Bruce is a notable case of someone who lived without stereovision for most of his life. Because his cells responsive to binocular depth cues survived, experts assume he experienced at least a fleeting moment of binocular vision during early development. Nearly 70 years later, these cells were successfully activated when he put on 3-D glasses at a movie theater, allowing him to experience true depth perception.

Bruce's Late-Onset Depth Perception

Cells in the nervous system that respond to binocular depth cues typically require activation during early development in order to persist. If they are activated even fleetingly during this critical period, the cells can survive and be utilized for depth perception much later in life.

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Binocular cues are visual signals used to perceive depth that depend on the simultaneous use of both eyes. By integrating the slightly different information received from each eye's unique vantage point, the brain can establish a sense of three-dimensional space.

Binocular Cues

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

As a primary example of a binocular cue, binocular disparity refers to the subtle difference between the visual images that each eye receives. Because the eyes are horizontally separated, they capture slightly different views of the world, and the brain uses this disparity to compute depth.

Binocular Disparity

Stereoblindness is a condition characterized by the inability to use binocular cues to perceive depth. Individuals with this condition must depend solely on monocular cues to interpret the three-dimensional world.

Stereoblindness

The nervous system possesses specialized cells that respond to binocular depth cues. For these cells to be maintained and function later in life, they must be activated by visual input during a critical period in early development.

Neural Persistence in Binocular Vision Development

Based on the principles of depth perception, explain why the task described in the case study becomes much harder when performed with only one eye open.

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