Chapter 3: Perceiving Objects & Recognizing Patterns

Question 1

Perception

Answer 1

Take sensory input and interpret it meaningful
Perception of patterns, objects, people, and events

Question 2

Conscious Experience

Answer 2

Active reconstructive process
What you see, hear, and experience does not directly correspond to the stimuli in the world

Question 3

Distal Stimulus

Answer 3

Objects and events in the real world
To process info about this stimuli, must receive info from sensory systems

Question 4

Proximal Stimulus

Answer 4

Reception of info and its registration by a sense organ
E.g. light waves reflect from the trees and cars to eyes (retina)
Retinal image is formed (2D), with size dependent on distance from objects
Retinal images are upside down and reversed

Question 5

Percept

Answer 5

Meaningful interpretation of proximal stimulus

Question 6

Size Constancy

Answer 6

Objects appear smaller farther away, but we know that they are time same size regardless of where we look from
Objects that are farther away take up less space on the retina

Question 7

Pattern Recognition

Answer 7

Recognition of a particular object, event, etc. as belonging to a class of objects, events, etc.
Almost all instances of perception involve pattern recognition
E.g. recognize a bush as part of the shrubs category

Question 8

Gestalt Approaches To Perception

Answer 8

Gestalt psychologists think that we identify objects as a unit or whole
Form perception
Illusory/subjective contours

Question 9

Form Perception

Answer 9

Segregation of the whole into objects (figure) and background (ground)
E.g. reversible figure where you either see two sides of faces or a vase

Question 10

Illusory/Subjective Contours

Answer 10

See a triangle in white space even though there are no lines creating a triangle

Question 11

Gestalt Principles of Perceptual Organization

Answer 11

Proximity
Similarity
Good continuation
Closure
Common fate
Symmetry/Parallelism

Question 12

Proximity

Answer 12

we group things that are closer together (e.g. group A in rows)

Question 13

Similarity

Answer 13

group elements that are similar (e.g. group B in columns)

Question 14

Good Continuation

Answer 14

group objects whose contours form a continuous straight or curved line (e.g. see two intersection lines in C)

Question 15

Closure

Answer 15

perceive shapes even when there are gaps in a figure (e.g. see a rectangle in E)

Question 16

Common Fate

Answer 16

elements that move together will be grouped together (e.g. see F)

Question 17

Law of Pragnanz

Answer 17

of all possible ways of interpreting a display, we use the organization that yields the simplest and most stable shape or form
Most Gestalt principles are subsumed under this law
Simple and symmetric forms are seen more easily
Can help to explain experience with subjective contours
Some principles are used by infants form 3-6 months

Question 18

Issues With Gestalt Approach to Perception

Answer 18

Don’t know how these principles are translated into cognitive or physiological processes
Law of Pragnanz can be seen as circular

Question 19

Bottom-Up Processes

Answer 19

Data Driven/Stimulus Driven
Perceiver starts with small bits of info from environment that are combined in various ways to form a percept
E.g. see edges, rectangular and other shapes, certain lighted regions, put together conclude you see doors and a hallway

Question 20

Three Bottom Up Processes

Answer 20

Template matching
Feature analysis
Prototype matching

Question 21

Template Matching

Answer 21

Correspondence between (external) stimulus and stored pattern in memory (internal template)
A pattern is compared to all templates and identified by the template that best matches it

Question 22

Templates

Answer 22

Previously stored patterns
Need to be an exact match to stimuli
E.g. QR code

Question 23

Problems With template Matching

Answer 23

Need a lot of templates
Does not explain how we recognize new objects (create new templates?)
Does not deal well with surface variation of stimuli (e.g. writing - everyone’s handwriting looks different)

Question 24

Featural Analysis

Answer 24

Processing stimuli by breaking them down into components
Use recognition of parts to infer what the whole represents
Fits the strongest with neurophysiological evidence

Question 25

Objects

Answer 25

Combinations of features

Question 26

Features

Answer 26

Small (local) templates that can be combined in. many different ways

Question 27

Edge Detectors

Answer 27

Cells responding strongly to borders between light and dark (Hubel & Weisel)
There are many other cells specified to respond to different elements of stimuli (e.g. certain orientation of lines)

Question 28

Visual Search Task

Answer 28

Present participants with arrays of letters
Respond if they detected the presence of a particular target
Participants took longer to find a Z than a Q when arrays share features of straight/angular lines
Same has been found for auditory features

Question 29

Advantages of Feature Analysis

Answer 29

More flexible system
Reduced number of (local) templates

Question 30

Issues With Feature Analysis

Answer 30

No good definitions of what can be a feature and what cannot
E.g. what are the features of the face? Specific features for right and left sides or more general? Etc.

Question 31

Prototype Matching

Answer 31

Explain perception in terms of matching an input to a stored representation of info, but the stored representation is a prototype
Matching pattern to stored representation (this time a prototype)
Exact match is not required, only approximate

Question 32

Prototype

Answer 32

idealized representation of some class of objects or events

Question 33

Top Down Processes

Answer 33

Theory Driven/Conceptually Driven
Perceiver expectations, theories or concepts guide the selection and combination of the info in the pattern recognition process
Expectations guided where you look, what you looked at, and how info is put together

Question 34

Problems With Bottom Up Processing

Answer 34

Context & expectation effects
Top down processes have to interact with bottom up processes (otherwise wouldn’t be able to perceive things you weren’t expecting)

Question 35

Context Effects

Answer 35

Accuracy and length of time required to recognize objects vary with context (e.g. recognize utensils quicker when looking at kitchen scene)

Question 36

David Marr’s Model

Answer 36

Primal sketch: depicts areas of relative brightness and darkness in a 2D image as well as localized geometric structure (bottom up processes)
2 ½ D sketch: use shading, texture, edges. Etc viewer derives info about what the surfaces are and how they are positioned (relies on bottom up processes)
3D sketch: info from real world knowledge or specific expectations incorporated (top down processes)

Question 37

Change Blindness

Answer 37

Inability to detect changes to an object or scene especially when given different views of that object or scene
E.g. people are blind to changes in movie scenes where in one scene a child is playing blocks and in other is not, etc.

