Effects of cognitive load on driving performance: The cognitive control hypothesis

Objective: The main objective of this paper was to outline an explanatory framework for understanding effects of cognitive load on driving performance and to review the existing experimental literature in the light of this framework. Background: While there is general consensus that taking the eyes off the forward roadway significantly impairs most aspects of driving, the effects of primarily cognitively loading tasks on driving performance are not well understood. Method: Based on existing models of driver attention, an explanatory framework was outlined. This can be summarized in terms of the cognitive control hypothesis: Cognitive load selectively impairs driving sub-tasks that rely on cognitive control but leaves automatic performance unaffected. An extensive literature review was conducted where existing results were re-interpreted based on the proposed framework. Results: It was demonstrated that the general pattern of experimental results reported in the literature aligns well with the cognitive control hypothesis and that several apparent discrepancies between studies can be reconciled based on the proposed framework. More specifically, performance on non-practiced or inherently variable tasks, relying on cognitive control, is consistently impaired by cognitive load while the performance on automatized (well-practiced and consistently mapped) tasks is unaffected and sometimes even improved. Conclusion: Effects of cognitive load on driving are strongly selective and task-dependent. Application: The present results have important implications for the generalization of results obtained from experimental studies to real world driving. The proposed framework can also serve to guide future research on the potential causal role of cognitive load in real-world crashes.