Eye Movement Patterns during Locomotion in Real-World and Simulated Environments

Eye movements in a search-and-count walking task were compared between a simulated (SE) and real-world environment (RE). Eye movements were recorded using the mobile WearCam in either RE or the StroMoHab locomotion simulator, a treadmill-based system for gait mobility rehabilitation. For Experiment 1, a RE was prepared with objects (coloured balls) and occluding barriers placed along a 38 m long corridor. A video was captured from a walker's viewpoint at 1.3 km/hr. Fifteen subjects per environment reported the total object count after completing a walk while viewing the video in the SE (at 0, 1.3, or 2.5 km/h) and RE (at 1.3 km/h). Examining the number of eye transitions (TotET) between objects in relation to walking speed in SE, revealed significant increases between 0 and 2.5 km/h ( F 3, 56 =20.62, p = .02) and 1.3 and 2.5 km/h ( F 3, 56 =20.62, p = .039), despite no change in video speed; no significant difference was found between 0 and 1.3 km/h. In Experiment 2, 15 subjects viewed a static checkered screen and were instructed to ‘view the screen’ while walking. TotET decreased significantly, between 1.3 km/h and 5.2 km/h ( F 2, 27 =3.437, p = .014); no significant differences were observed between 2.6 km/h and either 1.3 km/h or 5.2 km/h. In real-world conditions, walking faster increases the difficulty of search tasks, with a likely correlated increase in eye movements. Apparently, the expectation of increased difficulty carries over to SE, even if the visual task is not more difficult. The findings point to physiological and perceptual correlations between locomotion and eye movements.