These two photographs of the Leaning Tower of Pisa are identical,
yet when your eyes and brain see two towers that are parallel,
they assume that they must be diverging as they rise into the air
These two photographs of the Leaning Tower of Pisa are identical, yet the tower on the right appears to lean more
than the tower on the left. Created by Frederick Kingdom and colleagues from McGill University in Montreal, the
illusion works because your eyes and brain treat the two photographs as if they're part of a single scene. If the
two towers really were next to one another and rising at the same angle, they'd appear to converge due to perspective.
So when your eyes and brain see two towers that are parallel, they assume that they must be diverging as they rise
into the air, and thus create the resulting illusion. Each year the Neural Correlate Society holds the Best Illusion
of the Year Contest to find new and wonderful illusions. The Leaning Tower illusion won the contest in 2007.
Explanation by RICHARD WISEMAN