User:Arr8050/Coriolis effect (perception)

For the effect studied in physics, see Coriolis effect.

In psychophysical perception, the Coriolis effect (also referred to as the Coriolis illusion or the vestibular Coriolis effect) is the misperception of body orientation due to head movement while under the effect of rotation, often inducing nausea. This effect comes about as the head is moved in contrary or similar motion with the body during the time of a spin. This goes on to affect the vestibular system, particularly the semicircular canals which are affected by the acceleration. This causes a sense of dizziness or nausea before equilibrium is restored after the head returns to a stabilized state. Crucially, this illusion is based entirely upon perception, and is largely due to conflicting signals between one's sight and one's perception of their body position or motion. Examples of situations where this can arise are circular acceleration and movement during a circular rotation.

There is also the pseudo-Coriolis effect (also referred to as the optokinetic pseudo-Coriolis effect), which takes place when there is no physical circular movement, only visual. Perceptually it feels the same as the Coriolis effect, being perceived as self motion inducing the same kind of nausea and often the cause of motion sickness.

History
Coriolis force was discovered by Gaspard-Gustave de Coriolis in 1832. By the end of the 19th century, Coriolis force had become a common phrase in meteorological literature. Coriolis force is classified as a fictitious force that is applied to objects that are in rotation. The term was first applied to perception by G. Schubert in 1954, where it was termed the vestibular Coriolis effect due to theory that it was being caused by the fictitious force being at work within the semicircular canals.

Causes and Effects
The physiological mechanism by which the effect occurs is all contained within the semicircular canals, as determined by head tilt. When rotating and tilting a person's head, the endolymphatic fluid within the canal may be subjected to the Coriolis force. This occurs when the motion as at a constant rate so that the fluid and the canals move at the same rate, causing the sensation of rotation to disappear. When interrupted by a head movement, the fluid will move at an angle, affecting the cupula, which will cause a perceived rotation that is not occurring.

This most often occurs when a person's head is moved out of alignment during a spin. If individuals are spinning to the left along their y-axis and then push their head forward, that will bring their heads out of alignment and make it subject to Coriolis force and resultant effect. The manifestation of this effect is that the individuals will feel like their heads are tilting to their left.

This can cause nausea, disorientation, and vomiting resulting from motion sickness. These feelings of discomfort arise in the body due to a variety of signals when the signals being sent by the vestibular system and visual system are not in agreement, i.e. the eyes may be telling the body that one is not moving, but the vestibular systems' fine-tuned senses are detecting and communicating the opposite.

Real world instances
The Coriolis effect is a concern for pilots and astronauts, where it can cause extreme disorientation. This happens as pilots turn or rotate their aircraft, while also turning their head. It has been noted as difficult to report, as oftentimes the sensation is difficult to describe. In extreme situations, this can cause the pilot to lose control of the aircraft. Due to the possible dangers of this, pilots are often trained physiologically, such as in a Bárány chair, to prepare for such circumstances, along with being trained to trust their flying instruments rather than their own visual perceptions.

The pseudo-Coriolis effect often occurs in VR simulations, where it can be perceived that motion is occurring without the body itself moving.

See also[edit]

 * Dizziness
 * Equilibrioception
 * Sensory illusions in aviation

References[edit]

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Further reading[edit]
See, for example, Pouly and Young.