Chapter 4 Recognizing Visual Objects Pg 117

Question 1

Object variety

Answer 1

the world contains an enormous variety of objects

*Flexibility, without restrictions

Question 2

Variable views

Answer 2

Different retinal images that can be projected by the same object or category of objects

Question 3

Representation

Answer 3

Pattern of neural activity in brain that contains information about a stimulus and give rises to subjective perceptual experience of that stimulus

Question 4

Recognition

Answer 4

Process of matching the representation of a stimulus to a representation store in long-term memory based on previous encounters with that stimulus or with similar stimuli

Question 5

Perceptual organization

Answer 5

1. Represent edges- abrupt, elongated changes in brightness and/or color
2. Represent uniform regions bounded by edges
3. Divide regions into figure and ground, and assign border ownership
4. Group together regions that have similar properties (e.g. color). Groups consisting of “figure” regions are represented as candidate objects; other groups of regions are represented as background.
5. Fill in missing edges and surfaces- that is, edges and surfaces that are partly occluded- to obtain more complete representations of candidate objects.

Question 6

Object recognition

Answer 6

Use higher-level processes to represent object fully enough to recognize them by matching their representations stored in memory

Question 7

Figure

Answer 7

Region of an image that is perceived as being part of an object

Question 8

Ground

Answer 8

Region of an image that is perceived as part of background

Question 9

Border ownership

Answer 9

Perception that an edge, or border, is “owned” by a particular region of retinal image

Question 10

Perceptual grouping

Answer 10

Process by which the visual system combines separate regions of the retinal image that “go together” based on similar properties

Question 11

Perceptual interpolation

Answer 11

Process by which the visual system fills in hidden edges and surfaces in order to represent the entirely of a partially visible object.

Question 12

Edge extraction

Answer 12

visual system determines the location, orientation, and curvature of edges in retinal image, based on patterns of responses from neurons in area V1, V2, V4-> “What” pathway

Question 13

Uniform connectedness

Answer 13

Characteristic of regions of the retinal image that have approximately uniform properties.

Question 14

Depth

Answer 14

Front (Figure)

Back (ground)

Question 15

Surrounding

Answer 15

surround region (owning borders, figure)

Question 16

Symmetry

Answer 16

Region with symmetrical borders ->figure

Question 17

Convexity

Answer 17

Convex borders, outward-bulging region(figures)

Concave, inward-going region (background)

Question 18

Meaningfulness

Answer 18

Figure-ground organization precedes object recognition

• Regions perceived as figure are meaningful- they correspond to object shapes store in memory
• Recognizes object shapes prior to assignment of border ownership and determination of figure-ground organization

Question 19

Simplicity

Answer 19

Number and placement of shapes composing image

Question 20

Proximity

Answer 20

Elements that are close together group more easily than elements that are far apart
*Things that are near to each other are grouped together

Question 21

Similarity

Answer 21

Similar elements tend to group together

*Similar things are grouped together

Question 22

Common motion (Common fate)

Answer 22

Elements that move in unison are likely to be perceptually grouped
*Things moving in same direction are grouped together

Question 23

Symmetry and Parallelism

Answer 23

symmetrical/parallel tend to group together

Question 24

Good continuation

Answer 24

two edges that would meet if extended are perceived as single edge that has been partially occluded, like the top and bottom edges of horizontal bar.

• Edges that are aligned, or follow the smoothest or straightest path, are seen as part of the same contours.
• Points that, when connected, result in contours. These contours follow the smoothest path.

Question 25

Synchronized neural oscillations

Answer 25

Those neurons could indicate that the regions belong together by synchronizing their oscillations- by producing clumps of spikes at the same time *Similarity of orientation, good continuation, common motion

Question 26

Edge completion

Answer 26

The perception of a partially hidden edge as complete; one of the operations involved in perceptual interpolation

Question 27

Illusory contours

Answer 27

nonexistent but perceptually real edges perceived as a result of edge completion *Result of an explicit perceptual representation quite early in the visual stream

Question 28

Surface completion

Answer 28

The perception of a partially hidden surface as complete; one of the operations involved in perceptual interpolation

Question 29

Heuristics

Answer 29

In perceptual organization, rules of thumb based on evolved principles and on knowledge of physical regularities *It's always possible to reject he most likely interpretations of how a scene is organized perceptually, in favor of a less likely interpretation based, perhaps on subtle clues

Question 30

Perceptual inference

Answer 30

In vision, the interpretation of a retinal image using heuristics *Using heuristics in a way, to guide the interpretation of a retinal image based on knowledge of physical regularities in the world

Question 31

Shape representation in V4

Answer 31

Edges, preferred orientation Shapes are represented in V4 by the combined activity of all the neurons responding to the contour fragments making up the shape Population code representing entire shape

Question 32

Inferotemporal (IT) cortex

Answer 32

increase receptive fields than V4 * Almost entire retinal image * More complex * Specific combinations of contour fragments * Structural description

Question 33

Grandmother cell

Answer 33

A neuron that responds to a particular object at a conceptual level, firing in response to the object itself, a photo of it, its printed name, and so on

