Question 19
There do not seem to be any parallel lines here. Or, are there?
What causes these illusions?
Optical illusions make our eyes and brain see things differently from how they truly are.
Step 1 — The central star illusion
Look at the top image. It has many lines. Some lines go straight up and down. These vertical lines are perfectly straight. They are also parallel to each other. The other lines spread out from the center. They look like spokes on a wheel. These spokes cross the vertical lines. This crossing confuses our brain. Our eyes think the vertical lines bend. But they are actually straight. This is an optical illusion. The central point draws our attention.
Step 2 — The zigzag pattern illusion
Now look at the bottom-left image. It has a pattern of black shapes. These shapes are slanted. They look like zigzags. The white spaces are important. Look at the white horizontal lines. These white lines are perfectly straight. They are also parallel to each other. The bold black shapes trick our eyes. They make the white lines look tilted. Our brain sees the slanted black. It makes us think the white lines slant too. This is another optical illusion.
Step 3 — The radiating lines illusion
Finally, look at the bottom-right image. It has two long horizontal lines. One is at the top. One is at the bottom. These two lines are perfectly straight. They are also parallel to each other. Many diagonal lines spread out. They come from a central point. These lines look like wheel spokes. They create a strong visual effect. This effect makes the horizontal lines curve. They seem to bend inward. Our brain interprets this as depth. But the lines are truly straight. This is a classic optical illusion.
Answer
(a) In the top image, the vertical lines are actually parallel. The radiating lines crossing them create an optical illusion, making the vertical lines appear bent or not parallel. (b) In the bottom-left image, the horizontal white lines are actually parallel. The bold, slanted black shapes around them create an optical illusion, making the white lines appear tilted or zigzagging. (c) In the bottom-right image, the two long horizontal lines are actually parallel. The many diagonal lines radiating from the center create an optical illusion, making the horizontal lines appear to curve inward.
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There do not seem to be any parallel lines here. Or, are there?
What causes these illusions?