Illusions of self-motion (or "vection") occur when one perceives bodily motion despite no movement taking place. One can experience illusory movements of the whole body or of individual body parts, such as arms or legs.
Illusions of self-motion (or "vection") occur when one perceives bodily motion despite no movement taking place. One can experience illusory movements of the whole body or of individual body parts, such as arms or legs.
The vestibular system is one of the major sources of information about one's own motion. Disorders of the visual system can lead to dizziness, vertigo, and feelings of instability. Vertigo is not associated with illusory self-motion as it does not typically make one feel as though they are moving; however, in a subclass of vertigo known as subjective vertigo one does experience their own motion. People experience themselves being pulled heavily in one direction. [2] There are also specific self-motion illusions that can occur through abnormal stimulation of various parts of the vestibular system, often encountered in aviation. This includes an illusion of inversion, in which one feels like they're tumbling backwards. Through various stimuli, people can be made to feel as if they are moving when they are not, not moving when they are, tilted when they are not, or not tilted when they are. [3]
When a large part of the visual field moves, viewers feel like they have moved and that the world is stationary. [4] For example, when one is in a train at a station, and a nearby 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 center 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 their line of sight. During circular vection, the observer feels like they are rotating and the drum is stationary. During linear vection, the observer feels like they have moved forwards or backwards and the stimulus has stayed stationary. During roll vection, the observer feels like they have rotated around the line of sight and the disk has stayed stationary.
Inducing vection can also induce motion sickness in susceptible individuals.
Compared to visually-induced vection, auditorily-induced vection is generally weaker. Auditory-induced vection can only be elicited in about 25% to 75% of the participants under laboratory conditions, and only when participants are blindfolded. [1] Most of the research has focused on eliciting circular vection horizontally about the body. Researchers have induced circular vection by mechanically rotating a buzzer around a subject in the dark or by presenting sound sequentially in one of several speakers arranged in a circular array. [5] Adding auditory stimuli can significantly enhance visual, vestibular, and biomechanical vections. [1]
After being on a small boat for a few hours and then going back onto land, it may feel like there is still rising and falling, as if one is still on the boat. [6] It can also occur on other situations, such as after a long journey by train or by aircraft, or after working up a swaying tree. It is not clear whether sea legs are a form of aftereffect to the predominant frequency of the stimulation (e.g., the waves or the rocking of the train), whether it is a form of learning to adjust one's gait and posture.[ citation needed ] The "sea legs" condition needs to be distinguished from mal de debarquement, which is much more long-lasting.
Linear treadmills by themselves generally do not induce illusions of self-motion. However, subjects report a strong sense of self-rotation from stepping along a circular treadmill in the dark, which can be further enhanced through auditory cues. [1]
An illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people.
A tactile illusion is an illusion that affects the sense of touch. Some tactile illusions require active touch, whereas others can be evoked passively. In recent years, a growing interest among perceptual researchers has led to the discovery of new tactile illusions and to the celebration of tactile illusions in the popular science press. Some tactile illusions are analogous to visual and auditory illusions, suggesting that these sensory systems may process information in similar ways; other tactile illusions don't have obvious visual or auditory analogs.
Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include nausea, vomiting, cold sweat, headache, dizziness, tiredness, loss of appetite, and increased salivation. Complications may rarely include dehydration, electrolyte problems, or a lower esophageal tear.
The sense of balance or equilibrioception is the perception of balance and spatial orientation. It helps prevent humans and nonhuman animals from falling over when standing or moving. Equilibrioception is the result of a number of sensory systems working together; the eyes, the inner ears, and the body's sense of where it is in space (proprioception) ideally need to be intact.
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear in most mammals.
Spatial disorientation is the inability to determine position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular system, and proprioceptive system collectively work to coordinate movement with balance, and can also create illusory nonvisual sensations, resulting in spatial disorientation in the absence of strong visual cues.
The autokinetic effect is a phenomenon of visual perception in which a stationary, small point of light in an otherwise dark or featureless environment appears to move. It was first recorded in 1799 by Alexander von Humboldt who observed illusory movement of a star in a dark sky, although he believed the movement was real. It is presumed to occur because motion perception is always relative to some reference point, and in darkness or in a featureless environment there is no reference point, so the position of the single point is undefined. The direction of the movements does not appear to be correlated with involuntary eye movements, but may be determined by errors between eye position and that specified by efference copy of the movement signals sent to the extraocular muscles. Richard Gregory suggested that, with lack of peripheral information, eye movements which correct movements due to muscle fatigue are wrongly interpreted as movement of the perceived light.
Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. This can occur with turning in bed or changing position. Each episode of vertigo typically lasts less than one minute. Nausea is commonly associated. BPPV is one of the most common causes of vertigo.
