Adding Distractors Improves Performance by Boosting Top - Down Control

Adding Distractors Improves Performance by Boosting Top-Down Control Ion Juvina (ijuvina@cmu.edu) & Niels A. Taatgen (taatgen@cmu.edu) Department of Psychology, Carnegie Mellon University 5000 Forbes Avenue, Pittsburgh, PA 15213 Abstract The attentional capture account (Kahneman & Chajczyk, 1983; Mitterer et al., 2003) states that the extra stimulus captures attention on some of the trials, thus causing the Stroop distractor to interfere less often with the Stroop target. - The visual interference account (Brown et al., 1995; MacLeod & Bors, 2002) proposes that recognition of two or more words occurs in parallel. The extra words cause degradation of the early visual percept of the Stroop distractor impairing its recognition, thus making it less able to interfere with the Stroop target. Both accounts postulate bottom-up mechanisms (attentional capture or visual interference) to be responsible for the Stroop dilution effect. The improvement in performance seems to be caused by deteriorating the automatic reading of the word feature of the Stroop stimulus. In other words, the extra stimuli make the distractor less interfering. However, the Stroop task is known to have a top-down component as well (Herd, Banich, & O'Reilly, 2006). None of the studies with which we are familiar was concerned with the impact of the extra stimuli on the top-down component involved in the Stroop task, which is selecting and processing the target. The effect of adding to-be-ignored extra stimuli to a modified Stroop task is investigated. Adding extra stimuli of the same kind as the distractor causes a temporary improvement in performance (Stroop dilution), whereas adding extra stimuli of the same kind as the target causes an improvement in performance that is only detectable when the extra stimuli are removed (post-treatment). An attempt is made to explain these different outcomes in light of the existing theoretical accounts of the Stroop dilution effect. A computational model that accounts for the observed data is proposed. Results suggest that a top-down control mechanism compensates for lateral inhibition effects, particularly when they have a potentially disruptive influence on performance. This boost of control seems to last longer than needed, causing performance improvements in a post-treatment condition. A further implication of these results is that the top-down control function is trainable. Keywords: Stroop dilution; lateral inhibition; top-down control. Background One of the typical functions of our cognitive control system is interference resolution by protecting the execution of task-relevant sequences of actions against interference and distraction. The Stroop task is a landmark task for studying cognitive control and interference resolution (MacLeod, 1991; Miyake, Friedman, Emerson, Witzki, Howerter, Wager, 2000). In this task the participant is presented with a sequence of words written in various ink colors and instructed to name the ink color of each word. There are three conditions: (1) congruent, when the word meaning and the ink color are congruent, for example, the word red is written in red ink; (2) incongruent, when the word meaning and the ink color are incongruent, for example, the word red is written in green ink; and (3) neutral, when the word meaning does not refer to a color name, for example, the word desk written in any color. Typically, it takes more time to name the color of an incongruent word and less time to name the color of a congruent word than to name the color of a neutral word. A common augmentation of the Stroop paradigm is obtained by adding to-be-ignored extra stimuli to the classical Stroop trial. Typically, these extra stimuli are words and they determine an increase in performance on the Stroop task, a phenomenon frequently referred to as Stroop dilution (Brown, Roos-Gilbert, & Carr, 1995; Cho, Lien, & Proctor, 2006; Kahneman & Chajczyk, 1983; MacLeod & Bors, 2002; Mitterer, La Heij, & Van der Heijden, 2003). Two main theoretical accounts have been proposed for the Stroop dilution effect: Experiment In order to study the impact of the extra stimuli on the top- down component of the task, we added a separate condition with extra stimuli of the same kind as the target (extra colors). The hypothesis is that the extra words would cause an increase in performance (Stroop dilution), whereas the extra colors would cause a decrease in performance. The reasoning behind the latter is that the extra colors would disrupt target identification while leaving the distractor with its full interfering potential. We are also interested to know what impact these changes in performance have on a post-treatment condition when the extra stimuli are removed. We hypothesize that, if the changes are solely due to bottom-up mechanisms (attentional capture or visual interference), performance at post-treatment should return to its pre-treatment levels. If post-treatment performance is differentially or similarly affected by the two treatments (extra colors vs. extra words), then other mediating or modulating processes might be involved. Method This experiment is part of a larger project aimed at investigating the cognitive control aspects of multitasking. We are interested in interference control in tasks that