Illusion
An illusion is a distortion of the
Illusions may occur with any of the human senses, but visual illusions (
Some illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles (e.g., Gestalt theory), an individual's capacity for depth perception and motion perception, and perceptual constancy. Other illusions occur due to biological sensory structures within the human body or conditions outside the body within one's physical environment.
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. For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water (or another auditory source) would be an illusion. So, it should not be wrong to consider that illusions are just "misinterpretations" on how our brain perceives something that exists (unlike a hallucination where a stimulus is absent).
Visual
A
The visual system, which includes the eyes (namely the retinas) and the central nervous system (namely the brain's visual cortex), constructs reality through both perceptual and cognitive neural pathways. Visual illusions are (at least in part) thought to be caused by excessive competing stimuli. Each stimulus follows a dedicated neural path in the early stages of visual processing, and intense/repetitive activity or interaction with active adjoining channels (perceptual neural circuits, usually at the same level) causes a
The assembly of visual elements into a collective percept, that distinguishes objects from backgrounds, takes part during intermediate-level visual processing. Many common visual illusions are a consequence of the percept constructed during this processing stage, as the elements first captured during low-level processing might easily be interpreted to form an image that differs from objective reality. An example is when two objects of the same size are placed on a certain background which conditions us to believe that one object might be larger than the other, and when the background is removed or replaced our perception immediately changes to the correct scenario (effectively concluding that both objects have equal dimensions).[4]
High-level visual processing consolidates information gathered from various sources to apply cognitive influences that create a conscious visual experience. Thus, allowing us to recognize the complex identity of different elements, and the disparate relations between them through cognitive processes. Visual illusions are also often a product of this processing stage, and it is during this stage that we might ultimately become conscious of any optical illusion. There are two crucial properties of our visual system related mostly to high-level visual processing, referred to as selectivity and invariance (which we have consistently attempted to replicate in image recognition computer algorithms). Selectivity refers to the identification of particular features that are relevant to recognize a specific element or object, while abstracting from other features that are not fundamental to performing the same recognition (e.g. when we see the shape of a house, certain contours that are essential for us to recognize it while other contours or image properties are not, such as color). On the other hand, invariance refers to the ability to be indifferent to small variations of a given feature, effectively identifying all those variations as simply being different versions of the same feature (e.g. we can recognize a given handwritten letter of the alphabet, written by different people with distinct styles of calligraphy).[4]
The whole process that constructs our visual experience is extremely complex (with multiple qualities that are unmatched by any computer or digital system). It is organized by many sequential and parallel sub-processes, each of which is essential in building our conscious image of the world. Our whole visual system seeks to simplify and categorize the unstructured low-level visual information, through both selectivity and invariance. Thus, while trying to organize an image by "filling in the gaps" through assumptions, we become vulnerable to misinterpretation.[5][6]
Auditory
An auditory illusion is an illusion of
Tactile
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. The brain areas activated during illusory tactile perception are similar to those activated during actual tactile stimulation.[7] Tactile illusions can also be elicited through haptic technology.[8] These "illusory" tactile objects can be used to create "virtual objects".[9]
Temporal
A temporal illusion is a distortion in the perception of time, which occurs when the time interval between two or more events is very narrow (typically less than a second). In such cases, a person may momentarily perceive time as slowing down, stopping, speeding up, or running backward.
Intersensory
Illusions can occur with the other senses including those involved in food perception. Both sound
Disorders
Some illusions occur as a 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, people with migraines often report
Neuroscience
Perception is linked to specific brain activity and so can be elicited by brain stimulation. The (illusory) percepts that can be evoked range from simple phosphenes (detections of lights in the visual field) to high-level percepts.[15] In a single-case study on a patient undergoing presurgical evaluation for epilepsy treatment, electrical stimulation at the left temporo-parietal junction evoked the percept of a nearby (illusory) person who "closely 'shadowed' changes in the patient's body position and posture".[16][17]
See also
- Aesthetic illusion – A type of mental absorption.
- Altered state of consciousness – Any condition which is significantly different from a normal waking state.
- Aporia – State of puzzlement or expression of doubt, in philosophy and rhetoric.
- Argument from illusion – argument for the existence of sense-data
- Augmented reality – View of the real world with computer-generated supplementary features.
- Cognitive dissonance – Stress from contradictory beliefs.
- Delusion – Psychological fixation of holding false beliefs in spite of clearly disqualifying proofs.
- Dream argument – Postulation about the act of dreaming
- Hallucination – A vivid perception in the absence of external stimulus that has qualities of real perceptions.
- Holography – Recording to reproduce a three-dimensional light field.
- List of cognitive biases – Systematic patterns of deviation from norm or rationality in judgment.
- Moon illusion – Perceived variation in the moon's size.
- Paradox – Statement that apparently contradicts itself.
- Pareidolia – Perception of meaningful patterns or images in random or vague stimuli.
- Simulated reality – Concept of a false version of reality.
- User illusion – Concept in the philosophy of mind.
References
- ISBN 0-205-30937-2
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- ^ a b c Kandel E.R., & Schwartz J.H., & Jessell T.M., & Siegelbaum S.A., & Hudspeth A.J., & Mack S(Eds.), (2014). Principles of Neural Science, Fifth Edition. McGraw Hill.
- Technology Reviewarticle)
- ^ "Robles-De-La-Torre & Hayward 2001" (PDF). Archived from the original (PDF) on 2006-10-03. Retrieved 2006-10-03.
- PMID 20076548.
- ^ "Robles-De-La-Torre & Hayward 2001" (PDF). Archived from the original (PDF) on 2006-10-03. Retrieved 2006-10-03.
- Technology Reviewarticle)
- ^ Zampini M & Spence C (2004) "The role of auditory cues in modulating the perceived crispness and staleness of potato chips". Journal of Sensory Studies 19, 347-363.
- ^ Barnett-Cowan M (2010) "An illusion you can sink your teeth into Haptic cues modulate the perceived freshness and crispness of pretzels" Archived 2015-06-13 at the Wayback Machine. Perception 39, 1684-1686.
- ^ Todrank, J & Bartoshuk, L.M., 1991
- ^ Herz R. S. & Von Clef J., 2001
- PMID 21787869.
- ISSN 1357-0978. Retrieved 2020-02-27.
- S2CID 4338465.
- S2CID 191491373
External links
- Universal Veiling Techniques Archived 2010-05-07 at the Wayback Machine
- What is an Illusion? by J.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.
- Silencing awareness of visual change by motion