Illusions show us ways that we do not see the world the way it is.
For example, the sizes of objects can change by simply moving where someone is in a scene.
By studying illusions we can learn important aspects about how our visual system works, such as
how we interpret depth and perceive size.
Sometimes depth is perceived even when no depth is apparent as in the Müller-Lyer Illusion
or depth is not perceived that is there as in the Ames Room.
And this alteration in the perception of depth can change the perceived size of object.
In addition, we do not just see objects but compare them to what is around.
Both the perceived brightness and perceived size of an object can be changed by what is around it.
So, let us end with a question. Is seeing believing?