Because of the demonstrated differences in sensitivity and diagnosticity, researchers should consider the use of cardiac measures in addition to driving performance measures when studying attention in a driving simulator environment.

Cardiac (heart rate, pre-ejection period, and respiratory sinus arrhythmia), performance, and visual demand measures of driver workload were obtained from 15 male university students who drove a simulated course multiple times at a fixed speed of 72.4 km/h. The course contained curves of 3 different radii (582, 291, and 194 m) and was driven with and without visual occlusion of the road scene to manipulate driver workload. Visual occlusion of the road scene significantly reduced driving performance but did not affect the cardiac measures. Driving performance significantly deteriorated and visual demand significantly increased as curve radius decreased. The cardiac measures were differentially affected by curve radius, indicating different modes of autonomic control for the 291-m curve as compared with the 582- and 194-m curves. The patterns of dissociation across the cardiac, performance, and visual demand measures were interpreted as being capable of isolating the perceptual demands of driving from the central and motor processing demands. A potential application of this research is that the combination of psychophysiological and visual occlusion methodologies are a powerful research tool to assess performance and processing resource cost trade-offs associated with using advanced in-vehicle technologies.

Summary: An autonomic space model of sympathetic and parasympathetic influences on the heart has been proposed as a method of deciphering psychological-physiological mappings for driving-related tasks. In the current study, we explore the utility of the autonomic space model for deciphering mappings in a driving simulation environment by comparing a single-task driving-only condition to two dual-task, driving-with-a-secondary-workingmemory task conditions. Although limited by a small sample size, the results illustrate the advantages physiological measures can have over performance measures for detecting changes in the psychological process required for drivingrelated task performance. Future research will include a repetition of this same study with more subjects as well the collection of on-the-road autonomic nervous system data.

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