The effects of endogenous and exogenous cues on task-set inhibition

Graduation date: 2008Task-set inhibition has been proposed to be an important mechanism for cognitive control in task switching. Its existence is supported largely by the observation of the N-2 repetition cost (e.g., A-B-A is slower than C-B-A). Many studies have reported an N-2 repetition cost, but several have not. Because of the numerous methodological differences between previous studies, no firm conclusions can be drawn regarding the conditions necessary to produce inhibition. To better understand inhibition and its role in task switching, we manipulated factors thought to cause the absence or presence of the N-2 repetition cost in 4 experiments. In Experiments 1-3 where a predictable, repeating task sequence was used, we consistently found an N-2 repetition cost, even under the aforementioned conditions, which have previously been associated with the absence of inhibition. However, when a random task sequence was used in Experiment 4, the N-2 repetition cost was eliminated, at least in the condition where the task set was solely cued by location. The persistence of the N-2 repetition cost in Experiments 1-3 and absence of it in Experiment 4 suggest that spatial information can be useful for improving performance, but only under specific circumstances