1. Fraser's Spiral
Otherwise known as the 'false optical illusion' this image is made from several overlapping circles that appear to be in spiraling motion. However, the image is actually made up of normal circles. It's what is going on inside the circles that causes you to perceive eternal motion.
2. Ebbinghaus's Illusion
It's amazing how we assess the size of something relative to what surrounds it. This illustration from German psychologist Hermann Ebbinghaus demonstrates this effect simply and clearly. Have a look at the orange circles and consider how big they appear relative to one another. They are actually the same size, yet because one is surrounded by large circles it appears small, whereas the one surrounded by small circles appears big.
3. An Illogical Cube Illusion
Charles Cochran conceived this impossible cube in 1996, yet I am still unsure how. Can you work out how the corners of this cube actually come together? As a 2D image it makes sense, but when your brain imagines it as a 3D cube, the haywire begins.
4. Zollner's Illusion
Another image that creates the illusion of depth was accidentally noticed on a piece of cloth by Johann Zollner, a German astrophysicist, in 1860. Because some short lines go from top to bottom, they appear to be standing up at an angle, whereas the short lines that go left to right appear to be lying down on an imaginary surface.
5. Jastrow's Illusion
Is there anyone who doesn't feel that these shapes are of a different size? In fact, Joseph Jarrow's A and B illusion shows two identical images placed in a certain position. For some reason, our minds cannot visualize that they are the same.
6. Kanizsa's Triangle
Italian psychologist Gaetano Kanizsa's image here is meant to demonstrate that people often imagine things that are, in fact, not really there. By simply putting together the above lines and broken disks, most people inevitably 'see' a white triangle, which has no outline or reality at all.
7. Poggendorff's Illusion
When showed the picture on the left, people instinctively believe that the black line is a continuation of the blue line. But, as the second image on the right shows, it is actually a continuation of the red line. As yet, no convincing explanation of why we make this mistake has been made.
8. The Blivet
Otherwise known as the 'impossible trident', this illusion has perplexed many brains for decades. Can you figure out this illusion? I have tried and come up with nothing so far.
9. White's Illusion
Our mind is not only fooled by the relativity of various sizes but also colors. Have a look at the gray rectangles. Those placed on the white lines appear darker than those on the black lines. However, they are the same tone of gray. It's all about juxtaposition.
10. A Motion Illusion
This seemingly simple image is actually so sophisticated that it makes us feel as though it's floating and palpitating. Take a look at the white and blue shadows placed on the blue dots and try to figure out what is going on inside your mind.
11. The Hermann Grid Illusion
This classic was first spotted by Ludimar Hermann in 1870 while reading a book. Our peripheral vision picks up little grey dots at the intersections between the black squares. Yet, whenever you look at them directly, they vanish - because they don't exist!
12. Dali's Elderly Lovers and Some Singers
Salvador Dali loved to mess with his audience's visual perceptions, but this image is particularly striking. Whenever I look at it, I feel that I can't pin down which of two scenes I am staring at. Whenever I try to see just the musicians I start to notice the old lovers. I could look at it for hours.
13. An Illusory Rotation Effect
To make this deceptively plain image come to life simply stare at the black dot in the middle for a few moments. Then begin to slowly nod your head back and forth. Do you see the circles rotating?
14. The 'Wall Cafe'
The ten lines in this image of checkered squares appear to be bent, but they are actually totally parallel to each other. This weird sensation was first noticed by Richard Gregory while seated in a cafe in the English city, Bristol.
15. Multiple Rotating Wheels
This may be the greatest of the 15 here. 16 wheels each seem to be moving in various contrary directions. That is until you look directly at one, then it stops. Can you make the whole image stop moving? Give it a try.