Question 38

Word Superiority Effect Experiment

Answer 38

Reicher
Participants asked to identify which of two letters was briefly presented on screen
Later, presented with two alternatives for what letter might have been
Sometimes presented with a single letter, sometimes with a word, sometimes with three other letters (did not spell word)
Participants better identified letters presented in context of words than alone or nonwords

Question 39

Word Superiority Effect (Word Advantage)

Answer 39

Letters are easier to perceive in a familiar context (words)

Question 40

Missing Letter Effect

Answer 40

When readers read connected text quickly divide words into content words and function words
Focus attention more on moderately familiar content words, more likely to miss letters in highly familiar function words

Question 41

Connectionist Model of Word Perception

Answer 41

McClelland & Rumelhart
Input is processed at several different levels (e.g. features, letters, phonemes, words)
Many connections (excitatory or inhibitory) between each ‘node’
Once a node is activated, activation spreads along node’s excitatory connections to other nodes
E.g. T node will become more active with the Trap node (for word prediction game)
Explains word superiority

Question 42

Common Assumptions For Perception Models

Answer 42

Perceiver must acquire info about distal stimulus (presumably by interpreting proximal stimuli)
Perceiver does something to the proximal stimuli (probably because it doesn’t contain all the info needed to identify it)
All models describe the act of perception as the construction of mental representations of objects

Question 43

Constructivist Approach to Perception

Answer 43

People add to and distort the info in the proximal stimulus to obtain a percept, a meaningful interpretation of incoming info

Question 44

James Gibson

Answer 44

Rejected the idea that perceivers construct mental representations from memories of past encounters with similar stimuli
Perceiver does little work, because the world offers so much info, leaving little need to construct representations and draw inferences
Central question of perception is not how we look at and interpret a stimulus, but instead how we see and navigate among real things in the world
Direct perception
Affordances

Question 45

Direct Perception

Answer 45

Light hitting the retina contains highly organized info that requires little or no interpretation

Question 46

Affordances

Answer 46

Acts or behaviours permitted by objects, places, and events
E.g. chairs afford sitting, handle affords grasping
Affordances of objects are directly perceived (e.g. we see a chair is for sitting as easily as we see a chair is made of wood)

Question 47

Critiques of Gibsonian theory

Answer 47

Without sharp definitions of affordance, theory is not helpful to explain perception
Gibson fails to specify what kinds of things are invariant and what kinds are not

Question 48

Visual Agnosias

Answer 48

Impairments in ability to interpret visual info
Can’t recognize objects by sight
Can sometimes recognize them by sound, touch, or smell
Problem lies in creating a percept from the proximal stimulus

Question 49

Apperceptive Agnosia

Answer 49

Can see contours or outlines of a drawing/object but have difficult time matching one object to another or categorizing them
Unable to form stable [pre semantic] representations of objects
Failure to interpolate missing contours or recognize objects from unusual angles
Some can’t name any objects
One case that couldn’t distinguish X from O
Associated with damage to the right hemisphere occipital lobe

Question 50

Associative Agnosia

Answer 50

Can form percept of object but cannot identify [cannot achieve a correct semantic description]…category specific
Can match objects/drawings and copy drawings, tend to be very slow at it
May become distracted by small details
Cannot readily name the objects they see or draw
Associated with bilateral damage to temporal region (both cerebral hemispheres)
Failed to identify objects presented visually (either confusing them with other objects or has not idea what it is)
Semantics intact given testing in another modality

Question 51

Category Specific Agnosia

Answer 51

Difficulty identifying items of a particular category, but ability to identify other types of objects is unaffected
Affected categories tend to include clusters of objects that are highly visually and semantically similar

Question 52

Prosopagnosia

Answer 52

Visual agnosia for faces
Can see details of faces, but cannot recognize a face as a coherent unit
Fail to recognize well known faces of friends/family or yourself
Damage to region in right hemisphere (potentially some left hemisphere involvement as well)
Normal people look at eyes to recognize faces
Proposagnosia people look at incorrect info when judging faces (e.g. mouth or nose)
May have intact object recognition abilities but can’t recognize family or well know people
Right fusiform gyrus (Fusiform face area [FFA])

Question 53

Unilateral Neglect (Hemineglect)

Answer 53

Ignore stimuli on the opposite side
Damage to parietal cortex
E.g. damage to right parietal cortex means they ignore stimuli on the left

Question 54

Covert (Unconscious) Face Recognition

Answer 54

There can still be evidence of covert (unconscious) face recognition
GSRs discriminate between familiar and unfamiliar faces
Can recognize people using voices, hair, posture, gait, etc.

Question 55

Capgras Syndrome

Answer 55

These patients are NOT prosopagnosic - face recognition abilities are intact
Fail to show a GSR response that discriminates between familiar and unfamiliar faces
They claim that their spouses are imposters E.g. insist that identical looking persons had taken the place of her family

Question 56

Capgras Syndrome Explanations

Answer 56

Results from an attempt to reconcile;
The fact that there is no (unconscious) feeling of familiarity (e.g. no GSR difference between familiar and unfamiliar faces)
The fact that they do agree the person LOOKS identical to someone they know (e.g. spouse)