PERCEPTION EXAM 4 - DEPTH perception

What is the PROBLEM in DEPTH PERCEPTION? What is the ANSWER to this problem?

• Problem = How do we perceive a 3D world when the retinal image is 2D?

• Answer = Because Depth is a Perception

What are the TWO TYPES OF CUES in depth perception?

1. Binocular cues (stereopsis)

2. Monocular cues

What is BINOCULAR VISION (STEREOPSIS)? What TWO THINGS does it DEPEND ON?

• Perceiving a 3D World (Depth)

• DEPENDS ON:

1. Disparity

2. Convergence

What is BINOCULAR CONVERGENCE in DEPTH PERCEPTION? What OBJECTS create the GREATEST CONVERGENCE? How BIG of a cue is it?

• Different Muscular Tensions when Eyes Converge upon an Object

• CLOSER Objects = greater Convergence & stronger Neural Feedback

• Relatively minor cue

What is BINOCULAR DISPARITY in DEPTH PERCEPTION? How BIG of a cue is it? What does it CREATE?

• Different retinal image from each eye

• MAJOR binocular cue

• Creates THE HOROPTER

What is the HOROPTER? Where does BINOCULAR DISPARITY occur in the HOROPTER?

• Imaginary Line where certain images fall on corresponding retinal points

• Binocular Disparity occurs from Objects in Front of and Behind the Horopter

What is the RELATIONSHIP between IMAGES and DISTANCE FROM HOROPTER?

• Further from the Horopter = Greater Binocular Disparity

What is the CODING MECHANISM for DEPTH PERCEPTION?

• Retinal disparity (the slightly differing images in each eye)

What CELLS respond to RETINAL DISPARITY? WHERE are the located? What TWO DISPARITIES do they respond to? WHERE do these disparities take place?

• BINOCULAR CELLS in V1 CORTEX

• Respond to: 

1. CROSSED DISPARITY (before horopter)

2. UNCROSSED DISPARITY (after horopter)

What PATHWAY codes for BINOCULAR DISPARITY? What 3 THINGS does it ASSIST with?

• DORSAL STREAM PATHWAY

• Assists with: 

1. SPATIAL POSITIONING 

2. GUIDING MOVEMENTS

3. HAND-EYE COORDINATION

How does the DORSAL STREAM PATHWAY assist with HAND-EYE COORDINATION (2 ways)?

1. Provides map of visual field

2. Detecting/analyzing movements

What are the 4 DISORDERS associated with POSTERIAL PARIETAL CORTEX?

1. Sensory neglect (inability to perceive one half of the perceptual world (usually left)). 

2. Motion Blindness (inability to perceive motion)

3. Simultanagnosia (Inability to perceive multiple objects simultaneously)

4. Optic ataxia (inability to use visuospatial information to guide arm movements.)

5. Apraxia (inability to produce volitional movement in the absence of muscular disorders)

What are the NINE CUES of MONOCULAR VISION in DEPTH PERCEPTION? (IRLTHLAMF)

1. Interposition (overlap)

2. Aerial perspective (haziness as distance cue–atmospheric blur)

3. Lighting & shading (distance inferences)

4. Height in visual field (higher in field = more distant)

5. Linear Perspective (Convergence of Parallel Lines with Increasing Distance)

6. Texture Gradient (Changes in Texture with Increasing Distance)

7. Familiar Size (Image Size to Perceive Distance)

8. Relative Size (Objects with a Larger Retinal Image are Perceived as Closer)

9. Motion Parallax (Objects at Different Distances Move at Different Speeds)

What ILLUSION does LINEAR PERSPECTIVE create? WHAT’s the illusion?

• The PONZO ILLUSION: a size-perception illusion where two identical horizontal lines are perceived as different lengths

What is the AMES ROOM? What EFFECT creates it? What 2 THINGS does it DEPEND on? WHO invented it? What is its TAKEAWAY MESSAGE?

• Distorted room which manipulates distance cues to create the illusion–created by RELATIVE SIZE EFFECT

• DEPENDS ON size constancy & top-down processing.

• INVENTED BY American ophthalmologist Adelbert Ames, Jr. in 1934

• We use distance-related context cues to help us interpret the size of objects

What ARTIST toyed with MONOCULAR CUES?

• M.C. Escher