1. Stare at the red dot on the girl’s nose for 30 seconds.
2. Turn your eyes to a plain surface (your ceiling or blank wall).
3. Blink repeatedly and quickly.
4. Mind = Blown!
Here’s an explanation of how color vision works that pretty much explains this trick:
Human color vision relies on special cells in the retina of the eye called cones. There are three types of cones. “Red” cones are sensitive to red light, “green” cones are sensitive to green light, and “blue” cones are sensitive to blue light.
When we look at a beam of light that stimulates only the red cones, but not the green or blue cones, we see pure red. Light that stimulates only the green cones, but not the red or blue cones, is pure green. Light that stimulates only the blue cones, but not the green or red cones, is pure blue.
But can see many more colors than just red, green, and blue. How can we see other colors? All the other colors that we see result from the stimulation of combinations of red, green, and blue cones. For example, if we look at a beam of light that stimulates both the red and green cones equally, but not the blue cones, we see yellow. Light that stimulates the blue and green cones equally, but not the red cones, results in a blue-green color called cyan. Light that stimulates the blue and red cones equally, but not the green cones, results in a bluish-red color called magenta. Light that stimulates all three types of cones equally is white or gray. All of the thousands of colors that we can see are the simply the result of weaker or stronger stimulation of the red, green, and blue cones.
These three colors red, green, and blue are called the primary colors for human color vision. (Primary colors are any set of colors from which all other colors may be derived).