Optical Illusions

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A vanishing puzzle is a mechanical optical illusion showing different numbers of a certain object when parts of the puzzle are moved around. [4] The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. The Orbison illusion is an optical illusion that was first described by the psychologist William Orbison in 1939. Alex Fraser and Kimerly J. Wilcox discovered this type of illusory motion effect in 1979, when they developed an image showing repetitive spiral arrangements of luminance gradients that appeared to move. Fraser and Wilcox's illusion was not nearly as effective as Kitaoka's il­lusion, but it did spawn a number of related effects that eventually led to the Rotating Snakes. This family of perceptual phenomena is characterized by the periodic placement of colored or grayscale patches of particular brightnesses.

Qian L, Liu S, Lei Q. Illusory distance modulates perceived size of afterimage despite the disappearance of depth cues. PLOS ONE. 2016;11(7):e0159228. doi:10.1371/journal.pone.0159228 Your brain creates a simulation of the world that may or may not match the real thing. The "reality" you experience is the result of your exclusive interaction with that simulation. We de­fine "illusions" as the phenomena in which your perception differs from physical reality in a way that is readily evident. You may see something that is not there, or fail to see something that is there, or see something in a way that does not reflect its physical properties.

Two Faces

A Hybrid image is an optical illusion developed at MIT in which an image can be interpreted in one of two different ways depending on viewing distance. Troxler's fading: When one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point will fade away and disappear.

Also known as "poiuyt" or "devil's fork", this illusion is an impossible image because in reality the shape cannot exist. Just as a painter creates the illusion of depth on a flat canvas, our brain creates the illusion of depth based on information arriving from our essentially two-dimensional retinas. Illusions show us that depth, color, brightness, and shape are not absolute terms but are subjective, relative experiences created actively by our brain's circuits. This is true not only of visual experiences but of any and all sensory perceptions, and even of how we ponder our emotions, thoughts, and memories. Whether we are experiencing the feeling of "redness," the appearance of "square­ness," or emotions such as love and hate, these are the result of the activity of neurons in our brain.The fad caught fire, and Magic Eye had a head start. For more than a year, he and Smith worked fifteen-hour days, seven days a week, cranking out images for licensees like Disney, Looney Tunes, and even eye doctors, who wanted to latch on to the trend. There was a sense of urgency, if only because Baccei believed this was a once-in-a-lifetime opportunity. “Tom and I both knew this wasn’t going to last forever,” Gregorek said. The Penrose stairs was created by Lionel Penrose and his son Roger Penrose. [3] A variation on the Penrose triangle, it is a two-dimensional depiction of a staircase in which the stairs make four 90-degree turns as they ascend or descend yet form a continuous loop, so that a person could climb them forever and never get any higher. The Vertical-horizontal illusion is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line of the same length.