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. Seymour Simon writes and photographs nature from his hilltop home in Columbia County in upstate New York, where he lives with his wife Liz Nealon. Let your eyes explore this image freely and you will see a regular pattern of intersecting horizontal and vertical lines in the center, flanked by an irregular grid of misaligned crosses to the left and right. Choose one of the intersections in the center of the image and stare at it for 30 seconds or so. You will see that the grid "heals" itself, becoming perfectly regular all the way through. An isometric illusion (also called an ambiguous figure or inside/outside illusion) is a type of optical illusion, specifically one due to multistable perception. The Oppel-Kundt illusion is an optical illusion named after German physicists Johann Joseph Oppel [ de] (first mentioned this phenomenon in 1860) and August Kundt (first performed a systematic study of the illusion in 1863).

The Chubb illusion is an optical illusion or error in visual perception in which the apparent contrast of an object varies substantially to most viewers depending on its relative contrast to the field on which it is displayed. In Sander's parallelogram (1926) the diagonal line bisecting the larger, left-hand parallelogram appears to be considerably longer than the diagonal line bisecting the smaller, right-hand parallelogram, but is in fact the same length. The Pulfrich effect is the effect that covering one eye with transparent but darkened glass can cause purely lateral motion to appear to have a depth component even though in reality it doesn't; even a completely flat scene such as one shown on a television screen can appear to exhibit some three-dimensional motion, but this is an illusion due to the fact that darkening the scene for one eye causes the photoreceptors in that eye to respond more slowly.One way our visual system overcomes these limitations—to present us with the perception of a fully realized world, despite the fundamental truth that our retinas are low-resolution imaging devices—is by disregarding redundant features in objects and scenes. Our brains preferentially extract, emphasize, and process those unique components that are critical to identifying an object. Sharp discontinuities in the contours of an object, such as corners, are less redundant—and therefore more critical to vision—because they contain more information than straight edges or soft curves. The perceptual result is that corners are more sa­lient than non-corners. Seymour Simon is also a creator and the author of a series of 3D books and a series of Glow-in-the-Dark Books for Scholastic Book Clubs, a series of leveled SEEMORE READERS for Chronicle Books, and the EINSTEIN ANDERSON, SCIENCE DETECTIVE series of fiction books. His books encourage children to enjoy the world around them through learning and discovery, and by making science fun. He has introduced tens of millions of children to a staggering array of subjects; one prominent science education specialist described Simon's books as "extraordinary examples of expository prose." The Kanizsa triangle is an optical illusion first described by the Italian psychologist Gaetano Kanizsa in 1955. It is a triangle formed of illusory contours. Soon after placing the ad in American Way, Baccei says he was jolted awake in the middle of the night with an epiphany. “I realized I was selling the wrong thing. People wanted more autostereograms, and they’d buy it.” Baccei mortgaged his house, and with the help of Smith started Magic Eye as a sub-company under one of his existing businesses, N.E. Thing Enterprises. If you hold your gaze steadily on one of the "snake" centers, the motion will slow down or even stop. Our research, conducted in collaboration with Jorge Otero-Millan, revealed that the jerky eye motions—such as microsaccades, larger saccades, and even blinks—that people make when looking at an image are among the key elements that produce illusions such as Kitaoka's Rotating Snakes.

The Jastrow illusion is an optical illusion discovered by the American psychologist Joseph Jastrow in 1889. To Smith, the magic of Magic Eye goes well beyond the initial “ah-ha” moment. For some people, she adds, it’s almost like an addiction. “When you see it in 3-D, it puts you in an altered state,” she says. “It increases your alpha waves and makes you feel happy.”Like many optical illusions, different theories have been proposed to explain exactly why this happens. 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.