Do you see the Zöllner illusion like everyone else?
What part of the Zöllner illusion causes the effect?
Scientists are unsure why this (Zöllner) illusion works, but the short angled lines on top may fool your perception of depth and size constancy.
If a friend runs towards you, the image they project onto your retina becomes larger, but your brain interprets this as your friend getting closer to you, instead of them becoming a giant (or getting smaller if your friend runs away). This is size constancy.
Your brain also judges the size of things against the angles of a horizon or room corners, which is possibly what your brain is trying to do with the lines of this illusion.