Vehicle Braking is Slower under Dual-Task Conditions: Evidence for “Central” Interference

Participants attempted to perform 2 concurrent tasks superimposed on a car-following task in a driving simulator. In the choice response task, they responded either manually or vocally to whether a visual or auditory stimulus was presented once or twice. In the braking task, they depressed a brake pedal to the onset of the lead car's brake lights. The onset delay between the choice and braking stimuli was varied. This manipulation revealed that the braking reaction was greatly affected by concurrent performance of the choice task, although there were no or very small specific effects on it by the stimulus and response modalities of the choice task. The results demonstrate that even a well-practiced, “simple” task such as vehicle braking is subject to dual-task slowing and appear to be due to central, not peripheral, interference.