MC (80% congruent) and MI (80% incongruent) blocks. Two face-name pairs were unbiased (50% congruency) to assess the transferability of the ALS effect. All participants performed the MC-to-MI and MI-to-MC transition and both transitions included different sets of face-name pairs.
Overall, results revealed both LWPC and ALS effects for biased and unbiased items. Crucially, ALS effects in unbiased items, which were practiced equally in MC and MI blocks, support the assumption of asymmetric control adaptation. Notably, an ALS effect for unbiased items was only observed in participants starting with MC-to-MI transitions, suggesting that the first encounter with a conflict-frequency biased block influences subsequent adaptability.