What Causes the ‘Müller-Lyer Illusion’ and Why Does It Trick Us?

Imagine two arrows pointing in opposite directions. One has a line with arrows on the ends, and the other doesn’t. Even though they are the same length, one looks longer, that’s the Müller-Lyer illusion! It happens because our brain thinks the arrow points are part of the line. When the arrows point out, it makes the line look shorter, like it's pulled back by something. But when the arrows point in, it tricks your brain into thinking the line is longer.

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Examples

  1. A line with arrowheads pointing away looks shorter than a similar line without arrows.
  2. Your brain sees arrow points as part of the line, even though they're not connected.
  3. In a room, you might think one wall is farther away because of lines on it.

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