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Abstract

Spatial navigation in the presence of gravity ascribes one’s displacement to a 2D surface where only the yaw rotation has to be considered. In contrast, in weightlessness one is allowed to use the three rotations of space. In the present study, we investigated the influence of three different kinds of displacements on the ability to build a mental representation of a 3D corridor. Each of the displacements used a different set of rotations at junctions between segments, suggesting a different reference frame: the weightless condition used the unique rotation (among the three rotations of space) orienting the line of sight parallel to the next segment; the subaquatic condition functioned similarly to the previous one, but after going up or down a roll rotation would be added in order to reorient the head horizontally; the terrestrial condition maintained subjects’ heads horizontal all along the trajectory, going up and down facing the walls like in an elevator. The results showed that the terrestrial condition allows a better recall of the mental representation built while exploring, and that the weightless condition had the worst performance, suggesting that human cognitive functions are specialised for 2D navigation and not appropriate for weightless exploration.