The art (and science) of optical illusions

Visual trickery plays an important role in puzzles. It can be the clever rebus that challenges you to find the words each image represents, or a visual brain teaser that forces you to think outside the box.

But nowhere in the realm of puzzles is visual trickery more obvious or more disconcerting than in optical illusions. Some are simple, like the famous old woman/young woman image above (or this hilarious video version). But others are not only more complex, they’re absolutely mind-bending.

And if we’re talking mind-bending optical illusions, at some point, you have to mention the work of Akiyoshi Kitaoka.

[Akiyoshi Kitaoka’s “A Bulge,” featuring nothing but squares.]

Dr. Kitaoka is a professor of psychology at Ritsumeikan University in Kyoto, Japan, and he has extensively studied biology and psychology. He has quickly emerged as a modern master of optical illusions, utilizing not only shapes and color gradients to trick the eye, but also to simulate motion in a static image!

Two of the techniques frequently cited in his work with illusions are perceptual transparency and visual completion. Both rely heavily on how our brain and eye process the incredible amount of information we perceive every second of every day.

This is probably the most famous example of a visual completion illusion:

Basically, our brain employs mental shortcuts in order to simplify the information. For instance, visual completion (also known as filling-in) occurs when information unavailable to the eye is assumed to be there and mentally added by the brain.

Perceptual transparency, on the other hand, involves how we can perceive one surface behind another.

Check out this amazing photo from a published paper on perceptual transparency, entitled Zen Mountains:

[The mountains in the background look transparent,
even appearing to overlap each other in impossible ways.]

Dr. Kitaoka’s illusions utilize visual shortcuts and processes such like these, but his most famous creations involve a perceptual technique known as the Fraser-Wilcox Illusion, which involves using lighter and darker gradients of black and white in order to trick the eye into perceiving motion. Essentially, moving from dark to light gradually creates the illusion of motion.

Kitaoka’s work, however, maximizes this effect by employing contrasting color schemes in order to challenge the eye further.

Feast your eyes upon “Rotating Snakes,” Kitaoka’s most diabolical optical illusion:

[For the full effect, click the image and
scroll down for a full-screen version!]

By employing color as well, the rotation illusion is even more striking. In all honesty, I can’t look at it too long or my stomach starts to feel a little off-kilter!

Similarly, Kitaoka tricks the eye into perceiving waves rolling diagonally over this quilt-like sheet in “Primrose’s Field:”

As we understand more about the eye and how it perceives the visual stimuli it receives, as well as more about the brain and how it processes information, I suspect we’ll be able to craft even more convincing, mind-blowing, and unnerving examples of visual sleight of hand.

And undoubtedly, Akiyoshi Kitaoka will be leading the way.


Many thanks to Dr. Kitaoka for granting permission for me to feature three of his illusions in this post. You can check out more of his amazing work on his website, as well as some of his books on Amazon here!

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