On the peculiarity of simple reaction time

Two experiments are reported in which high-compatibility reaction time (RT) tasks were performed with, and without, a concurrent secondary task. In both experiments, the secondary task interfered to a greater extent with simple RT than with choice RT. In fact, the effect of adding a secondary task was to eliminate the advantage of simple RT over two-alternative-choice RT. Previous studies of this phenomenon employed a task in which subjects raised a finger when it received tactile stimulation, while engaging in continuous reading aloud. The present experiments show that the effect can be obtained using a different stimulus modality (vision) as well as other responses (vocal) and secondary tasks (shadowing, auditory step-tracking). The paradigm provides a means of isolating preparatory processes that are peculiar to the simple RT task.