The neutral condition in conflict tasks: the implications of neutral condition RT behavior on modeling

While the relation between congruent and incongruent conditions in conflict tasks has been the primary focus of cognitive control studies, the expectation of neutral condition behavior is oft ignored, or set as directly between the two conditions. However, empirical evidence suggests that average neutral reaction time (RT) contradicts this assumption. The present studies, thus, sought to, first, reinforce the informative nature of the neutral condition and, second, to highlight how it can be useful for modeling. To do this, we first explored how RT in the neutral condition of conflict tasks (Flanker, Stroop, and Simon Tasks) deviated from the predictions of current diffusion models. Many of the deterministic versions of cognitive conflict models predicted a neutral RT that is the average of the congruent and incongruent RT, called the midpoint assumption. This assumption is maintained over the time course, resulting in the parallel assumption. To investigate these assumptions, we first conducted a limited literature search that recorded the average RTs of conflict tasks with neutral conditions. Upon finding evidence of a midpoint assumption violation with smaller RT differences between the congruent and neutral conditions, we tested the prior mentioned conflict tasks with two different, distinct sets of stimuli. The results suggested that a violation of the midpoint assumption is present in different manners depending on the conflict task and the stimuli. Then, a follow up study was performed in order to test the parallel assumption via the Speed-Accuracy Tradeoff paradigm. From the results, clear violations of the parallel assumption were observed in all three conflict tasks. Due to the implications of these violations, the authors then suggested possible elaborations of the Diffusion Model of Conflict to account for these phenomena.