The term illusory motion, also known as motion illusion or "apparent motion", is an optical illusion in which a static image appears to be moving due to the cognitive effects of interacting color contrasts, object shapes, and position. The stroboscopic animation effect is the most common type of illusory motion and is perceived when images are displayed in fast succession, as occurs in movies. The concept of illusory motion was allegedly first described by Aristotle.
The wagon-wheel effect is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation.
The Ehrenstein illusion is an optical illusion of brightness or colour perception. The visual phenomena was studied by the German psychologist Walter H. Ehrenstein (1899–1961) who originally wanted to modify the theory behind the Hermann grid illusion. In the discovery of the optical illusion, Ehrenstein found that grating patterns of straight lines that stop at a certain point appear to have a brighter centre, compared to the background.
Vertigo is a condition in which a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. It may be associated with nausea, vomiting, perspiration, or difficulties walking. It is typically worse when the head is moved. Vertigo is the most common type of dizziness.
In human perception, contingent aftereffects are illusory percepts that are apparent on a test stimulus after exposure to an induction stimulus for an extended period. Contingent aftereffects can be contrasted with simple aftereffects, the latter requiring no test stimulus for the illusion/mis-perception to be apparent. Contingent aftereffects have been studied in different perceptual domains. For instance, visual contingent aftereffects, auditory contingent aftereffects and haptic contingent aftereffects have all been discovered.
The otolithic membrane is a fibrous structure located in the vestibular system of the inner ear. It plays a critical role in the brain's interpretation of equilibrium. The membrane serves to determine if the body or the head is tilted, in addition to the linear acceleration of the body. The linear acceleration could be in the horizontal direction as in a moving car or vertical acceleration such as that felt when an elevator moves up or down.
The barberpole illusion is a visual illusion that reveals biases in the processing of visual motion in the human brain. This visual illusion occurs when a diagonally striped pole is rotated around its vertical axis (horizontally), it appears as though the stripes are moving in the direction of its vertical axis rather than around it.
The sopite syndrome is a neurological disorder that relates symptoms of fatigue, drowsiness, and mood changes to prolonged periods of motion. The sopite syndrome has been attributed to motion-induced drowsiness such as that experienced by a baby when rocked. Researchers Ashton Graybiel and James Knepton at the US Naval Aerospace Medical Research Laboratory first used the term "the sopite syndrome" in 1976, to refer to the sometimes sole manifestation of motion sickness, though other researchers have referred to it as "Sopite syndrome."
Vertiginous epilepsy is infrequently the first symptom of a seizure, characterized by a feeling of vertigo. When it occurs, there is a sensation of rotation or movement that lasts for a few seconds before full seizure activity. While the specific causes of this disease are speculative there are several methods for diagnosis, the most important being the patient's recall of episodes. Most times, those diagnosed with vertiginous seizures are left to self-manage their symptoms or are able to use anti-epileptic medication to dampen the severity of their symptoms.
The righting reflex, also known as the labyrinthine righting reflex, is a reflex that corrects the orientation of the body when it is taken out of its normal upright position. It is initiated by the vestibular system, which detects that the body is not erect and causes the head to move back into position as the rest of the body follows. The perception of head movement involves the body sensing linear acceleration or the force of gravity through the otoliths, and angular acceleration through the semicircular canals. The reflex uses a combination of visual system inputs, vestibular inputs, and somatosensory inputs to make postural adjustments when the body becomes displaced from its normal vertical position. These inputs are used to create what is called an efference copy. This means that the brain makes comparisons in the cerebellum between expected posture and perceived posture, and corrects for the difference. The reflex takes 6 or 7 weeks to perfect, but can be affected by various types of balance disorders.
Fred W. Mast is a full professor of Psychology at the University of Bern in Switzerland, specialized in mental imagery, sensorimotor processing, and visual perception. He directs the Cognitive Psychology, Perception, and Research Methods Section at the Department of Psychology of the University of Bern.
Simulator sickness is a subset of motion sickness that is typically experienced while playing video games from first-person perspective. It was discovered in the context of aircraft pilots who undergo training for extended periods of time in flight simulators. Due to the spatial limitations imposed on these simulators, perceived discrepancies between the motion of the simulator and that of the vehicle can occur and lead to simulator sickness. It is similar to motion sickness in many ways, but occurs in simulated environments and can be induced without actual motion. Symptoms of simulator sickness include discomfort, apathy, drowsiness, disorientation, fatigue, and nausea. These symptoms can reduce the effectiveness of simulators in flight training and result in systematic consequences such as decreased simulator use, compromised training, ground safety, and flight safety. Pilots are less likely to want to repeat the experience in a simulator if they have suffered from simulator sickness and hence can reduce the number of potential users. It can also compromise training in two safety-critical ways: