Blivet
Also called poiuyt, a blivet is an unreadable or an impossible object. The image, at first glance, seems to be a three cylindrical forked object on one end that somehow inexplicably change into a two rectangular forked one on the other.
Bezold Effect
This illusion is named after the German meteorologist Wilhelm von Bezold, who learned that a color of similar shade may appear darker or lighter depending on neighboring colors. In the example above, the red appears to be of a darker shade when placed with the black while it appears lighter with the white.
Necker Cube
First published by Swiss crystallographer Louis Albert Necker, this illusion consists of line drawing of a cube's frame wherein the intersecting lines seem to make the image rather confusing, rendering it interpretable in two valid solutions. So when one focuses at the image, it will repeatedly seem to fluctuate backward and forward, thereby, puzzling its reader as to which is the front and which is behind.
Jastrow Illusion
Created in 1889 by Joseph Jastrow, an American psychologist, this illusion, as demonstrated, is composed of two figures of the same size, however the lower one appears to be bigger.
Impossible Cube Illusion
This illusion draws on the ambiguity inherent in the Necker cube, but instead of lines, solid beams are drawn, giving the figure even greater ambiguity as to their interpretation. The illusion plays tricks on one's visual perception of two dimensional images as three dimensional objects.
The Chubb Illusion
This is an illusion wherein the apparent contrast of an object varies considerably, depending on the texture of the background. Low-contrast images, when placed on a plain background, appear to have a higher contrast than when placed on a high-contrast background.
Café Wall Illusion
First observed by Dr. Richard Gregory and Priscilla Heard in the pattern of tiles on the café walls in England, this illusion has the strange effect that makes parallel straight lines appear seemingly crooked. To create such effect, dark and light “tiles” are arranged alternately in staggered rows, with each row and each brick bordered by a color shade that is between the shades of the “tiles” used.
Ebbinghaus Illusion
An illusion involving relative size perception, the most common example is that of two circles of identical size, which are placed side by side, with one is encircled by large circles while the other by small circles. The former middle circle would then look smaller than the latter middle circle.
Zöllner Illusion
Named after the German astrophysicist Johann Karl Friedrich Zöllner, the black parallel lines of this illusion look as if they are not parallel at all. Since the short lines are drawn at an angle to the long lines, it gives the impression of depth, misleading one to perceive that one end of the long lines to be closer to us than the other.
Fraser Spiral Illusion
First described in 1908 by the British psychologist James Fraser. This illusion appears to be spiral due to the coinciding black arc sections, which, in actuality, are a succession of concentric circles. The distortion results from using a arrangement of regular lined circular patterns with contrasting colored strands. The principle applied here is quite similar to the Zöllner's and the café wall illusion, wherein a series of slanted elements deceives the eyes into perceiving non-existent variations.
