The effect of cognitive distraction on perception-response time to unexpected abrupt and gradually onset roadway hazards.

OBJECTIVE A driving simulator study was conducted to investigate the effect of cognitive distraction on different stages of perception-response time (saccade latency, processing time, and movement time) to unexpected roadway hazards, both when the hazard onset is abrupt and when it is gradual. BACKGROUND Prior studies, which typically focus on overall response times, have demonstrated that distraction, including cognitive distraction, leads to an increase in response times. Studies have also shown that response times differ depending on the type and location of the hazard. However, there is limited research into the effect of cognitive distraction for gradually developing hazards (e.g., a left-turn across path vehicle), as existing research primarily focuses on abrupt hazard onsets (e.g., lead vehicle braking). METHOD Twenty-four participants were presented with three different emergency roadway hazards, including one abrupt onset hazard (a pedestrian stepping onto the roadway from in front of a parked vehicle) and two gradually developing hazards (an oncoming vehicle turning left across the driver's path and a vehicle accelerating perpendicularly into the driver's path from the right). Half of the participants completed a delayed digit recall task (cognitive distraction condition), the other half did not (control condition). RESULTS The left-turn across path hazard was particularly characterized by the long processing period (initiation of the saccade towards the hazard to initial motor response), whereas the pedestrian hazard was more notable for the shortest saccadic latency (hazard onset to the start of the saccade towards the hazard). Cognitive distraction led to a significant increase in brake reaction time for the right-incursion vehicle hazard, in processing time for the left-turn across path hazard, and a marginally significant increase in saccadic latency for the pedestrian and right-incursion vehicle hazards. CONCLUSION Hazard ambiguity due to gradual onset, such as with the left-turn across path hazard, appears to increase the processing duration before a response is executed, especially when distracted. Abrupt hazard onset appears to induce shorter saccadic latencies than gradual onsets likely due to a stronger attentional capture property. However, cognitive distraction may increase saccadic latencies for these types of hazards.