Question 34

Throughout the visual hierarchy

Answer 34

``` V1+V2= detailed info about locations of edges of slots and handle of toaster V4= info about curvature and orientation of toaster's various contours IT= more complex aspects of toaster's shape, highest-level neurons, invariant representation of the concept "toaster" ```

Question 35

Modular coding

Answer 35

Representing of an object by a module, a region of the brain that is specialized for representing a particular category of objects * Certain categories of objects can strongly activate specific brain regions * Fusiform face area (FFA): faces * Parahippocampal place area (PPA): buildings, outdoor scenes * Exrastriate body area: human and animal bodies

Question 36

Distributed coding

Answer 36

Representation of objects by patterns of activity across many regions of the brain

Question 37

Visual agnosia

Answer 37

Impairment in object recognition

Question 38

Prosopagnosia

Answer 38

A type of visual agnosia in which the person is unable to recognize faces, with little or no loss of ability to recognize other types of objects

Question 39

Topographic agnosia

Answer 39

A type of visual agnosia in which the person is unable o recognize spatial layouts such as buildings, streets, landscapes, and so on

Question 40

Top-down information

Answer 40

Flow of information from higher regions to lower regions * Goals, attentions, knowledge * Visual system first creates a representation of general, overall layout of the scene and tries to match that with representations of the general layout of specific with representations of the general layout of specific categories of scene stored in memory

Question 41

Bayesian approach

Answer 41

In object recognition, the use of mathematical probabilities to describe the process of perceptual inference * The visual system unconsciously combines two probabilities in order to infer what type of scene produced the currently experienced retinal image (1) Prior probability of all possible scenes and (2) for each possible scene, the probability that it produced the current retinal image

Question 42

Feature-Based Approach

Answer 42

* Identifying the most prominent anatomical features of a face and the spatial relations among them * Differences in pose person's expression, lighting, shadow, distance from face to camera * Statistical method for finding the best match

Question 43

Holistic Approach

Answer 43

Matching an image of a test face as a whole with images of known face as a whole with images of known faces in database * Eigenfaces: face images generated from a set of digital images of human faces taken under the same lightening conditions, normalized to line up the eyes and mouths, and rendered with the same spatial resolution * Start with average face and add a weighted sum of the other eigenfaces

Question 44

Hybrid Approach

Answer 44

Combines the best aspects of the holistic and feature-based approaches *Eigenfaces were supplemented by eigen-feature representations

Question 45

Image clutter

Answer 45

a characteristic of visual scenes in which many objects are scattered in 3-D space, with partial occlusion of various parts of objects by other objects

Question 46

Photoreceptors

Answer 46

point-by-point "pixels", separate arrays for each of 4 photoreceptor types

Question 47

Retinal midget-ganglion cells

Answer 47

Small, edge-enhancing receptive fields, high spatial resolution

Question 48

Early cortical cells

Answer 48

Respond to oriented edges and lines, size selectivity, retinotopic maps

Question 49

How does the brain construct representations of objects?

Answer 49

* Using local features to guide global interpretations - e.g., fake spiral (Frasier) illusion, impossible figures - more inductive, bottom-up * Using global interpretation to guide local interpretations - e.g. Necker cube, reversible figures - more deductive, top-down

Question 50

Figure-ground segregation

Answer 50

Determining what part of environment is the figure so that it "stands out" from the background.

Question 51

Border assignment

Answer 51

to what region does a particular edge (border) belong

Question 52

Figure-ground organization

Answer 52

* The figure is more "thinglike" and more memorable than ground. * The figure is seen in front of the ground. * The contour separating figure from ground belongs to the figure (border ownership)

Question 53

Some specific factors that can determine which region is figure

Answer 53

* Depth: region in front of another * Regions surrounded by other(s) * Regions that are symmetrical * Regions that have convex (bulgy) shapes * Regions that have meaningful shapes * Regions located in the lower part of scene * Regions that are small * Regions oriented vertically and/or horizontally

Question 54

Structuralist Approach

Answer 54

* Wilhelm Wundt * States that perceptions are created by combining elements called sensations * Popular in mid to late 19th century * Wundt studied conscious experience by examining its structure or component parts (sensations, feelings) using individuals who were trained in introspection. This "school of psychology" became known as structuralism. * Could not explain apparent motion, illusory contours,

Question 55

Kanizsa Triangle

Answer 55

* First described by Gaetano Kanizsa in 1955 * 2 equilateral triangles appear present except non are actually drawn * The "inside" of the top triangle appears to be a brighter shade of white than the rest.

Question 56

Gestalt psychology

Answer 56

It seems that the visual system "looks" for regularity, patterns, and structure in particular ways because they are generally useful (accurate, efficient) in constructing perceptions of the world.

Question 57

Gestalt approach

Answer 57

* The whole is different than the sum of its parts. * Perception is not built up from sensations but is a result of perceptual organization. * Specific principles or laws of perception - Describe how elements in a scene tend to group together. - Better thought of as heuristics, "best-guess rules", rather than fixed laws or algorithms * Pragnanz: every stimulus is seen as simply as possible - Also called the "law of good figure" - The central law of Gestalt psychology

Question 58

Common region

Answer 58

* Gestalt Principles of Perceptual Organization | * Elements in the same region tend to be grouped together

Question 59

Connectedness

Answer 59

* Gestalt Principles of Perceptual Organization | * Connected regions of visual are perceived as single unit

Question 60

Synchrony

Answer 60

* Gestalt Principles of Perceptual Organization | * Elements occurring or disappearing at the same time are seen as belonging together

Question 61

Theory of unconscious inference

Answer 61

* Hermann von Helmholtz * Why stimuli are interpreted the way they are and can be interpreted in more than one way * Perceptions are the result of unconscious assumptions about the environment * Likelihood principle: objects are perceived based on what is most likely to have caused the pattern * Opposed to Structuralist views, anticipated aspects of Gestalt views

Question 62

Bayesian approaches

Answer 62

Modern researchers | *take assumed prior probabilities into account, to model perceptual inference.

Question 63

Physical regularities

Answer 63

Regularly occurring physical properties * Border ownership * Figure-ground organization * Perceptual grouping

Question 64

Tilt and size aftereffects

Answer 64

* tuned mechanisms: neurons responsive to particular narrow ranges of orientation or size * Represents size and orientation by the pattern of activity * Selective adaptation desensitizes some of these tuned neurons/mechanisms