A Case Study of Human Roll Tilt Perception in Hypogravity

Area of Science:

• Human perception
• Gravitational effects on physiology
• Aerospace medicine

Background:

• Humans overestimate roll tilt in hypergravity (high G), known as the "G-excess" illusion.
• A modified observer model predicted underestimation of roll tilt in hypogravity (low G).

Purpose of the Study:

• To test the prediction of underestimating roll tilt in hypogravity.
• To investigate human orientation perception in altered gravitational environments.

Main Methods:

• A single subject performed a subjective visual vertical task during aircraft parabolic flight.
• Roll tilt perception was assessed in hypogravity (0.165 G, 0.38 G), hypergravity (1.6 G, 1.2 G), and 1-G control conditions.

Main Results:

• The subject significantly underestimated roll tilt in hypogravity by ~40% compared to 1-G.
• Roll tilt was overestimated in hypergravity conditions, consistent with the "G-excess" illusion.

Conclusions:

• The observed underestimation in hypogravity aligns with the modified observer model's predictions.
• The
• G-shortage
• illusion is proposed for hypogravity roll tilt underestimation.
• Findings have implications for pilots and astronauts operating in varying gravity.