Motives driving gaze and walking decisions.

To navigate complex environments, people must decide how to direct gaze to acquire relevant information and decide where, when, and how to move the body. Recent work supports the idea that gaze may be directed to reduce task-relevant environmental uncertainty and to ensure movement accuracy based on the cost (or effort) to move the body and maintain balance. During walking, these two factors may compete for gaze allocation and explain how we make decisions about where to step. Using a forced-choice walking paradigm, where we manipulated the visual uncertainty (simulating uncertain terrain characteristics) and motor cost associated with specific step-target choices, we examined the motives driving gaze and step decisions. We characterized each individual's distinct gaze behavior based on their sensitivity to changes in visual uncertainty, which predicted step-choice behavior when foot-placement accuracy was important to the task. We show that individuals who tended to look at both target choices as visual uncertainty increased prioritized stepping onto the more certain location after looking at it longer, even at the expense of increased motor cost. In contrast, individuals who tended to look at only one of the target choices as visual uncertainty increased preferred to step on the target that minimized motor cost. Overall, we demonstrate that how a person explores the environment with their eyes dictates where they step. These gaze and step decisions may relate to the value a person assigns to information gain, being certain of their actions, and conserving energy.