Development & Stages of Depth Perception

Depth perception refers to the ability to see and understand the 3-D spatial relationship and relative distance between objects and oneself. Its primary value is to make hand-eye coordination efficient and provide for safe movement through space. Infants are born with an immature vision system that gradually develops to take in better and more precise visual information while the brain learns to look for cues gleaned from experience.

  1. Physiology

    • The retina is the curved two-dimensional surface at the back of the eye containing photoreceptor cells called rods and cones. Cones perceive color, fine detail and respond rapidly to stimuli so they can register changes to images quickly. Signals travel from the retina to the visual cortex of the brain, which develops as it learns to interpret the 2-D images it receives and use their messages to recreate the 3-D world. Infants are attracted by movement and instinctively seek stimulation that gives them the cues they need to develop depth perception.

    Monocular Cues

    • Monocular cues are those detected with one eye. Babies begin learning their meanings before their eyes start tracking together. Types of monocular cues include motion parallax cues that teach the infant that as he moves, closer surfaces appear to move farther and faster than distant ones do. (Think of driving down a road lined with trees. The ones close to you zip by faster than the ones in the distance that seem to move more slowly.) Optic flow, revealed at 3 to 4 weeks of age by blinking when an object approaches, teaches babies that moving toward a surface makes things appear bigger and that the reverse is also true. This tells infants in which direction they are moving.

    Binocular Cues

    • Once the infant develops stereoptic vision, at 3 to 4 months old, cues that compare information from the two eyes teach the brain new ways to perceive the dimensionality of space. Each retina sends a slightly different image to the brain, which assesses the degree of this binocular disparity to figure out the image̵7;s depth. Convergence describes the changes in muscular tension when the eyes rotate inward or outward to focus effectively. This feedback provides valuable information on depth when objects are less than 20 feet away.

    Pictorial Cues

    • By 6 months of age, the brain is building knowledge of pictorial cues through observation. Atmospheric perspective, for example, tells the brain that hazy objects are usually farther away than sharp ones. Linear perspective reminds babies that lines (such as railroad tracks) converge as they disappear into the distance. Occlusion tells babies that nearby surfaces or objects overlap far surfaces and distant objects. If the baby sees a whole chair and part of a bookcase, she learns that the chair is in front of the bookcase. By 7 to 10 months, infants̵7; depth perception ability matches that of an adult.

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