Monocular cues require which of the following?

• A. Two eyes
• B. Depth via movement
• C. Color cues
• D. One eye

Answer: (D)

Monocular cues are depth cues you can use with one eye. This means you don’t need both eyes to judge distance—the brain can infer depth from information available to a single eye. Examples include relative size, which makes distant objects seem smaller; interposition, where an object that covers part of another is perceived as closer; linear perspective and texture gradient, where parallel lines appear to converge and textures become finer with distance; and shading or shadows that reveal surface shape. Motion-related depth, like motion parallax, can also be perceived with one eye when you or the scene move, since nearer objects shift position on the retina more quickly than farther ones. Because these cues rely on one-eye information, they’re categorized as monocular cues. In contrast, depth cues that require both eyes—such as retinal disparity and convergence—are binocular cues. Color cues by themselves don’t reliably provide depth information, though color can aid interpretation of scenes in combination with other cues.