Using the Relative-Speed-of-Processing to Explain the Shielding Function of Task Rules

In choice reaction tests, applying task rules instead of responding associatively can help participants shield against interference from distractors. However, the mechanism of such shielding functions of task rule remains unclear. In four experiments, we showed that the shielding function can be explained by the Relative-Speed-of-Processing theory. Experiment 1A demonstrated that applying task rules can reduce the relative processing advantage of the distractor by facilitating the target processing speed; therefore, eliminate the interference effect. In Experiment 1B, and 1C, we manipulated the relative processing advantage between targets and distractors by adjusting the temporal sequence of the presence of the targets and distractors: stimuli appeared first would gain more relative processing advantage. The results showed that when the relative processing advantage of a distractor was large enough, applying task rules cannot help participants shield against the interference. In contrast, when the relative processing advantage of the distractor was small, even without applying task rules, participants were not interfered by the distractor. In Experiment 2, we directly manipulated the processing speed of the targets and the distractor, so that participants who responded associatively would facilitate target processing speed, but participants who applied task rule would not. Contrary to previous studies but in line with our prediction, in Experiment 2, only participants who applied task rule had interference effects. Our results suggested that applying the task rule might not help us shield against the interference directly. Instead, applying task rules facilitate the target processing speed which reduces the relative processing advantage of the distractor and eliminates the interference.