Optical illusions are images that are visually misleading or deceptive. They occur when the information detected by the eyes is processed incorrectly by the brain. There are two main types - physiological illusions that occur naturally and cognitive illusions that are demonstrated by visual tricks. Some examples provided include the checker shadow illusion, Rubin vase illusion, Ponzo illusion, hollow-face illusion, and spinning circles illusion.

1. Optical Illusions

2. Optical Illusion- A Brief An optical illusion is always characterized by visually perceived images that, at least in commonsense terms, are deceptive or misleading. 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 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.

3. Checker Shadow Illusion The same color illusion — also known as Adelson’s checker shadow illusion, is an optical illusion published by Edward H. Adelson in 1995 . The squares A and B on the illusion are of the same color (or shade), although they seem to be different. "When interpreted as a 3D scene, our visual system immediately estimates a lighting vector and uses this to judge the property of the material."

4. As a further example, the two "A"s are both of the same color and do not change. The shadow is removed in two frames, and the colors of the chess board are reversed.

5. The Left-Right Conflict

6. Rubin Vase A classic Rubin vase. The faces can be seen in blue, and the vase in white. The same vase, but with the colors swapped . The illusion generally presents the viewer with a mental choice of two interpretations, each of which is valid. Often, the viewer sees only one of them, and only realizes the second, valid, interpretation after some time or prompting.

7. Ponzo Illusion The Ponzo illusion is an optical illusion that was first demonstrated by the Italian psychologist Mario Ponzo . He suggested that the human mind judges an object's size based on its background. He showed this by drawing two identical lines across a pair of converging lines, similar to railway tracks. The upper line looks longer because we interpret the converging sides according to linear perspective as parallel lines receding into the distance.

8. Isometric Illusion Are you looking at the outside or the inside of the two panels? An isometric illusion is a type of optical illusion , specifically one due to multistable perception . In the example figure at right, the shape can be perceived as either an inside or an outside corner. In general, any shape built entirely of same-length (i.e., isometric ) lines that does not clearly indicate relative direction between its components will evoke such a perceptual "flip-flopping".

9. This face of Björn Borg appears convex, (pushed out) but is actually concave (pushed in). Hollow-Face Illusion The Hollow-Face illusion is an optical illusion in which the perception of a concave mask of a face appears as a normal convex face.

10. Revolving circles The two circles seem to move when the viewer's head is moving forwards and backwards while looking at the black dot.

11. Box Illusion Floor tiles at the Basilica of St. John Lateran in Rome . The pattern creates an illusion of three-dimensional boxes.

12. Duck or Rabbit Horse or Frog Depending on whether you view this figure as facing right or left it can either be a duck or a rabbit. (Hint: the beak of duck is the rabbit’s ear ) Depending on whether you view this figure at what angle it can either be a frog or a horse (Hint: tilt the picture 90 o clockwise)

13. Ghost Spots Small grey spots appear at the intersections of the squares, but if you look directly at any one intersection, the grey spot disappears!

14. Read the Text in the Triangle This illusion presents a problem of familiarity; since the words "I love Paris in the springtime" are familiar to many people, they fail to notice that the word "the" appears twice.

15. Thank You

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