Secondary verbal responses during driving may not be a safer alternative to manual responses irrespective of age

It has been shown that older vs. young people experience increased motoric interference between sensorimotor tracking tasks and secondary manual responses during driving-like dual tasks [1] and simulated driving [2]. The present study investigated whether a verbal response mode represents a better alternative for secondary responses in order to decrease task interference during simulated driving. Young (N=20, 25-25 years, 10 women) and older participants (N=20, 60-69 years, 10 woman) performed a dual task in a driving simulator. They had to navigate a simulated car on the road. In a single task control condition they had either to drive or to perform a visual attention task with manual or verbal responses whereat the visual stimuli were displayed on the front windshield. In the dual task condition the visual attention task had to be performed while driving. Participants had to respond both with verbal and manual responses, respectively. Generally, older vs. young participants showed significantly slower and more erroneous responses to the secondary task stimuli. Independent of age, responses to secondary stimuli were slower in the dual task compared to the single task condition. Both groups omitted more responses in the verbal than in the manual condition. Importantly, the overall tracking performance in the dual task with verbal responses was significantly impaired. Taken together, independent of age, verbal responses do not seem to be a better alternative compared to secondary manual responses during simulated driving.