It’s Just An Illusion
This is not just any illusion, this is the Muller-Lyer Illusion designed by a German sociologist of the same name in 1889. It is actually an optical illusion containing three arrows. The illusion operates under the hypothesis of size constancy mechanism, using angles of concave and convex perspectives.
If you look at the above image, Wall A’s length looks narrower than Wall B’s. However, upon closer investigation, we can see that they are actually the same length. Our minds are duped by the angle perspectives, but if you take a ruler to your screen, you will see that Wall A and Wall B are identical in length. Crazy, hey?