Illusions of self-motion occur when one moves or feels one has moved without feeling that one has made the movement. Motions can include movements of the whole body or movements of single limbs. Illusions include vestibular illusions, vection, sea legs, the ideomotor effect, and alien hand syndrome.

Vestibular illusions

The vestibular system

Vestibular system

The vestibular system, which contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of...

 is one of the major sources of information about one's own motion. Disorders of the visual system can lead to dizziness

Dizziness

Dizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....

, vertigo

Vertigo (medical)

Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...

, and feelings of instability. There are also specific self-motion illusions that can occur through abnormal stimulation of various parts of the vestibular system. These include vestibular/somatogyral Illusions and vestibular/somatogravic Illusions in aviation. These are described in Sensory illusions in aviation

Sensory Illusions in Aviation

Because human senses are adapted for use on the ground, navigating by sensory input alone during flight can be dangerous: sensory input does not always accurately reflect the movement of the aircraft, causing sensory illusions. These illusions can be extremely dangerous for pilots.-Vestibular...

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Vection

When a large part of the visual field moves, a viewer feels they have moved and that the world is stationary. For example, when one is in a train at a station, and another neighbouring train moves, one can have the illusion that one's own train has moved in the opposite direction. Common sorts of vection include circular vection, where an observer is placed at the centre of rotation of a large vertically oriented, rotating drum, usually painted with vertical stripes, linear vection, where an observer views a field that either approaches or recedes, and roll vection, where an observer views a patterned disk rotating around his or her line of sight. During circular vection, the observer feels they are rotating and the drum is stationary, during linear vection, the observer feels they have moved forwards or backwards and the stimulus has stayed stationary, and during roll vection, the observer feels they have rotated around the line of sight and the disk has stayed stationary.

Inducing vection can also induce motion sickness

Motion sickness

Motion sickness or kinetosis, also known as travel sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement...

 in susceptible individuals.

Sea legs, or dock rock

After being on a small boat for a few hours, when one comes back onto land, one may feel that one is still rising and falling as if still on the boat. It can also occur on other situations, such as after a long train journey. It is not clear whether sea legs is a form of aftereffect to the predominant frequency of the stimulation (e.g., of the waves or the rocking of the train), whether it is a form of learning to adjust one's gait

Gait

Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency...

 and posture

Human position

Human positions refers to the different positions that the human body can take.There are several synonyms that refer to the human position, often used interchangeably, but having specific flavors....

, or whether it is a form of the Tetris effect

Tetris effect

The Tetris effect occurs when people devote sufficient time and attention to an activity that it begins to overshadow their thoughts, mental images, and dreams...

. Sea legs needs to be distinguished from mal de debarquement

Mal de debarquement

Mal de debarquement syndrome is a rare condition usually occurring after a cruise, aircraft flight, or other sustained motion event. It has only recently received attention and very little real scientific research has been conducted...

, which is much more disturbing and long-lasting.

Ideomotor effect

The ideomotor effect

Ideomotor effect

The ideomotor effect is a psychological phenomenon wherein a subject makes motions unconsciously. As in reflexive responses to pain, the body sometimes reacts reflexively to ideas alone without the person consciously deciding to take action. For instance, tears are produced by the body...

 is when someone moves voluntary muscles without being aware of doing so. One example is in moving the planchette

Planchette

A planchette , from the French for "little plank", is a small, usually heart-shaped flat piece of wood that one moves around on a board to spell out messages or answer questions. Paranormal advocates believe that the planchette is moved by some extra-normal force. The motion is due to the...

 on an Ouija board

Ouija Board

Ouija Board is a Thoroughbred mare racehorse owned by Edward Stanley, 19th Earl of Derby and trained by Ed Dunlop. In a career spanning four seasons, she won 10 of her 22 races, 7 of them Group 1s, including the Epsom Oaks in 2004 and the Hong Kong Vase in 2005...

. There are at least two theories. One is that an unconscious consensus guides all the individuals to make similar, very slight movements, none of which are enough to be conscious in any individual, but together make it seem that the planchette is under external control. The other is that the consensus emerges from the sum of the various unconscious movements made by the participants, and that once this motor consensus begins to be established, it recruits confirming slight movements in each participant, again less than is conscious to any individual.

Other examples include automatic writing

Automatic writing

Automatic writing or psychography is writing which the writer states to be produced from a subconscious and/or spiritual source without conscious awareness of the content.-History:...

, dowsing

Dowsing

Dowsing is a type of divination employed in attempts to locate ground water, buried metals or ores, gemstones, oil, gravesites, and many other objects and materials, as well as so-called currents of earth radiation , without the use of scientific apparatus...

, and facilitated communication

Facilitated communication

Facilitated communication is a process by which a facilitator supports the hand or arm of a communicatively impaired individual while using a keyboard or other devices with the aim of helping the individual to develop pointing skills and to communicate...

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Alien hand syndrome

Alien hand syndrome

Alien hand syndrome

Alien hand syndrome is a neurological disorder in which the afflicted person's hand appears to take on a mind of its own...

 occurs when an individual makes a movement of one part of their body without being aware of it. It is usually associated with different sorts of brain damage

Brain damage

"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...

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