20 Astonishing Visual Tricks

Optical illusions are visual phenomena where the images perceived by the eye deceive the brain, creating a perception that contradicts the actual physical reality. These fascinating tricks occur when the brain interprets visual information in a way that doesn't align with the true nature of the stimulus. Below is a curated list of twenty mind-bending illusions.

20. Blivet

A blivet, often referred to as a poiuyt, is a perplexing optical illusion and an impossible object. It features three cylindrical prongs at one end that seemingly morph into two rectangular prongs at the opposite end, creating a visually baffling effect.

19. Bezold Effect

Named after Wilhelm von Bezold, a German meteorology professor (1837-1907), the Bezold Effect is a visual phenomenon where a color's appearance changes based on surrounding hues. In the example above, the red shade appears brighter against white and darker against black.

18. Café Wall Illusion

The café wall illusion, initially identified by Dr. Richard Gregory, is a visual phenomenon where straight horizontal lines seem to curve. Gregory noticed this intriguing effect on the tiled walls of a café located at the base of St Michael’s Hill in Bristol. The illusion is created using alternating light and dark 'bricks' arranged in staggered rows, with each 'brick' framed by a 'mortar' layer (shown in grey). The mortar must be a shade intermediate between the light and dark bricks for the illusion to work effectively.

17. The Chubb Illusion

The Chubb illusion is a visual effect where the perceived contrast of an object changes significantly based on its surrounding context. When a low-contrast texture is placed against a uniform background, it appears to have greater contrast compared to when it is surrounded by a high-contrast texture. This phenomenon was first documented by Chubb and his team in 1989.

16. Ebbinghaus Illusion

The Ebbinghaus illusion is a visual phenomenon that plays with our perception of size. In its most famous form, two equally sized circles are placed close together. One is encircled by larger circles, while the other is surrounded by smaller ones. This setup makes the first central circle seem smaller than the second, despite both being identical in size.

15. Fraser Spiral Illusion

This illusion, often referred to as the false spiral or twisted cord illusion, creates the deceptive appearance of a spiral through overlapping black arc segments. In reality, these arcs form a series of concentric circles, not a spiral.

14. Hermann Grid Illusion

The Hermann grid illusion, discovered by Ludimar Hermann in 1870 while reading John Tyndall’s work on sound, is marked by the perception of faint grey spots at the intersections of a white grid against a black background. These spots vanish when one focuses directly on the intersection.

13. Hering Illusion

The Hering illusion, identified by German physiologist Ewald Hering in 1861, features two straight vertical lines that appear to curve outward. This effect is caused by the background's lined pattern, which mimics a perspective design and creates a misleading sense of depth.

12. Impossible Cube Illusion

The impossible cube, or irrational cube, is an optical illusion based on the ambiguity of a Necker cube. It is typically depicted as a Necker cube with edges resembling solid beams, enhancing its visual paradox. This design exploits the human tendency to interpret two-dimensional images as three-dimensional objects, making it more perplexing than a standard Necker cube.

11. Isometric Illusion

An isometric illusion, also known as an ambiguous figure or inside/outside illusion, is a type of optical illusion resulting from multistable perception. In the image above, the shape can be interpreted as either an inside corner or an outside corner, depending on the viewer's perspective.

10. Jastrow Illusion

The Jastrow illusion, identified by American psychologist Joseph Jastrow in 1889, presents two identical figures where the lower one appears larger due to the arrangement of their shapes.

9. Kanizsa Triangle

The Kanizsa triangle, introduced by Italian psychologist Gaetano Kanizsa in 1955, is an optical illusion where a white equilateral triangle seems to appear, even though no such triangle is actually drawn in the image.

8. Lilac Chaser

The Lilac Chaser, also referred to as the Pac-Man illusion, is a visual phenomenon featuring 12 blurred lilac (or pink/magenta) disks arranged in a circular pattern, similar to clock numbers, around a small black cross on a grey background. When one disk vanishes briefly (around 0.1 seconds), followed by the next (after about 0.125 seconds), and so on clockwise, staring at the cross for roughly 20 seconds creates the illusion of a gap moving around the circle. Eventually, a green disk appears to replace the lilac disks, making them seem to disappear or be erased.

7. Motion Illusion

A motion illusion is a type of optical illusion where a stationary image appears to move due to the interplay of color contrasts and the positioning of shapes. To fully experience this effect, click on the image above to view it in its full size.

6. Necker Cube

The Necker cube is a classic example of an ambiguous line drawing, depicting a wire-frame cube in isometric perspective. In this representation, parallel edges of the cube are shown as parallel lines, and where lines intersect, it is unclear which line is in front or behind. This ambiguity allows the image to be interpreted in two distinct ways, often causing it to flip between these interpretations when stared at for a period of time, a phenomenon known as multistable perception.

5. Orbison Illusion

The Orbison illusion, first identified by psychologist William Orbison in 1939, creates a visual distortion where both the bounding rectangle and inner square appear warped due to the presence of radiating lines. The background suggests a perspective, tricking the brain into perceiving the shapes as distorted. This illusion is a variation of the Hering and Wundt illusions.

4. Poggendorff Illusion

The Poggendorff Illusion, named after German physicist Johann Poggendorff (1796-1877), who first described it in 1860, involves the brain misinterpreting the alignment of diagonal lines intersecting horizontal and vertical edges. In the image, a straight black and red line is interrupted by a grey rectangle, causing the blue line to appear as a continuation of the black line, despite the second image clearly showing this is not the case.

3. Zöllner Illusion

In this illusion, the black lines appear to be non-parallel, even though they are actually parallel. The shorter lines intersect the longer ones at an angle, creating the illusion that one end of the longer lines is closer to the viewer than the other. This effect, reminiscent of the Wundt illusion, may be attributed to the perception of depth created by the angled lines.

2. White Illusion

White’s illusion demonstrates how identical luminance levels can produce varying perceptions of brightness depending on the surrounding context. Despite the gray rectangles having the same luminance, those placed against dark stripes appear brighter than those against light stripes. This effect contradicts the expectations of simultaneous contrast, where rectangles adjacent to dark stripes would typically appear darker.

1. Adelson’s Checker Shadow Illusion

The illusion depicts a checkerboard with black and white squares and a green cylinder casting a shadow across it. Interestingly, the 'white' squares within the shadow (labeled 'B') and the 'black' squares outside the shadow (labeled 'A') are the same shade of gray. Despite their identical color, squares A and B appear strikingly different due to the surrounding context and shadow.