Effect of additional tasks on the reaction time of braking responses in simulated car driving: beyond the PRP effect

Abstract

Abstract It well established that the presentation of one task increases the reaction time on a subsequent task, if the stimulus onset asynchrony (SOA) between tasks is less than about 400 ms. This psychological refractory period (PRP) effect has been observed both in classical laboratory paradigms and in simulated car driving. Here we report about an effect that persists substantially longer than the PRP effect. In a driving simulator, 120 healthy older participants followed a lead car that mostly drove at a constant speed, and they had to brake when the lead car braked. Concurrently, they engaged in several additional tasks. SOA between the braking task and the last preceding additional task was about 11.5 s. In a control condition, the braking task was administered without additional tasks. We found that the reaction time of braking responses averaged 0.77 s without additional tasks, but averaged 1.45 s with additional tasks. This increase was less pronounced at smaller inter-vehicle distances, and was not compensated by faster foot movements from the gas pedal to the brake pedal. We conclude that detrimental effects of additional tasks on subsequent braking responses can be much more persistent than the PRP effect, possibly because of the need to maintain multiple task sets. We further conclude that the detrimental effects can be ameliorated at small inter-vehicle distances, possibly by mobilizing extra cognitive resources when response urgency is high. As a practical implication of our study, distracting stimuli can have persisting detrimental effects on traffic safety.