Curved Red Objects Optical Illusion

Are these two objects the same size?

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Yes.

Explanation

There are two principals at work here. One is perspective and one is comparison to nearby objects. We live in a 3D world and try to project a 2D image into a 3D one. Using perspective, we assume the top object is farther away. It really is the same size, but we perceive it as bigger. Then we also compare its bottom curve to the curve of the lower object. That adds to the illusion of it being bigger.

Notice the two illustrations below. We have repeated the one from above. Then we have inverted it. In the inverted one, the same two principals apply, perspective and comparison to nearby objects. We still perceive the top one to be farther away which makes it seem bigger. But this time, when we compare the bottom curve of the top object, the optical illusion makes it look smaller. Even though these are conflicting perceptions, we still see the top one as a little larger than the bottom one.