What is motion parallax?

Motion parallax is a depth cue that involves the perception of the relative motion of objects as an observer moves through their environment. This phenomenon occurs because objects that are closer to the observer appear to move faster across the visual field than objects that are farther away. As a result, during motion, the brain uses this information to judge distances and depth, perceiving the spatial relationship of objects in a three-dimensional space.

When you are in motion, for instance, if you're walking or driving, nearby objects such as trees or cars seem to zip by quickly, while distant objects such as mountains or buildings appear to move much more slowly. This relative speed difference allows for better spatial perception and aids in navigation.

The other options do not pertain to this concept. The first option relates to the perception of images but does not specifically address depth perception as influenced by motion. The third and fourth options are about memory techniques and do not connect to the visual and perceptual aspects of motion parallax. Thus, the definition that emphasizes the differential perception of speed in relation to distance is the most accurate representation of motion parallax.