Attentional overload, stress, and simulated driving performance.

This study tests the hypothesis that driver stress is associated with performance impairment because stress-prone drivers are vulnerable to overload of attentional resources. Eighty young-adult subjects performed a simulated drive concurrently with a grammatical reasoning task, presented either visually or auditorily. Priority assigned to the 2 tasks was also manipulated. In general, the patterns of dual-task interference predicted by attentional resource theory were not found, although interference was apparent with the auditory reasoning task. Measures of vulnerability to driver stress and intrusive cognitions were related to impaired lateral control mainly when task demands were relatively low, contrary to the overload hypothesis. These data indicate that performance in this task paradigm is characterized by adaptive mobilization of effort to meet changing task demands. Stressed drivers adapted to high levels of demand fairly efficiently, but they may be at risk of performance impairment when the task requires relatively little active control. Advantages of the simulator approach are discussed.