Which of the following is NOT one of the visual illusions listed?

Motion blur is not classified as one of the common visual illusions encountered in aeromedical practice. The other options, such as relative motion, false horizon, and crater illusion, are recognized visual illusions that can significantly impact pilot performance and judgment.

Relative motion refers to the perception of movement of objects in relation to one's own movement and can affect depth perception, especially in certain flying conditions. The false horizon illusion occurs when the horizon is obscured or misleading, leading pilots to misinterpret the aircraft's orientation. The crater illusion involves the misperception of elevation during approach to landing, which can result in dangerous underruns or overflights.

Since motion blur is more associated with the effects of speed and visual acuity rather than a specific visual illusion that misleads orientation or depth perception, it does not fit into the context of the other options listed. Thus, identifying motion blur as not being one of the recognized visual illusions showcases a solid understanding of how various visual effects can influence aeronautical decision-making.