ABSTRACT
When sitting on a swing or in a rocking chair we seldom have difficulty knowing whether we are sitting upright or leaning at an angle. In these cases we are able to use both visual cues, such as vertical trees and light posts and horizontal fence tops, and non-visual cues, such as the perception of the pull of gravity. What happens if we must rely solely on nonvisual information? Anecdotal information from those who do find themselves in situations which lack visual cues, such as skiers in a whiteout or divers at depths where the only external cue is the direction their air bubbles move, suggests that we can find it very difficult to judge which way is up.
