How visual context influences lateral stepping regulation while walking on winding paths.

Goal-directed walking involves regulating foot placements to achieve specific tasks. This requires visuomotor integration. Perceptual, cognitive, and contextual salience guide attention and motor planning for navigation. Here, we quantified how perceptual salience informs lateral foot placement while walking. Participants walked along prescribed virtual paths (straight or winding), thus keeping contextual salience (the task itself) constant. We manipulated perceptual salience by systematically altering environment richness (rich vs. sparse) and path color contrast (high vs. low). We quantified head pitch angle to approximate gaze direction. We quantified lateral stepping regulation from a goal equivalent manifold framework. Our guiding hypothesis was that stepping arises from continuous decision-making action-perception processes: each step taken affects the decision of where to step next. This generated three testable predictions. First, that contextual salience alone (merely "seeing" the path) is sufficient for people to regulate stepping. However, while substantial between-path differences largely supported this, within-path differences in both head angle and stepping demonstrated that visual information (perceptual salience) also informs stepping. Second, we predicted perceptual salience of task-relevant visual information (here, of the path itself) is sufficient to guide stepping. However, while changing path color contrast did elicit more and greater changes than manipulating environmental richness, path visual saliency alone was not sufficient. Third, we predicted perceptual salience from peripheral vision also contributes to stepping. This prediction was supported, though less strongly than manipulating path visual saliency or contextual salience (straight vs. winding paths). Thus, both contextual and perceptual salience interact to influence step-to-step control of walking.