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Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Chapter 4: Perception
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Perception Is…
• The process of recognizing, organizing and interpreting information
• How do you recognize these items?
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Perceptual Basics
• Sensory Adaptation– Occurs when sensory receptors change
their sensitivity to the stimulus
– Constant stimulation leads to lower sensitivity
• Our senses respond to change
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Perceptual Basics
• Perceptual Constancy– Object remains the
same even though our sensation of the object changes
• Example: – Shape constancy
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Depth Perception• The ability to see the world in 3 dimensions
and detect distance– Vision only has a 2-dimensional view
– We must interpret the information given to perceive depth
– We take flat images and create a three dimensional view
– Optical illusions demonstrate that this interpretation does not always have to be correct
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
• Texture Gradients– Grain of item
• Relative Size– Bigger is closer
• Interposition– Closer are in
front of other objects
Monocular Depth Cues
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Monocular Depth Cues
• Linear Perspective– Parallel lines
converge in distance
• Aerial Perspective– Images seem blurry,
the farther away
• Motion Parallax– Objects get smaller
at decreasing speed in distance
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Binocular Depth Cues
• Binocular Convergence– Eyes turn inward as object moves
towards you, brain uses this information to judge distance
• Binocular Disparity– Each eye views a slightly different angle
of an object; Brain uses this to create a 3-d image
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Object Perception
• Viewer-centered representation – Object is stored in the perspective seen– Store multiple views of object as seen under
various conditions – Viewpoint dependent process
• Object-centered representation – Object is stored in a way that best represents the
object – Viewpoint invariant process
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Object Perception
• Evidence supports both
• How to reconcile?– Maybe both contribute to object
recognition– Two ends of a continuum that contribute
to object recognition– Burgund & Tarr researched this issue
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Gestalt’s View of Perception
• Basic Tenet– “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, Fourth Edition, Robert J. SternbergChapter 4
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, Fourth Edition, Robert J. SternbergChapter 4
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 imagesKanizsa's Figure
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D
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Theories of Perception
• Direct Perception theories– Perception comes from the stimuli in the
environment– Bottom up processing – Parts are identified, put together, and then
recognition occurs
• Constructive Perception theories– People actively construct perceptions using
information based on expectations– Top down processing
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Gibson’s Direct Perception (Ecological model)
• All the information needed to form a perception is available in the environment
• Perception is immediate and spontaneous
• No top down processing is necessary
• Perception and action cannot be separated
• Perception guides action and action generates more new perceptual information
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Bottom Up Processing Theories
• Template theories
• Prototype theories
• Feature theories
• Structural description theories
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Template Theory
• Basics of template theory– Multiple templates are held in memory
– To recognize the incoming stimuli, you compare to templates in memory until a match is found
See stimuli
Search memory for a match
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Template Theory
• Weakness of theory– Problem of imperfect matches
– Cannot account for the flexibility of pattern recognition system
See stimuli No perfect match in memory
Search for match in memory
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Prototype Theories• Modification of template matching
(flexible templates)
• Takes various instances of an object and abstracts out the common characteristics
• No match is perfect; a criterion for matching is needed
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Prototype Evidence
• Franks & Bransford (1971)– Presented objects based on prototypes
– Prototype not shown
– Yet participants are confident they had seen prototype
– Suggests existence of prototypes
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Prototype Evidence
• Solso & McCarthy (1981)– Participants were shown a
series of faces
– Later, a recognition test was given with some old faces, a prototype face, and some new faces that differed in degree from prototype
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Solso & McCarthy (1981) Results
• The red arrow notes that participants were more confident they had seen the prototype than actual items they had seen
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Research on Prototypes
• Researchers have found that prototypical faces are found to be more attractive to participants
• Halberstadt & Rhodes (2000)– Examined the impact of prototypes of dogs,
wristwatches, and birds on attractiveness of the stimuli
– Results indicate a strong relationship between averageness and attractiveness of the dogs, birds, and wristwatches
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Feature Theories
• Recognize objects on the basis of a small number of characteristics (features)– Detect specific elements and assemble them
into more complex forms
– Brain cells that respond to specific features, such as lines and angles are referred to as “feature detectors”
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Feature Evidence
• Hubel & Wiesel (1979) using single cell technique– Simple cells detect bars or edges of particular
orientation in particular location – Complex cells detect bars or edges of
particular orientation, exact location abstracted – Hypercomplex cells detect particular colors
(simple and complex cells), bars, or edges of particular length or moving in a particular direction
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Structural-Description Theories
• Biederman (1987)– Describes how 3D
images are identified
– Breaks objects down into geons
– Objects are identified by geons and relationship between them
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Evidence of Geons•Beiderman (1987) Can you identify these objects?
These objects have been rendered unidentifiable because their geons are nonrecoverable
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Evidence of Geons• Beiderman (1987)
• Can you identify these objects?
These objects have had the same amount of the object taken out but because the geons can still be recreated, one can recover the objects
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Evidence for Geons
• Beiderman (1987) demonstrated the importance of the use of geons to recognize objects
Original Recoverable Nonrecoverable
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Evidence for Geons
• Biederman & Cooper (1991)– Used visual priming to demonstrate the
existence of geons in a picture naming task– Subjects were shown a series of fragmented
pictures and were asked to identify the objects
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Biederman & Cooper (1991)
After naming novel objects, the second phase begins …
Name these fragmented objects
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Biederman & Cooper (1991)
1st fragment Complementary fragment Different exemplar
Several different kinds of stimuli were used: identical repeats, complementary, novel, and different exemplars. Reaction time to name object was noted.
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Biederman & Cooper (1991) ResultsReaction time for identical and complementary stimuli was faster demonstrating visual priming.
Visual priming could only occur if participants had created the whole geon when exposed to the first fragmented image.
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Top-down Processing (Constructive Perspective)
• Perception is not automatic from raw stimuli
• Processing is needed to build perception
• Top down processing occurs quickly and involves making inferences, guessing from experience, and basing one perception on another
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Top-down Processing Evidence
•Context effects
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.Context helps us to be able to recognize letters in many different styles.
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Palmer (1975) Context Effect•Showed participants a related scene, an unrelated scene, or no context•Immediately after, asked participants to name a briefly seen object •Objects that were appropriate to the scene (or context)•were recognized more rapidly than objects that were unrelated to the scene
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Marr’s Computational Theory
edgescontours
blobs
edgescontours
blobs depth&
orientation
depth&
orientationreal shapereal shape
2-D Primal sketch
2.5-D Sketch3-D model
representation
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Deficits in Perception
• Agnosia– Inability to recognize and identify objects
or persons despite having knowledge of the characteristics of the objects or persons
– Shows the specialization of our perceptual systems
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Perceptual Deficits• Prosopagnosia
– Inability to recognize faces, including one's own
– Cannot recognize person from face– Knows a face is a face – Can recognize individuals from voice – Can recognize objects– Can discriminate whether two faces are
same or different
Cognitive Psychology, Fourth Edition, Robert J. SternbergChapter 4
Deficits in Perception• Simultagnosic
– Normal visual fields, yet act blind
– Perceives only one stimulus at a time—single word or object