Gaze behavior during locomotion through apertures: the effect of locomotion forms.

The present study investigated spatio-temporal patterns of gaze fixations for passing safely through apertures. We focused on whether fixation patterns changed in response to changes in locomotion forms. Eight participants approached and passed through a narrow doorway using the following locomotion forms: normal walking, walking while holding a 63-cm horizontal bar with or without shoulder rotations permitted, and wheelchair use (63 cm wide). All participants were naïve to wheelchair use. The results showed that the fixation patterns were dependent on whether the locomotion form was walking or wheelchair use. In the three walking conditions, fixations were almost evenly directed toward the aperture and door edges at first; however, in the final phase, fixations were exclusively directed toward the center of the aperture. In contrast, in the wheelchair condition, fixations were directed more frequently toward the door edges throughout locomotion. These findings demonstrate that spatial-temporal patterns of fixation remain unchanged during walking through apertures, irrespective of the constraints on movement. The observed fixation patterns indicate that individuals appear to rely on optic flow to guide locomotion. However, the patterns of fixation are altered when they involve a completely novel task of locomotion, such as when using a wheelchair for the first time.