December 19, 2017

See Zig-Zag Lines in This Optical Illusion? Then You Have ‘Curvature Blindness’!

Take a look at those lines in the image below. What kind of lines do you see? Are they sharp edgy zigzags, or curvy waves? Or do you see both? If yes, then join the club! you have curvature blindness too! (Don’t worry, it’s not an actual medical condition.)


Dr Kohske Takahashi, a psychologist at Chukyo University in Japan, recently discovered this optical illusion called as ‘curvature blindness illusion’ giving an example that your eyes can fool you sometimes and you can not count on them always when looking at something.

In the picture, you probably might have seen both zigzag lines and wavy lines in alternate pairs – well you will at least if you’re staring at the lines present in the middle part of the picture with the grey background. Now, clearly observe the lines in the top-left and bottom-right areas of the image i.e, the lines present in the white and black backdrop. Find anything different?

Yes, all the lines curvy. There are no sharp points at all. It’s just a quirk of the brain which is adding in the peaks. But why do the majority of the people see zigzag lines in the picture, when in reality every line in the image is wavy?

Takahashi explained this behaviour in journal i-perception saying that the humans may have evolved to spot corners ahead of curves, and when there is confusion.


“We propose that the underlying mechanisms for the gentle curve perception and those of obtuse corner perception are competing with each other in an imbalanced way and the precepts of a corner might be dominant in the visual system,” Takahashi explained in his paper.

“I’d say that our eyes and brain may have been evolutionarily adapted to detect corners more efficiently than curves,” Takahashi told The Telegraph.

“We are surrounded by artificial products, which have much more corners than natural environment does, and hence our visual. This visual phenomenon doesn’t cause the problem in our everyday life, otherwise, someone should have found this illusion earlier.”

Another factor that adds when perceiving the illusion is that in the picture, the zigzags with light and dark grey lines running from peak to the valley of each curve accentuates the illusion that those sections of the wave are slanted straight lines just like the sharp edges of steep mountains.

Do you have curvature blindness too? Share your thoughts in the comments below!

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