The use of visual and nonvisual cues in updating the perceived position of the world during translation

During self-motion the perceived positions of objects remain fixed in perceptual space. This requires that their perceived positions are updated relative to the viewer. Here we assess the roles of visual and non-visual information in this spatial updating. To investigate the role of visual cues observers sat in an enclosed, immersive, virtual environment formed by six rear-projection screens. A simulated room was presented stereographically and shifted relative to the observer. A playing card, whose movement was phase-locked to the room, floated in front of the subject who judged if this card was displaced more or less than the room. Surprisingly, perceived stability occurred not when the card’s movement matched the room’s displacement but when perspective alignment was maintained and parallax between the card and the room was removed. The role of the complementary non-visual cues was investigated by physically moving subjects in the dark. Subjects judged whether a floating target was displaced more or less than if it were earth stable. To be judged as earth-stationary the target had to move in the same direction as the observer: more so if the movement was passive. We conclude that both visual and non-visual cues to self-motion and active involvement in the movement are simultaneously required for veridical spatial updating.