Task-dependent gaze priorities in driving

Abstract

During complex visuo-motor tasks, gaze behavior is largely controlled by the current task [1]. However, it is unclear how gaze allocation is accomplished when confronted with multiple task demands, especially in dynamic and unpredictable environments, as in driving. This has been called the “scheduling problem”. One simple solution is to actively search the visual scene for potentially important information (e.g. pedestrians, other cars, lane centering) at regular intervals (round-robin strategy). Another is to weight search frequency by the importance of the sub-tasks, as in reward-based models of gaze allocation. Alternatively, participants might rely on attentional capture by salient events. To address this question, we manipulated the tasks demands of participants who drove in a virtual environment including other cars, pedestrians and urban scenery. While driving there are several concurrent sub-goals, including avoiding other cars, following a lead car, and avoiding pedestrians. We recorded and analyzed gaze behavior for these driving sequences. These data provide the ground truth for gaze allocation as well as unique traversals through the environment for use in simulations. We simulate gaze allocation as a high-level, object based scheduling problem where covert object searches are engaged at regular intervals. If the object is present onscreen, an overt fixation occurs. Simulations were run with a uniform distribution across object categories and using a round-robin strategy. We found neither to be a good predictor of gaze allocation. Weighting search frequency by participants' global fixation distributions provides a better fit and using fixation distributions for local scene context provides the best. If subjects' fixation distributions are proportional to task priority, we discuss how a task-based reinforcement-learning model may accomplish such gaze allocation. [1] Hayhoe, M., & Ballard, D. (2005). Eye movements in natural behavior. Trends in Cognitive Sciences, 9(4), 188–193.