Response conflict and proactive control have independent effects on spatial Stroop performance

The Stroop task has often been used to understand the dynamics of interference resolution in cognitive control. In this study we are using a spatial version of the Stroop task. In this variant, the stimuli consist of arrows that are characterised both by the position in which they appear (relative to a central fixation cross) and the direction towards which they point. The task consists in indicating the direction (relevant dimension) of the arrow, while ignoring its position (irrelevant dimension). The first manipulation introduced in this study is the one targeting the proportion of congruency (PC), which consists in changing the probability with which congruent trials appear within a given block. It has been observed that blocks that contain a high percentage of incongruent trials (i.e., with a low list-wide PC, LWPC) are able to induce a form of top-down, anticipatory attentional bias that has been referred to as proactive control in the Dual Mechanism of Control (DMC) model. On the contrary, when the LWPC is higher, there will be lower engagement of proactive control since its maintenance would be costly and not useful in these blocks. The other manipulation instead is originally trying to manipulate the response conflict, changing the frequencies of each of the four eligible responses. It is assumed that a different type of control is employed to solve the interference that arises at the level of the response for incongruent trials. This study aims at tackling these issues and shed light on the interplay between the (proactive) control processes to solve the interference at the stimulus/task and response levels, while taking into account different theoretical backgrounds with contrasting hypotheses regarding the independence or interaction between them. The results obtained in this study point towards the direction of a non-dependence between the effects of response conflict and proactive control on the response times.