While new optical illusions go viral all the time, here are some of the most famous illusions that have kept us scratching our heads for years.

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PERHAPS it is difficult to demonstrate primary constancy scaling independently of the distortion illusions, but its effects are not limited to plane figures. For example, the apparent size of the Moon ...

Geometric patterns have been used in art for centuries. They can be seen in the world’s greatest artworks, from Francisco José de Goya to Andy Warhol. “Geometric drawing is fun and rewarding,” says ...