What are illusions? How do they affect behavior?

Answer 1

Illusions are "errors" in perception as a result of unconscious expectations based off real stimuli. In other words, your brain fills in gaps on what "should" be there when there is information missing, or the brain becomes confused due to conflicting information. An illusion is different from a hallucination in that an illusion misinterprets real stimuli, where a hallucination responds to a stimuli that doesn't actually exist. Illusions can happen to any of the senses, but the most common are optical illusions, because sight tends to override the other senses.

Fortunately for us, our brain is able to accurately perceive stimuli most of the time, so illusions don't affect our behavior too often. However, when we are infants, we don't have a full range of depth perception due to restricted motion in our eyes and a lack of visual experience. Because of this visual distortion, infants are much more likely to walk off edges, fall down, trip over things, etc. Furthermore, people that get seizures and migraines will often experience auras, or optical disturbances based off light perception. This can alert them to act accordingly in order to maximize their safety.