A moving square appears to change in color, though the color is constant. pic.twitter.com/phzLNgfIZy
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) August 14, 2018
Take a look at the video above and you’ll probably see a square traveling left to right on the gradient, changing color as it goes. But what if you discovered the moving square actually stays the same color the whole time? That’s right, once again our eyes are deceiving us with another optical illusion.
This video is just one example of a lightness illusion, which was posted by experimental psychologist Akiyoshi Kitaoka, who studies visual perception. A professor at Kyoto’s Ritsumeikan University, Kitaoka’s faculty page is filled with incredible optical illusions. He also often uses Twitter to send intriguing illusions out into the world, forcing us to examine why our eyes may be deceiving us.
There are many types of lightness illusions, including the Checker Shadow Illusion, but how do they work? It’s all about perception. First, we must understand that when our eyes look at something, light levels vary and they must take in a lot of information. This includes reflectance (how much light bounces off a surface), lightness (how our eyes perceive the reflectance), brightness (the perceived intensity of the light), and luminance (how intense the light is based on the sensitivity of our visual system).
When we are trying to pick out an individual object, while processing all this information, our brain may discount some of the factors in order to allow our eyes to perceive the object. “A gray surface in sunlight may have much higher luminance than it has in the shade, but it still looks gray. To achieve the task of ‘lightness constancy,’ the visual system must discount the illumination and other viewing conditions and estimate the reflectance.” writes Professor Adelson, the man who first published the Checker Shadow Illusion.
In these cases, our brain does its best based on past experience in 3D environments, which often results in errors when looking at 2D designs. As the authors of a 2007 study astutely note, “Sometimes the best way to understand how the visual brain works is to understand why it sometimes does not,” thus explaining why optical illusions have long fascinated scientists.
This demonstration shows how lightness illusions cause your brain to perceive different colors.
ん～、まあまあかな。 pic.twitter.com/fRtRlS5ozv
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) August 18, 2018
Enjoy more lightness illusions shared by Akiyoshi Kitaoka.
There appear to be bluish spirals and greenish ones, though they are the same color. pic.twitter.com/b1oeioojhc
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) August 21, 2018
There appear to be squares of different colors, though they are the same color gradation. pic.twitter.com/941ES969cQ
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) August 20, 2018
The hair and clothes in the left image appear to be whitish whereas those in the right one appear to be blackish, though they are the same stripes of white and black. pic.twitter.com/fquLs3rQX8
— Akiyoshi Kitaoka (@AkiyoshiKitaoka) August 18, 2018
h/t: [IFLScience!]
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