What term refers to a misperception or misinterpretation of an actual external stimulus?

The term that refers to a misperception or misinterpretation of an actual external stimulus is an illusion. An illusion occurs when a sensory stimulus is misperceived due to a distortion of reality, but the external stimulus is present and real. For instance, a person might see a stick in the water and perceive it as being bent, even though it is straight; the misinterpretation is of an actual object.

In contrast, hallucinations involve perceiving something that is not there at all, such as hearing voices or seeing things that do not exist. Anergy refers to a lack of energy or response, often in the context of the immune system, rather than a perceptual experience. Delusions are fixed false beliefs that are resistant to reason or confrontation with actual facts, and while they relate to misinterpretation, they do not pertain to sensory perceptions of real external stimuli. Therefore, the correct identification of an illusion captures the essence of this type of perceptual discrepancy.