5 Color Illusions and Why They Work

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National Geographic Channel

Think colors are objective facts? Think again! Color is more subjective than you might expect—it’s really all in your head. These illusions show you how.

1. Checkerboard Illusion

In this illusion, both block A and B are the same color.

Don’t believe it? Check this out.

It’s all because of color constancy, which helps the brain recognize objects regardless of the amount of light being reflected. Cone cells in our eyes help us see color. As these cones register different wavelengths of light, special neurons in the visual cortex try to make sense of the cone activity. Seeing that Square B is under a shadow, your brain assumes that the square must be even lighter than it really is.

2. Chubb Illusion

Another example of color constancy: the left inner box appears darker than the box on the right—although they’re the same color. Both squares reflect the same amount of light into your eyes, but they still appear different because of the context.

3. Scintillating Grid Illusion

This one is pretty trippy. Dark dots rapidly appear and disappear at the intersections. However, if you stare at one intersection, the crossroad remains white.

Scientists are still trying to put a finger on this one. One theory, called lateral inhibition theory, suggests that several photoreceptors in the eye send information to a retinal ganglion cell in the brain. As your brain interprets these signals, the most active brain cells inhibit and reduce the activity in neighboring cells, making them less excited. This creates an unequal black-white contrast.

4. The Cornsweet illusion

Lateral inhibition strikes again! Both panels are the same color. Just cover the fold with your finger to see it.

5. The Bezold Effect

Wilhelm von Bezold discovered that a color may appear darker depending on its context. In this picture, there’s only one shade of red, although the right side appears darker.

Scientists are still puzzled by this one. Some think lateral inhibition is to blame, although many disagree.

Learn more about how your brain perceives colors and all the other crazy, amazing things it can do. An all-new season of Brain Games starts Monday at 9/8c on the National Geographic Channel.

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January 10, 2014 - 7:00am
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