Cognitive Psychology, Fifth Edition, Robert J. SternbergChapter 3
Chapter 3: Visual Perception
Ted talk: beau lotto: optical illusions 2009
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Some Questions of Interest• What is sensation vs. perception?• What are two fundamental approaches
to explaining perception? • What happens when people with normal
visual sensations cannot perceive visual stimuli?
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
• Light waves• Sound waves
• Chemical molecules
• Chemical molecules
• Pressure/vibration
• Photon absorption• Conduction to basilar
membrane• Absorption in
olfactory epithelium• Contact with taste
buds• Stimulation of dermis
receptor cells
Distal vs. proximal stimuli
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Our Visual System
Electromagnetic light energy is converted into neural electrochemical impulses
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Our Visual System
Three main layers of retina– Ganglion cells– Amacrine cells, horizontal
cells, bipolar cells– Photoreceptors
• Rods and cones
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Visual Pathways in the Brain“what”
• Temporal lobe lesions in monkeys
– Can indicate where but not what
“where” – Parietal lobe
lesions in monkeys– Can indicate
what but not where
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Sensation does not equal perception!
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Perceptual Basics• Sensory adaptation
– Occurs when sensory receptors change their sensitivity to the stimulus
• Our senses respond to change– Ganzfeld effect
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Perceptual Constancy• Object remains the same even
though our sensation of the object changes– Size constancyvs. shape
constancy
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Depth Perception– Monocular vs. binocular depth cues
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
• Texture gradients– Grain of item
• Relative size– Bigger is closer
• Interposition• Closer are in front of other objects• Linear perspective
– Parallel lines converge in distance
• Aerial perspective– Images seem blurry farther away
• Motion parallax– Objects get smaller at decreasing speed in distance
Monocular Depth Cues
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Binocular Depth Cues• Binocular convergence• Binocular disparity
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Perceptual Illusions• Sometimes we cannot
perceive what does exist
• Sometimes we perceive things that do not exist
• Sometimes we perceive what cannot be there
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Perceptual Illusions
http://www.michaelbach.de/ot/#history
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Visual illusions: brain function
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Theories of Perception• Bottom-up vs top down theories
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Bottom-Up Processing Theories• Direct perception• Template theories• Feature-matching theories• Recognition-by-components theory
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Gibson’s Theory of Direct Perception
• The information in our sensory receptors is all we need– No complex thought processes
• EX: Use texture gradients as cues for depth and distance
• Mirror neurons start firing 30-100 ms after a visual stimulus
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Template Theoriescompare to templates in memory until a match is found
– Problem of imperfect matches
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Feature-Matching Theories• Recognize objects by features
– Detect elements and assemble them into more complex forms
– Brain cells respond to specific features• lines and angles
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Pandemonium Model
• Four kinds of demons– Image demons– Feature demons– Cognitive demons– Decision demons
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
• Hubel & Wiesel (1979) – Simple cells – bars/edges– Complex cells –
bars/edgesdetect bars of particular orientation
– Hypercomplex cells -- particular colors (simple and complex cells), bars, or edges of particular length or moving in a particular direction
Physiological Evidence for Features
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
CogLab: Visual Search
• Features vs. objects• The role of attention (next chapter)
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Top-Down Processing (Constructive Approach)
• Perception is not automatic from raw stimuli– making inferences– guessing from experience
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
“Finished files are the result of years of scientific study combined with the experience of many years.”
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
•Context effectsContext helps us to be able to recognize letters in many different styles.Context helps us to be able to recognize letters in many different styles.Context helps us to be able to recognize letters in many different styles.
Evidence for Top-Down Processing
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Configural-Superiority Effect• Objects presented in context are easier to
recognize than objects presented alone• Task: Spot the different stimuli, press button
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Configural-Superiority Effect
Measure reaction timeTarget alone = 1884 Composite = 749Target spotted faster in a context!
Target Composite
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Gestalt’s View of Perception“The whole is more than a sum of its parts”
• Law of Prägnanz–Individuals organize their experience in as simple, concise, symmetrical, and complete manner as possible
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Gestalt’s Principles of Visual Perception
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Gestalt’s Principles of Visual Perception
• Figure-ground– Organize perceptions by
distinguishing between a figure and a background
• Proximity– Elements tend to be grouped
together according to their nearness
• Similarity– Items similar in some respect tend
to be grouped together
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Gestalt’s Principles of Visual Perception
• Continuity– Based on smooth continuity,
which is preferred to abrupt changes of direction
• Closure– Items are grouped together if
they tend to complete a figure • Symmetry
– Prefer to perceive objects as mirror images
C
B
A
D
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Pattern Recognition Systems• Feature analysis system
– Recognize parts of objects– Assemble parts into wholes
• Configurational system– Recognize larger configurations
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
• Tanaka & Farah (1993)– Participants studied
• Faces and names• Pictures of homes and home owner’s names
– At test, given only a piece of face (e.g., nose), whole face, whole home, or a piece of the home (e.g., window)• Asked to recall names
Evidence for Separate Systems
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Tanaka & Farah (1993)• People have more difficulty recognizing
parts of faces than parts of houses
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Fusiform Gyrus in Temporal Lobe
• pattern recognition– facial recognition– high expertise in any item (birds,
cars) recognition– Expert individuation hypothesis
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
• Prosopagnosia– Inability to recognize faces after brain
damage– Ability to recognize objects is intact
• Associative agnosia– Difficulty with recognizing objects– Can recognize faces
Evidence for Separate Systems
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Deficits in Perception• Disruption of the “what” pathway
– Agnosia: Inability to recognize and identify objects or people
• Disruption of the “what” pathway– Simultagnosic
• Normal visual fields, yet act blind• Perceives only one stimulus at a time—single word or
object
• Prosopagnosia• Inability to recognize faces, including one's own
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Visual Pathways in the Brain“what”
• Temporal lobe lesions in monkeys
– Can indicate where but not what
“where” – Parietal lobe
lesions in monkeys– Can indicate
what but not where
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Deficits in Perception• Disruption of the “how” pathway
– Optic ataxia• Cannot use vision to guide movement• Unable to reach for items
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Synesthesia Michael: “Flavors have shape,” he started, frowning into the depths of the roasting pan. “I wanted the taste of this chicken to be a pointed shape, but it came out all round. … When I taste something with an intense flavor,” Michael continued, “the feeling sweeps down my arm into my fingertips. I feel it—its weight, its texture, whether it’s warm or cold, everything. I feel it like I’m actually grasping something.” (p. 4)
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Synesthesia Victoria:In response to a pager going off, said: “Oh, those blinding red jaggers! Turn that thing off,” she snapped. … “Your beeper made me see three red lightning bolts, brilliant red going up to the left.” She kept rubbing her head. “It’s usually not that strong, but it’s given me a splitting pain,” she continued. (pp. 47-48). “What makes you see things?” I asked. “Give us some details.” “Sharp, shrill sounds always do it,” she said, “like your beeper, or ambulance sirens, crashes, screeching tires.” … “Sudden sounds like that. Sometimes music will do it, if it’s loud enough and high enough in pitch,” she continued. … “I once heard a Chihuahua who drove me crazy with the sound of white spikes. But that can’t be the correct explanation, because words and names sometimes have color too.” (p. 48)
Cognitive Psychology, Sixth Edition, Robert J. SternbergChapter 3
Perceptual Illusions and “construction”
• Phantom limb• synesthsia