The effect of task location and task type on backward inhibition.

Alternating tasks in a sequence of task switches results in impaired performance, relative to switches across three different tasks, an effect known as backward inhibition. Despite the robustness of this effect across task and response variations, backward inhibition is not observed when tasks are uniquely located at different points in space (Arbuthnott, 2005). Three hypotheses about the source of this anomaly were tested. Experiment 1 indicated that perceptually distinct task features other than location did not eliminate backward inhibition. Experiment 2 indicated that when switches across task and location were manipulated independently (i.e., all tasks appeared at all locations), backward inhibition was observed for task switches even when consecutive trials appeared at different spatial locations, ruling out eye movement as the source of the difference. The third experiment indicated that when component tasks involved judgments of spatial location, backward inhibition was observed across unique task-location switches. These results indicate that sequential inhibition is a very flexible mechanism that is sensitive to the amount of interference from previous tasks.