An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain While illusions distort reality, they are generally shared by most people. ^[1] Illusions may occur with more of the human senses than vision, but visual illusions, optical illusions, are the most well known and understood. Senses are the physiological methods of Perception. The senses and their operation classification and theory are overlapping topics studied by a variety of fields This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album The emphasis on visual illusions occurs because vision often dominates the other senses. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also For example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words. ^[2] Some illusions are based on general assumptions the brain makes during perception. In Psychology and the Cognitive sciences perception is the process of attaining awareness or understanding of sensory Information. These assumptions are made using organizational principles, like Gestalt, an individual's ability of depth perception and motion perception, and perceptual constancy. Depth perception is the visual ability to perceive the world in three Dimensions Although any animal capable of moving around its environment must be able to Other illusions occur because of biological sensory structures within the human body or conditions outside of the body within one’s physical environment. The human body is the entire physical and mental structure of a Human Organism.

The term illusion refers to a specific form of sensory distortion. Unlike a hallucination, which is a distortion in the absence of a stimulus, an illusion describes a misinterpretation of a true sensation. A hallucination, in the broadest sense is a Perception in the absence of a stimulus. For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water (or other auditory source) would be an illusion.

Mimes are known for a repertoire of illusions that are created by physical means. The mime artist creates an illusion of acting upon or being acted upon by an unseen object. These illusions exploit the audience's assumptions about the physical world. Well known examples include "walls", "climbing stairs", "leaning", "descending ladders", "pulling and pushing" etc.

Optical illusions

An optical illusion. Square A is exactly the same shade of grey as Square B. See Same color illusion

Main article: Optical illusion

An optical illusion is always characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. The same color illusion — also known as Adelson's checker shadow illusion, checker shadow illusion and checker shadow — is an Optical illusion This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. A perception is a philosophical term which roughly means an individual's observation/perception of something external to one's self more specifically the resultant of perceiving A conventional assumption is that there are physiological illusions that occur naturally and cognitive illusions that can be demonstrated by specific visual tricks that say something more basic about how human perceptual systems work. The human brain constructs a world inside our head based on what it samples from the surrounding environment. However sometimes it tries to organise this information it thinks best while other times it fills in the gaps. This way in which our brain works is the basis of an illusion.

Auditory illusions

Main article: Auditory illusion

An auditory illusion is an illusion of hearing, the sound equivalent of an optical illusion: the liner hears either sounds which are not present in the stimulus, or "impossible" sounds. An auditory illusion is an Illusion of hearing, the aural equivalent of an optical illusion the listener hears either sounds which are not present in the stimulus An auditory illusion is an Illusion of hearing, the aural equivalent of an optical illusion the listener hears either sounds which are not present in the stimulus Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies In short, audio illusions highlight areas where the human ear and brain, as organic, makeshift tools, differ from perfect audio receptors (for better or for worse). One of example of an auditory illusions is a Shepard tone. A Shepard tone, named after Roger Shepard, is a Sound consisting of a superposition of sine waves separated by Octaves When played with the base

Tactile illusions

Main article: Touch illusion

Examples of tactile illusions include phantom limb, the thermal grill illusion, the cutaneous rabbit illusion and a curious illusion that occurs when the crossed index and middle fingers are run along the bridge of the nose with one finger on each side, resulting in the perception of two separate noses. Touch illusions are Illusions that exploit the Sense of touch. A phantom limb is the sensation that an amputated or missing limb (even an organ like the appendix is still attached to the body and is moving appropriately The thermal grill illusion is a sensory Illusion originally demonstrated in 1896 by T The cutaneous rabbit illusion (also known as cutaneous saltation is a tactile illusion evoked by tapping two separate regions of the skin Interestingly, the brain areas activated during illusory tactile perception are similar to those activated during actual tactile stimulation^[3]. Tactile illusions can also be elicited through haptic technology^[4]. These "illusory" tactile objects can be used to create "virtual objects"^[5]

Other senses

Illusions can occur with the other senses including that of taste and smell. It was discovered that even if some portion of the taste receptor on the tongue became damaged that illusory taste could be produced by tactile stimulation. ^[6]. Evidence of olfactory (smell) illusions occurred when positive or negative verbal labels were given prior to olfactory stimulation^[7]. Olfaction (also known as olfactics or smell) refers to the Sense of smell.

Disorders

Some illusions occur as result of an illness or a disorder. While these types of illusions are not shared with everyone they are typical of each condition. For example migraine suffers often report Fortification illusions. Scintillating scotoma is the most common visual aura preceding Migraine and was first described by 19th century physician Hubert Airy (1838–1903

References

• Yoon Mo Jung and Jackie (Jianhong) Shen (2008), J. Visual Comm. Image Representation, 19(1):42-55, First-order modeling and stability analysis of illusory contours.

See also

• Augmented reality for a more radical approach to the possibility of illusion
• Delusion
• Dream argument
• Simulated reality
• Best Rotating Illusions Video
• Make own Illusion video

External links

• Illusion Database Daily Illusions
• What is an Illusion? by J. Augmented reality ( AR) is a field of Computer research which deals with the combination of real-world and computer-generated data A delusion is commonly defined as a fixed False Belief and is used in everyday language to describe a belief that is either false fanciful or derived from Deception The "dream argument" is the postulation that the act of dreaming provides preliminary evidence that the senses we trust to distinguish reality from illusion should not be fully Simulated reality is the proposition that Reality could be simulated—perhaps by Computer simulation —to a degree indistinguishable from "true" Reality R. Block.
• Optical illusions and visual phenomena by Michael Bach
• Auditory illusions
• Haptic Perception of Shape - touch illusions, forces and the geometry of objects, by Gabriel Robles-De-La-Torre.
• Illusions of taste