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    What is Illusion?

    Published: October 08, 2018

    Illusion, a misrepresentation of a “real” sensory stimulus that is, an interpretation that contradicts objective “reality” as defined by the general agreement. For example, a child who perceives tree branches at night as if they are goblins may be said to be having an illusion. An illusion is distinguished from a hallucination, an experience that seems to originate without an external source of stimulation. Neither experience is necessarily a sign of psychiatric disturbance, and both are regularly and consistently reported by virtually everyone.

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    What is Illusion?

    • 1. Slide1 ILLUSION What is Illusion? Best Illusions
    • 2. Slide7 WHAT IS ILLUSION? Illusion, a misrepresentation of a “real” sensory stimulus that is, an interpretation that contradicts objective “reality” as defined by the general agreement. For example, a child who perceives tree branches at night as if they are goblins may be said to be having an illusion. An illusion is distinguished from a hallucination, an experience that seems to originate without an external source of stimulation. Neither experience is necessarily a sign of psychiatric disturbance, and both are regularly and consistently reported by virtually everyone.
    • 3. Slide2 TYPE OF ILLUSION 01 Auditory Phenomena 4 Visual Illusions 2 Optical Phenomena 3 Percevier Illusions 5 Sensory Illusions
    • 4. Slide22 A common phenomenon is the auditory impression that a blowing automobile horn changes its pitch as it passes an observer on a highway. This is known as the Doppler effect, for Christian Doppler, an Austrian physicist, who in 1842 noted that the pitch of a bell or whistle on a passing railroad train is heard to drop when the train and the perceiver are moving away from each other and to grow higher when they are approaching each other. The sound heard is also affected by factors such as a wind blowing toward or away from the person 1 Optical Phenomena
    • 5. Slide20 Numerous optical illusions are produced by the refraction (bending) of light as it passes through one substance to another in which the speed of light is significantly different. A ray of light passing from one transparent medium (air) to another (water) is bent as it emerges. Thus, the pencil standing in water seems broken at the surface where the air and water meet; in the same way, a partially submerged log in the water of a swamp gives the illusion of being bent. 2 Optical Phenomena
    • 6. Slide21 Rainbows also result from refraction. As the sun’s rays pass through rain, the droplets separate (refract) the white light into its component colours. As rays of white light from any source pass through a prism, they are refracted to give the appearance of a spectrum of colour, as in the rainbow of a summer morning. Under certain conditions, elaborate mirages that look like cities, forests, or “unidentified flying objects” may appear on the horizon, or ships in a nearby body of water may appear to be plying the sky of a desert. 2 Optical Phenomena
    • 7. Slide23 Some illusions are related to characteristics of the perceiver, namely the functioning of the brain and the senses, rather than to physical phenomena that distort a stimulus. Many common visual illusions are perceptual: they result from the brain’s processing of ambiguous or unusual visual information. Other illusions result from the aftereffects of sensory stimulation or from conflicting sensory information. Still others are associated with psychiatric causes. 3 Percevier Illusions
    • 8. Slide24 When an observer is confronted with a visual assortment of dots, the brain may group the dots that “belong together.” These groupings are made on the basis of such things as observed similarity (e.g., red versus black dots), proximity, common direction of movement, perceptual set (the way one is expecting to see things grouped), and extrapolation (one’s estimate of what will happen based on an extension of what is now happening). 4 Visual Illusions
    • 9. Slide25 Many sensory illusions may be described as the aftereffects of the stimulation, or overstimulation, of the senses. Sensitivity in any of the senses may be measured as the just-perceptible intensity (threshold, or limen) of the appropriate stimulus. The smallest detectable stimulus is called the absolute threshold, while the smallest detectable change in the intensity of a stimulus is called the difference threshold. Such thresholds can serve as points of reference, or anchors, against which subsequent stimuli are judged or perceived. Yet sensory anchors fluctuate within the same individual under different conditions, and in some cases they can mislead a person about the properties of subsequent stimuli. For example, two successive stimuli may be identical but nevertheless give the illusion of being different 5 Sensory Illusions
    • 10. Slide9 HISTORY OF ILLUSION
    • 11. Slide30 HISTORY OF ILLUSION The illusion is based on the fact that at any given developmental stage, an individual can observe a relatively low level of maturity in previous stages. The phenomenon affects teenagers, middle-aged individuals, and seniors. In general, people tend to see significant changes in hindsight, but fail to predict that these changes will continue. For example, a 20-year-old's impression of how great a change they will undergo in the next ten years will not be as extreme as a 30-year-old's recollection of the changes they underwent between the ages of 20 and 30. The same phenomenon is true for people of any age. The reason for the illusion has not been studied, although researchers speculate that a resistance or fear of change may be causal.
    • 12. Slide8 BEST OPTICAL ILLUSIONS
    • 13. Slide29 BEST OPTICAL ILLUSIONS
    • 14. Slide26 Young woman vs. old woman
    • 15. Slide27 Penrose Stairs
    • 16. Slide28 The Rabbit Duck Head
    • 17. Slide18 SOURCES https://www.mnn.com/ www.psychologytoday.com https://www.wikizero.pro/index.php?q=aHR0cHM6Ly9lbi53aWtpcGVka WEub3JnL3dpa2kvRW5kLW9mLWhpc3RvcnlfaWxsdXNpb24