ABSTRACT
Visually-induced self-motion and postural reflexes were first explored in weightlessness on the Spacelab 1 mission where four subjects demonstrated that visual orientation effects were stronger in weightlessness than pre-flight. Extended testing of two more subjects during the Spacelab D–1 orbital flight confirmed this finding. The development of visual substitution for inappropriate graviceptor information occurs over the first day or two in weightlessness. Additional instrumentation to measure head and body postural reactions failed to produce a more reliable indicator of visual effects than subjective orientation. Localized tactile cues applied to the feet in all cases changed the qualitative nature of vection and reduced its strength.
