Last reviewed 01/2018

An illusion is a perceptual error or misinterpretation.

Examples of illusions include a person looking at a building outside their window interpreting it as the hull of a large ship that is about to sail, thinking a tree in the dark is a man, or thinking a voice in a crowd is talking to them.

Illusions are more common when there is a reduced level of consciousness, for example in delirium.