Depth perception

psych 367

Question

Answer

What is depth perception?

The ability to perceive the world in three dimensions and judge the distance of objects

What is absolute distance judgment?

Egocentric localization: judging distance from oneself to an object

What is relative distance judgment?

Object-to-object comparison of distances between objects

What are monocular depth cues?

Depth cues available from one eye alone

What are pictorial depth cues?

Monocular cues that can be extracted from a 2D image

What is occlusion?

When one object overlaps another

What assumption underlies shading and shadows?

The brain assumes light comes from above

What do shading and shadows provide?

Information about surface orientation and depth

What is atmospheric perspective?

Distant objects appear blurrier and more blue due to scattering of light

What is relative size?

Objects of the same size appear smaller when farther away

What is familiar size?

Knowledge of an object's real size influences perceived distance

What is linear perspective?

Parallel lines appear to converge at a vanishing point with distance

What is the vanishing point?

The point at which parallel lines appear to meet in the distance

What is the horizon in linear perspective?

The line where the sky meets the ground and where vanishing points lie

What is one-point perspective?

All lines converge to a single vanishing point

What is two-point perspective?

Lines converge to two vanishing points

What was Brunelleschi’s contribution?

Demonstrated linear perspective using a mirror and painting experiment

What was Alberti’s grid?

A technique to accurately copy scenes by dividing them into squares

Why is Alberti’s grid important?

It reduces top-down bias and improves realistic drawing

What is relative height as a depth cue?

Objects higher in the visual field (below horizon) appear farther away

What is texture gradient?

Textures become smaller and denser with distance

Why is texture gradient considered a higher-order cue?

It combines relative size and linear perspective

What is motion parallax?

Nearby objects move faster across the visual field than distant objects during observer motion

What is deletion?

A background object becomes hidden by a moving foreground object

What is accretion?

A background object is revealed as a foreground object moves away

What are oculomotor depth cues?

Depth cues based on eye movement and lens adjustment

What is accommodation?

Change in lens shape to focus on objects at different distances

How does accommodation signal distance?

Ciliary muscle feedback indicates lens curvature and distance

What is convergence?

Inward rotation of the eyes to focus on near objects

How does convergence signal depth?

Larger angle = closer object; smaller angle = farther object

What is the limitation of oculomotor cues?

They are only effective within about 2 meters

How do depth cues interact?

They combine additively to improve accuracy

What happens when more depth cues are present?

Depth perception becomes stronger and more accurate

What is stereopsis?

Depth perception based on binocular disparity

What is retinal disparity?

Difference in images between the two eyes

What is the horopter?

Imaginary surface where objects produce no retinal disparity

What happens if an object is on the horopter?

It falls on corresponding retinal points (no disparity)

What happens if an object is off the horopter?

It produces retinal disparity

What determines the amount of disparity?

Distance from the horopter

What is a random-dot stereogram?

A pattern where disparity is artificially created to produce depth perception

How do random-dot stereograms work?

A shifted region creates disparity

What is a SIRDS (autostereogram)?

A single image that produces depth perception when viewed with altered convergence

How do SIRDS differ from random-dot stereograms?

They use one image instead of two separate images

What is the correspondence problem?

Determining which features in each eye match to form a single percept

What is Marr & Poggio’s solution?

Matching based on similarity between features

Why is the correspondence problem difficult?

There is no universally accepted solution

What did Holway & Boring study?

How size perception depends on depth cues

What happens under normal viewing conditions?

Perceived size matches actual object size

What happens when depth cues are removed?

Perceived size depends on retinal image size

What is visual angle?

The size of an image on the retina

What did Bruner & Goodman find?

Valuable objects (coins) are perceived as larger

What does this suggest about perception?

Top-down processing influences size perception

What is size constancy?

Perceiving objects as constant in size despite changes in distance

What is size-distance invariance?

Retinal size decreases with distance but perceived size remains constant

What is size-distance scaling?

Using distance cues to interpret size

What causes errors in size perception?

Lack of depth cues

Why do illusions occur?

Misapplication of size constancy mechanisms

What is the Müller-Lyer illusion?

Lines appear different lengths due to arrow-like endings

What is the carpentered world hypothesis?

Exposure to right angles affects susceptibility to the illusion

Why is the illusion weaker in some cultures?

Less exposure to rectangular environments

What is the moon illusion?

The moon appears larger on the horizon than overhead

Why is the moon illusion not due to actual size?

Retinal size remains constant

What is the apparent-distance theory?

Horizon appears farther

What did Holway & Boring find about the moon illusion?

People perceive the horizon moon as closer

What is the eye elevation hypothesis?

Looking upward makes objects appear smaller

What evidence supports eye elevation hypothesis?

Moon appears larger when viewed at eye level

What did Kaufman & Rock argue?

Size-distance relationship is unclear and difficult to measure

What is Emmert’s Law?

Perceived size is proportional to perceived distance

How does Emmert’s Law apply to the moon illusion?

Farther perceived moon appears larger

What is the “flattened sky” theory?

The sky appears like a flattened dome

How might clouds contribute to the illusion?

They make the sky appear like a surface

What is human factors and ergonomics?

Designing systems based on human perception and behavior

What is the goal of ergonomics?

Safety

What is the speed-size illusion?

Larger objects appear to move more slowly

Why do trains seem slow?

Large size reduces perceived motion speed

What is the illusion of linear perspective in driving?

Parallel lines make objects appear farther away

What is looming?

Increase in visual angle as an object approaches

Why is looming misleading?

It increases nonlinearly

What is deceptive geometry of collisions?

Visual angle increases exponentially as distance decreases

Why do people misjudge train arrival?

They overestimate time due to nonlinear visual expansion

What are solutions to rail crossing accidents?

Education

What is Operation Lifesaver?

A safety campaign to reduce train collisions

Why can’t basic perception be changed?

It is biologically hardwired

What is a potential engineering solution?

Enhancing perceived speed using lights or markings