Now you see it: Best visual illusions of 2009 - New Scientist

Interactive Movie - COLOUR DOVE
"If you stare for a long time at a large coloured image and then glance at a white background, you'll see the same image appear, but in its complementary colours. That's because the receptors in the eye that pick up the image's colour have become tired and surrounding receptors that haven't been used take over. While this effect is well-known, Yuval Barkan and Hedva Spitzer from Tel-Aviv University recently demonstrated the first example of a related illusion that causes the background colour to linger in a different part of the image. In the Coloured Dove illusion (see below), a white dove appears on a coloured background. When the background is switched to white, the dove takes on a paler version of the original surrounding colour. The team hasn't yet figured out exactly why this happens. One theory is that the dove has actually taken on the background's complementary colour from the beginning, although we fail to perceive it until the background colour disappears."


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Interactive Movie -CURBALL - by Arthur Shapiro
"If you look directly at the "spinning" ball in this illusion by Arthur Shapiro, it appears to fall straight down. But if you look to one side, the ball appears to curve to one side. The ball appears to swerve because our peripheral vision system cannot process all of its features independently. Instead, our brains combine the downward motion of the ball and its leftward spin to create the impression of a curve. Line-of-sight (or foveal) vision, on the other hand, can extract all the information from the ball's movement, which is why the curve disappears when you view the ball dead-on."



CONTRAST COLOUR
"If you stare at this rotating circle, you should see three concentric circles: pink, blue and green. But when the circle stops moving, you can see that the arcs that create these circles are actually all black."


More visual illusions: newscientist.com