What does "illusion" refer to in the context of sensory perception?

In the context of sensory perception, "illusion" refers to misperceptions of actual sensory input. Illusions occur when the brain interprets sensory information in a way that does not accurately reflect the external reality. For example, a straight stick partially submerged in water may appear bent due to the refraction of light, leading to a sensory experience that differs from what is physically present.

This phenomenon highlights the complexities of how our cognitive processes can influence our perception of sensory data. Unlike hallucinations, which involve experiencing something that is not present at all, illusions involve a distortion of something that is actually there, leading to a different interpretation of the sensory experience. This distinction is important in understanding how the brain processes information and can sometimes lead to errors in perception.