Visually guided navigation: head-mounted eye-tracking of natural locomotion in children and adults

Abstract

The current study showed that visual fixation of obstacles is not required for rapid and adaptive navigation of obstacles. Children and adults wore a wireless, head-mounted eye-tracker during a visual search task in a room cluttered with obstacles. They spontaneously walked, jumped, and ran through the room, stepping up, down, and over obstacles. Both children and adults navigated adaptively without fixating obstacles, however, adults fixated less often than children. We discuss several possibilities for why obstacle navigation may shift from foveal to peripheral control over development.

Figure 1

Head-mounted eye-tracker. Top panels show a child wearing headgear, wireless transmitter, and battery supply. Bottom-left panel shows the image from the field of view camera with observer's gaze direction indicated by a red crosshair. Bottom-right panel shows the image from the eye camera.

Figure 2

Cluttered testing room from child's perspective. (B) Topographical map of room, drawn to scale. Impassable barriers are depicted in gray; traversable obstacles are colored according to obstacle height. Locations of star stickers are marked by blue stars.

Figure 3

Schematic diagram of footfalls leading to an encounter (A) up onto or down from an obstacle and (B) over an obstacle.

Figure 4

Mean fixation initiation and termination times for children and adults. Top panel shows fixation timing measured in seconds. Bottom panel shows fixation timing measured in steps.

Figure 5

Theoretical effects of height on the lower bound of the visual field for child and adult observers looking straight ahead. Heights are CDC 50th percentiles for 8-year-old girls and 20-year-old women. Gray rectangles represent 20-cm obstacles located 45 cm in front of the feet, visible to the child but not the adult.