Gravity cue has implicit effects on human behavior.

Gravity modifies us without our knowing it. Possible functional disabilities of eye, head and body movements were investigated under 1 G and microgravity environments to evaluate the gravity cue for human behavior. The system for visual stability might be explained from the viewpoint of ordination between eye and head under microgravity. It is important ascertain the significance of gravity in the maintenance of human visual stability. Coordination of eye position and head motion behavior by neck muscle discharge was examined in the mission SL-J, as well as a subjective evaluation of visual stability during spaceflight. The results shows that: 1) poor performance of eye movement can be observed; 2) unusual neck muscle activity can be observed; 3) there is decreased visual stability in microgravity; and 4) egocentric body axis is emphasized under microgravity conditions.