4. Depth Perception Flashcards
(20 cards)
What is binocular disparity and how does it contribute to depth perception?
The horizontal positional difference of an object’s image on the two retinas due to eye separation
Fused into a single percept when disparity lies within Panum’s fusional area
What defines the horopter, crossed disparity, and uncrossed disparity?
Horopter: Locus of points with zero disparity (same retinal location)
Crossed disparity: Objects nearer than fixation; images shift outward on each retina
Uncrossed disparity: Objects beyond fixation; images shift inward
How does relative disparity magnitude change with viewing distance?
For a fixed depth separation, nearer objects produce larger relative disparities than farther ones
Tags: Binocular Disparity, Glennerster et al. 1998
Study Reference:
Authors & Year: Glennerster, Rogers & Bradshaw (1998)
Method: Psychophysical measurement of disparity at varying distances
Key Finding: Relative disparity decreases as absolute viewing distance increases
Name three ways to present stereoscopic images to the two eyes.
Stereoscopes (dual peep holes)
Anaglyphs (red–green filtered glasses)
Polarized 3D glasses in film projection
How do random dot stereograms (RDS) generate a depth percept?
Two identical dot fields with a region shifted horizontally in one image
Disparity in the shifted region produces a perceived 3D shape
Tags: Stereopsis, Bela Julesz
Study Reference:
Authors & Year: Julesz (1960s)
Method: Psychophysical demonstration using RDS
Key Finding: Depth perception can arise purely from disparity without monocular cues
What characterizes disparity tuning in visual cortical neurons?
Cells exhibit preferred disparities (crossed vs. uncrossed) with Gaussian-like tuning curves
Tags: Neural Processing, Disparity Tuning
Study Reference:
Authors & Year: Tanabe et al. (2005)
Method: Single-unit recordings in macaque visual cortex
Key Finding: Distribution of preferred disparities spans both crossed and uncrossed ranges
Which cortical areas show selectivity for binocular disparity?
Primary visual cortex (V1) through extrastriate areas (e.g., V2, MT, IT)
Tags: Neural Processing, Stereopsis
Study Reference:
Authors & Year: Bridge & Parker (2007)
Method: fMRI mapping of disparity-selective regions
Key Finding: Disparity processing is distributed across dorsal and ventral streams
How does motion parallax provide monocular depth information?
Observer movement causes nearer objects to traverse the retina faster than distant ones
Relative retinal displacement quantifies object distance
What is the kinetic depth effect?
Motion of a rigid object (e.g., rotating sphere) induces vivid 3D shape perception even without other cues.
How does defocus blur inform about object slant?
Variations in blur gradient across a surface correlate with its slant relative to the focal plane
Active area of ongoing research for 3D shape inference
What perceptual inference does an occlusion cue provide?
When one object blocks part of another, the occluding object is closer to the observer.
How do relative size and Emmert’s Law relate depth and perceived physical size?
Equal retinal image sizes imply that the farther object must be larger in physical size
Emmert’s Law: perceived size ∝ viewing distance when retinal image size is constant
What does linear perspective cue signal?
Convergence of parallel lines toward a vanishing point indicates increasing depth along that axis.
How does texture gradient function as a depth cue?
Uniform textures appear denser and smaller with increasing distance, indicating surface slant or recession.
What produces the aerial (atmospheric) perspective effect?
Scattering of light by fine particles makes distant objects look hazy and bluish (Rayleigh scattering).
Tags: Pictorial Cue, A
How do shading and cast shadows convey 3D shape and depth?
Shading gradients imply surface curvature under assumed light-from-above
Cast shadows indicate spatial relationships between objects
What defines a forced perspective illusion like the Ames room?
Deliberate distortion of physical environment shape
Monocular viewing (“peephole”) enforces a misleading 2D projection, altering size judgments
Tags: Illusion, Forced Perspective
Study Reference:
Authors & Year: Ames (1946)
Method: Architectural manipulation viewed monocularly
Key Finding: Apparent size and depth can be dramatically misperceived
What causes the hollow-face illusion?
Top-down assumption that faces are convex causes a concave mask to be perceived as a normal convex face
Authors & Year: Hill & Johnston (2007)
Method: Presentation of concave masks under variable illumination
Key Finding: Cognitive priors override binocular and shading cues
How does the visual system combine multiple depth cues?
Weights each cue by its reliability (inverse variance) to form a statistically optimal estimate
Tags: Cue Integration, Reliability
Study Reference:
Authors & Year: Jacobs (2002)
Method: Review and modeling of cue weighting experiments
Key Finding: Near-optimal Bayesian-like integration of depth cues
What are key milestones in the development of depth perception?
3–6 months: Emergence of stereopsis and sensitivity to pictorial cues
6–14 months: Avoidance on visual cliff indicates depth sensitivity
Tags: Development, Depth Perception
Study Reference:
Authors & Year: Gibson & Walk (1960)
Method: Visual cliff avoidance in infants
Key Finding: Depth perception evident by 6 months via avoidance behaviour
