A appears bigger. The Ponzo illusion is a geometrical-optical illusion that was first demonstrated by the Italian psychologist Mario Ponzo in 1911. He suggested that the human mind judges an object's size based on its background. He showed this by drawing two identical lines across a pair of converging lines, similar to railway tracks. A and B are the same.
Below is a variation of the Ponzo illusion:
The individual in back appears bigger, his head is close to the ceiling. But they are all the same size.
The Müller-Lyer illusion is an optical illusion devised by Franz Carl Müller-Lyer, a German sociologist, in 1889. The line segment with tails pointing outward is perceived to be longer than the line segment with the tails pointing inward. The lines are the same length.
The Hering illusion is a geometrical-optical illusions, discovered by German physiologist Ewald Hering in 1861. When two straight and parallel lines are in front of a radial background (like the spokes of a bicycle), the lines appear as if they are bowed outwards. They are perfectly straight.
Edward Adelson, a professor of vision science at MIT, created this illusion back in 1995 to demonstrate how our human visual system deals with shadows. When attempting to determine the color of a surface, our brains know that shadows are misleading and make surfaces look darker than they normally are. We compensate by interpreting shadowy surfaces as being lighter than they appear to the eye. So, we interpret square B, a light checkerboard tile that is cast in shadow, as being lighter than square A, a dark checkerboard tile. In reality, the shadow has rendered B just as dark as A.
On the checkerboard tile A seems much darker than tile B. Though seen in the revised image underneath, A and B are actually exactly the same color. In an image editing program, they will both register an RGB value of 120-120-120.
A variation of checker shadows shown here is a horizontal bar that seems to gradually move from light gray to dark gray in the opposite direction of the background. If you cover everything but the bar itself, you'll see that it's actually monochrome. Just one solid gray colored bar.
This "simultaneous contrast illusion" is similar to the checker shadow illusion. The brain interprets two ends of the bar as being under different lighting, and deduces what it thinks the bar's true shading would be. It thinks that the left end of the bar is a light gray object in dim lighting. The right end looks like a darker object that is well-lit.
See Vividly: https://www.seevividly.com/blog/5/6_Cool_Optical_Illusions_That_Tell_You_About_How_Your_Brain_Works
We can see here that our neurological perception of reality, our neuroreality as mentioned in Chapter 7, can actually be wrong. So we need to question our perceptions of reality, and scientifically analyze them, as these scientists did, to make sure our perception of reality is as close as possible to actual reality, ie: to make sure our perceptions are actually true. Recall, nature knows only truth.