This award-winning optical illusion will make your brain hurt - here's how it works

• The Best Illusion of the Year contest named its 2020 winner: "3D Schröder Staircase" by Kokichi Sugihara.
• The staircase has two interpretations, both of which look like a staircase being viewed from above.
• The staircase's incline is an illusion — the two "legs" of the staircase are actually the same length.

The Best Illusion of the Year Contest chose a mind-boggling winner in its 2020 competition.

Schröder staircases are usually two-dimensional illusions that play with perspective reversal. "3D Schröder Staircase," created by Japanese mathematician Kokichi Sugihara, puts a new spin on the classic illusion with a three-dimensional model.

From two different viewpoints, Sugihara's model appears to be a staircase viewed from above. Here's a video of the illusion in action:

Sugihara places a red cone at the "top" of the steps and rotates them 180 degrees, which puts the cone at the "bottom" of the steps. In both cases, the staircase appears to be at an incline. But the incline is an illusion.

When Sugihara rotates the model, he reveals that the two "legs" of the staircase are actually the same length, and the stairs are all on the same level.

"This object is an example of my experimental material to investigate the behavior of the brains, which are apt to misperceive 2D pictures as 3D objects when they are embedded in real 3D structures," Sugihara wrote on his website. "The Schroeder Staircase, which is known as an ambiguous picture for more than 150 years, is decorated by real 3D side walls and support columns. As the result, we perceive new ambiguity, which is different from that of the original Schroeder Staircase."

The Best Illusion of the Year Contest, which is a "celebration of the ingenuity and creativity of the world's premier illusion research community," announced its 2020 winners in December. Other finalists' videos can be viewed on the contest's website.

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