Action strategies for walking through multiple, misaligned apertures

When avoiding obstacles, path selection is thought to be determined by the attraction of the end-goal. However for aperture crossing, it is unclear whether the attraction point originates in the center of the aperture or at the end-goal, as previous experiments align the aperture with the end-goal. The purpose of the current study was to decipher the possible location of the attraction point, by evaluating crossing behaviour for multiple, misaligned apertures. Participants were instructed to walk through three separate apertures while en route to an end-goal. The first and last apertures were fixed such that they were both either 0.9× or 1.7× shoulder width (SW) while the second aperture was either 0.9, 1.3 or 1.7× SW and shifted 25, 50 or 75cm off the midline. Findings revealed that the attraction of the end-goal, and not the middle of the aperture, guided crossing behaviour. The spatial margin decreased as the size of the shift increased. Furthermore, the frequency of rotation increased as the aperture was shifted away from midline, regardless of the aperture size. Since rotations would not normally occur for all of these aperture sizes when aligned with the end-goal, these results suggest that rotations were produced in an attempt to keep one's trajectory as close to the midline as possible. Therefore, not only does the attraction of the goal guide path trajectory, but individuals will choose to reduce the spatial margin and rotate the shoulders when walking through misaligned apertures, likely in attempt to maintain the straightest possible path.