Whoa. Thanks to these answers on Quora for the inspiration.
Surprise: They’re actually the same androgynous face, just with different levels of contrast, which makes one appear male and one female. Read more here.
The two images of the Leaning Tower of Pisa are identical, yet one has the impression that the tower on the right leans more, as if photographed from a different angle.
Read more here.
It’s not a parrot! It’s a woman covered in very meticulous body paint by artist Johannes Stoetter. See how he did it here.
The illusion derives from the lack of visual cues for depth. Read more here.
The purple dots disappear! 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.
The reason why we are perceiving one color as two different colors is because of the other colors surrounding the stripes.
Each eye has six to seven million cones, which are concentrated in a central yellow spot known as the macula. These cones measure color in different wavelengths, where some of which overlap. Our brain then compares by measuring the differences in wavelengths between the colors. When certain colors are combined, the brain can’t process the data from the cones correctly and we get confused.
Skeptical? Put your index finger over the line where the two boxes meet.
If you keep your eyes on the black dots, they appear to form and vanish at the intersections of the horizonal and vertical lines. The effect is diminished if one is very close to the screen, further away or if one views at a 45 degree angle. This illusion is known as the Scintillating grid.
In this illusion, it appears that there is one set of black figures and one set of white figures. In fact, the two sets of figures are exactly identical and the same color.
They appear different because the surrounding regions they are on cause the visual system to segment the images into layers. Thus one set appears to be white figures behind dark clouds, and the other set appears to be dark figures behind light clouds. If you cut out the figures, you’d see they’re identical.
The one on the left seems smaller. This is known as the Ebbinghaus Illusion.