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What You See In This Optical Illusion Says Plenty About Your Brain

Is it transparent glass or reflective metal?
What do you see?
What do you see?

What do you see when you look at this optical illusion?

Do you see a transparent glass object or a reflective metal one? Now try this next image:

Similar or different? UNSW School of Optometry and Vision Science researcher Juno Kim said the two images were the identical, just flipped upside down, and that caused most people's brains to see things differently.

He said that while people perceived the first object to be transparent like glass, when they viewed it in the second orientation, they thought it was reflective like metal or a kooky mirror.

"It's a brand new optical illusion," Kim said.

"It shows that our brain is asking: which way is up?"Juno Kim

"It demonstrates the visual system has learnt to rely on the orientation of the horizon, and whether bright highlights are at the top or the bottom of an object, to work out whether objects are transparent or opaque.

"It shows that our brain is asking: which way is up?"

Kim said our brains mostly searched for the horizon.

"Our brain is sophisticated, but when it is trying to infer the material composition of an object just from the distorted pattern of light reflected from the surface, it makes guesses based on previous experience," Kim said.

"This optical illusion appears to be driven by two main biases in the brain. The first is the assumption that a light source usually comes from above. This bias is the reason people look scary and very different when they put a torch under their chin. The brain is used to processing faces with the light coming from above.

"And the second bias is that most objects tend to be convex, or round overall."

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