Easy listening or driving distraction? The relationship between audiobook complexity level and driving performance on simple routes

Drivers engage in a variety of secondary activities while driving. Research suggests that many secondary tasks interfere with driving, making performance worse as compared to single-task driving, but a recent study suggests that in simple environments (low scenery and traffic) listening to an audiobook may actually benefit driving performance. Nonetheless, these effects may vary based on both the textual complexity of the audiobook and the working memory capacity of the driver. In this study, we used a driving simulator to compare single-task driving with that when the driver was listening to an audiobook (dual-task). We manipulated the complexity of the audiobook as measured by Lexile scores (a standard index of text difficulty). Licensed drivers did two 30-minute drives on simple roads, alternating between driving while listening to an audiobook (dual-task) or single-task driving. Drivers did one drive with the simple and the other with the complex audiobook (order counterbalanced). Listening to the simple audiobook improved driving performance as compared to single-task driving: braking response times to hazards were lower, as were steering and headway variability. Conversely, listening to the complex audiobook interfered with driving; braking times to hazards and steering variability were higher when drivers were listening to the audiobook than for single-task driving. Individual differences in working memory capacity as measured by the OSPAN (Operation Span) predicted how much listening to an audiobook benefitted performance, with the highest OSPAN scorers benefitting most, though these OSPAN-related differential benefits were restricted to reduced hazard response times while listening to the simple audiobook.