Which of the following accurately identifies the two vestibular illusions?

• A. Somatogyral and Coriolis
• B. The Leans and Graveyard Spin
• C. Visual illusions
• D. Somatogyral and Somatogravic

Answer: (D)

In flight, sensory information from the inner ear can mislead you when it doesn’t match what you see. The two main vestibular illusion types are somatogyral and somatogravic. Somatogyral illusions come from angular motion about the head or aircraft axes; the semicircular canals respond to rotation and can create a false sense of turning or tilting even when you’re level, especially after unusual or sustained rotations. Somatogravic illusions come from linear acceleration; the otolith organs respond to forward or backward acceleration and gravity, which can make you feel nose-up or nose-down during rapid pitch changes, takeoff, or braking. These two categories cover the primary ways the vestibular system can produce illusory motion or orientation.

Visual illusions exist too, but they’re not vestibular. Specific examples like the Leans or Graveyard Spin are real manifestations of vestibular misperception, and they fall under the broader somatogyral effects, but the two fundamental vestibular illusion categories you’re being asked to identify are somatogyral and somatogravic.