The Interaction of Cognitive Load and Attention-Directing Cues in Driving Yi-Ching Lee, University of Illinois at Urbana-Champaign, Savoy, Illinois, John D. Lee and Linda Ng Boyle, University of Iowa, Iowa City, Iowa Objective: This study investigated the effect of a nondriving cognitively loading task on the relationship between drivers’ endogenous and exogenous control of attention. Background: Previous studies have shown that cognitive load leads to a withdrawal of attention from the forward scene and a narrowed field of view, which impairs hazard detection. Method: Posner’s cue-target paradigm was modified to study how endog- enous and exogenous cues interact with cognitive load to influence drivers’ attention in a complex dynamic situation. In a driving simulator, pedestrian crossing signs that predicted the spatial location of pedestrians acted as endogenous cues. To impose cogni- tive load on drivers, we had them perform an auditory task that simulated the demands of emerging in-vehicle technology. Irrelevant exogenous cues were added to half of the experimental drives by including scene clutter. Results: The validity of endogenous cues influenced how drivers scanned for pedestrian targets. Cognitive load delayed drivers’ responses, and scene clutter reduced drivers’ fixation durations to pedestrians. Cognitive load diminished the influence of exogenous cues to attract attention to irrelevant areas, and drivers were more affected by scene clutter when the endogenous cues were invalid. Conclusion: Cognitive load suppresses interference from irrelevant exogenous cues and delays endogenous orienting of attention in driving. Application: The complexity of everyday tasks, such as driving, is better captured experimentally in paradigms that rep- resent the interactive nature of attention and processing load. Address correspondence to Yi-Ching Lee, Human Factors Division, Institute of Aviation, University of Illinois at Urbana- Champaign, 1 Airport Road, Savoy, IL 61874; chinglee@illinois.edu. HUMAN FACTORS, Vol. 51, No. 3, June 2009, pp. 271-280. DOI: 10.1177/0018720809337814. Copyright © 2009, Human Factors and Ergonomics Society. INTRODUCTION Increasingly, manufacturers and after-market suppliers offer drivers in-vehicle information systems that promise increased productiv- ity, convenience, and mobility. These systems can also undermine driver safety, given the potential for driver distraction. In 2005, the U.S. Department of Transportation’s National Highway Traffic Safety Administration esti- mated that 10% of vehicles driven during day- light hours were by someone conversing on a wireless phone (Glassbrenner, 2005). More generally, drivers engaged in a distracting activ- ity an average of once every 6 min (McEvoy, Stevenson, & Woodward, 2006). A naturalistic driving study demonstrated that driver inatten- tion is the leading contributor to crashes and near-crashes, with inattentive drivers having 3 times the likelihood of a near-crash or crash as attentive drivers (Klauer, Dingus, Neale, Sudweeks, & Ramsey, 2006). Simulator experiments can complement nat- uralistic studies by identifying the mechanisms underlying the increased crash risk associated with driver distraction. For example, Strayer and Johnston (2001) examined the influence of several distracting activities on driving per- formance in a controlled environment. They observed that active engagement in cell phone conversations interfered with drivers’ ability to detect simulated traffic lights, but holding a cell phone or listening to books on tape did not. In a subsequent study, Strayer, Drews, and Johnston (2003) concluded that actively engaging in a secondary, nondriving task led to a withdrawal of attention from the forward scene, yielding a form of inattention blindness. In addition,