Employing the Diffusion Model for Conflict Tasks (DMC) to clarify the influence of target eccentricity on information processing in the visual Simon task
Mon—HZ_10—Talks2—1302
Presented by: Ruben Ellinghaus
Conflict tasks subsume a variety of experimental paradigms which demonstrate that a task-irrelevant information source can interfere with response selection. For example, the visual Simon effect refers to prolonged and more erroneous responses when the task-irrelevant stimulus location is incongruent with the response side. To account for the processes underlying such performance decrements, the Diffusion Model for Conflict Tasks (DMC) assumes a superimposed diffusion-decision process that combines activations from time-independent target-based processes and time-varying distractor-based processes. The present study demonstrates the power of applying DMC analyses to better understand the temporal dynamics of conflict processing in the visual Simon task. Specifically, we aimed at clarifying how target eccentricity - one of the task’s core parameters – affects processing. Regardless of whether eccentricity was manipulated on a trial-by-trial basis (Experiment 1) or blockwise (Experiment 2), DMC analyses revealed that the increased mean Simon effects with far targets are due to decreases in the rate of target-based evidence accumulation. Furthermore, in Experiment 1, distractor-based activation also increased with far targets, suggesting a relative coding of target locations, such that intermixed locations serve as a reciprocal spatial reference. Thus, target eccentricity can directly impact the strength of both target and distractor processes, rather than solely influencing their temporal overlap – an explanation previously suggested. Overall, the present study shows that DMC analyses help to dissociate the effects of experimental manipulations on different aspects of conflict processing (i.e., strength and timing of target and distractor processing).
Keywords: Simon, SRC, Mental Chronometry, Diffusion Model, Mathematical Psychology, Conflict Tasks