Controlling Decision Conflict

In tasks such as the Simon, Stroop, and Flanker, different attributes of a choice stimulus can be associated with conflicting responses. These tasks have been widely used to afford insights about cognitive control by comparing performance when the attributes are congruent vs. incongruent. It is usually assumed that standard evidence-accumulation models (EAMs), which were originally developed to explain simple choices about non-conflict stimuli, cannot accommodate the fine-grained effects of congruency on the speed and accuracy of responses in conflict tasks. We investigated this assumption by fitting data from over 500 subjects performing each of these three conflict tasks using five types of standard EAMs drawn from two classes, race and dual-diffusion models. For each type, we fit a range of variants that explain conflict effects using one or more parameter differences. We found that the two dual-diffusion models could not accommodate the fine-grained effects of congruency, but the three race models could. All the race models explain the congruency effects in the same way, with mechanisms that affect the amount of evidence required to decide, and the variability of that evidence. We discuss how this combination of mechanisms suggests a novel “conflict-cancelation” theory of cognitive control.