Which of the following is a monocular depth cue?

• A. Motion Parallax
• B. Binocular Disparity
• C. Stereopsis
• D. Convergence

Answer: (A)

Depth perception can be inferred from cues that work with one eye, and motion-based cues are a classic example. As you move, objects at different distances appear to slide across your field of view at different speeds: nearer objects move faster, farther ones move slower. This relative motion, observed with just one eye and some head or body movement, is motion parallax. It’s especially reliable when you’re moving through a scene, like walking past trees, buildings, or fence posts—the closer ones sweep by quickly while distant ones barely move.

The other options rely on information from both eyes. Binocular disparity and stereopsis come from the two slightly different images each eye receives, enabling depth via stereo vision. Convergence involves the inward turning of the eyes to focus on a near object and uses binocular coordination to judge distance. Since these require both eyes, they aren’t monocular cues.