Gaze and the Control of Foot Placement When Walking in Natural Terrain

TLDR

Human locomotion in natural environments requires precise coordination between bipedal gait biomechanics and eye movements, yet little is known about how the visual and locomotor systems collaborate to support movement through the world. We developed a system that simultaneously records gaze and full‑body kinematics while walking across diverse outdoor terrains. Walkers tune their gaze to the specific information needed for paths of varying complexity while maintaining a constant temporal look‑ahead window, allowing them to tailor an energetically optimal gait that balances efficiency with stable foot placement, thereby demonstrating that eye movements and locomotion are tightly integrated to manage energetic costs, environmental uncertainty, and informational demands. A video abstract is available.

Abstract

Human locomotion through natural environments requires precise coordination between the biomechanics of the bipedal gait cycle and the eye movements that gather the information needed to guide foot placement. However, little is known about how the visual and locomotor systems work together to support movement through the world. We developed a system to simultaneously record gaze and full-body kinematics during locomotion over different outdoor terrains. We found that not only do walkers tune their gaze behavior to the specific information needed to traverse paths of varying complexity but that they do so while maintaining a constant temporal look-ahead window across all terrains. This strategy allows walkers to use gaze to tailor their energetically optimal preferred gait cycle to the upcoming path in order to balance between the drive to move efficiently and the need to place the feet in stable locations. Eye movements and locomotion are intimately linked in a way that reflects the integration of energetic costs, environmental uncertainty, and momentary informational demands of the locomotor task. Thus, the relationship between gaze and gait reveals the structure of the sensorimotor decisions that support successful performance in the face of the varying demands of the natural world. VIDEO ABSTRACT.