outline chap. 3 visual perception unconscious inferences preattentive organization
DESCRIPTION
10/31/2014. Outline Chap. 3 Visual Perception Unconscious inferences Preattentive organization Retinal vs. cortical effects Gathering Visual information Visual Sensory Memory. Study Questions. Describe the unconscious inference theory of Helmholtz. How - PowerPoint PPT PresentationTRANSCRIPT
• Outline» Chap. 3
◊ Visual Perception– Unconscious inferences– Preattentive organization – Retinal vs. cortical effects
– Gathering Visual information
– Visual Sensory Memory
Study Questions.Describe the unconscious inference theory of Helmholtz. How does the theory explain some visual illusions?Describe the gestaltist principles of groupingDefine visual sensory memory. How did Sperling empirically distinguish between a capacity and a duration hypothesis.
04/20/23
Perception and Pattern Recognition
• Visual Perception
Perception and Pattern Recognition
• Visual Perception
Perception
• Perception is in the brain» Melzak : “Pain is in the brain”
◊ Phantom limb pain
» Filling in the blind spot» Complimentary colour mixing» Visual illusions
◊ E.g., The moon illusion
◊ Other illusions
Perception
• The unconscious inference theory (helmholtz)» Analyze cues in sensory input
» Construct a perception with depth, size and motion.
» Send perception on to conscious mind.
• The Müller-Lyer illusion
Perception
• Problems with the unconscious inference explanation.
Perception
• The frame illusion
Perception
» Assimilation theory: We incorporate nearby elements into an object’s boundary when assessing size.
Online Demo
Perception
• Size illusions based on linear perspective
Chasing illusion
Example 1
A great size constancy illusion: The power of persective
Shadow and ball illusion
Coding of Contrast and Contour
• Three examples of exaggerated contrast
Coding of Contrast and Contour
• Receptive fields and on-off areas
-
-- - -
-
-
-----
-
+ + + +
• Contrast heightening
Hermann - Hering grid
• Receptive fields and the Hermann-Hering illusion
Gestalt Perception
• Sensation and bottom-up processing
• “The whole is greater than the sum of its parts”
-> Perception involves an interplay between bottom-up and top-down processes.
• Context and top-down processing.
• Pitting the gestalt against sensation
• Illusions deriving from top-down processing
Gestal principles of grouping
• Proximity.
Gestal principles of grouping
• Similarity.
Gestal principles of grouping
• Closure.
Gestal principles of grouping
• Good continuation.
Online Demo
Figure/ground
• We divide a visual scene into figure (the object to which we attend) and ground (background).
Example 1:
Example 2: Figure and Ground in MC Escher’s art.
Example 3:
Rubin Vase by Shigeo Fukuda
Perception and Pattern Recognition
• Visual auras and migraine headaches» Cortical or retinal?
◊ A retinal effect:
Perception and Pattern Recognition
• Visual auras and migraine headaches» Cortical or retinal?
◊ A retinal effect:
◊ A cortical effect:
Perception and Pattern Recognition
• Extracting visual information» Saccades - eye movements, which occur in a jerking,
start-stop fashion.
Perception and Pattern Recognition
• Visual sensory memory» Visible persistence» Selection from brief displays
H L B M
Q Y X S
E T W R
F Z N Q
W U C D
R Y E T
G X M W
E I V F
T U R Y
Perception and Pattern Recognition
• Visual sensory memory» Visible persistence» Selection from brief displays
» Original findings◊ Observers remember 4 or 5 items (span of apprehension)◊ Sperling’s question: Where is the limitation?
– Capacity hypothesis: The visual system only registers 4 or 5 items– Duration hypotheis: All the letters get registered but fade rapidly
◊ The partial report procedure– E.g., Standing’s experiment
George Sperling
Perception and Pattern Recognition
• Visual sensory memory» Sperling’s results
Cue Delay (Seconds)Full
Report
0 .15 .30 1.0
0
2
4
6
8
10
Est
imat
ed #
lette
rs a
vaila
ble
Perception and Pattern Recognition
• Visual sensory memory» Visual Masking» Averbach and Coriell (1961)
◊ Two types of cues: Bar markers and circles◊ Partial report of 1 item.
J V W RT P N H
Y Q M XS O K I
J V W RT P N H
Y Q M XS O K I
Perception and Pattern Recognition
• Visual sensory memory» Averbach and Coriell (1961)
Cue Delay (ms)
0 100 200 300
0
20
40
60
80
100
Per
cent
age
Cor
rect
-100 400 500
Bar probe
Circle probe
Perception and Pattern Recognition
• Visual sensory memory» Is selection from VSM precategorical?
◊ Merikle (1980)
◊ Demo
H 6 B M
8 Y X S
E 7 W 9
Perception and Pattern Recognition
• Visual sensory memory» Is selection from VSM precategorical?
◊ Merikle (1980)
◊ Demo
A
R
8
T
A
R
G
T
3 6
G5
8
3 6
5
Correlated physical dimension
Present Absent
Perception and Pattern Recognition
• Visual sensory memory» Is selection from VSM precategorical?
◊ Merikle (1980)
◊ Demo
Correlated Physical Dimension
Present Absent
Partial
Whole
6.4
4.4
5.5
4.2
Perception and Pattern Recognition
• Visual sensory memory» Literal representation
◊ Template matching
Perception and Pattern Recognition
• Visual sensory memory» Other issues
◊ Ecological validity