Perception

Question 1

On-off Receptive Field

Answer 1

Ganglion: Light at center on small region, increase rate of firing; around region, decrease rate.

Question 2

Off-on Receptive Field

Answer 2

Ganglion: Light at center on region decreases rate of firing; light in surrounding increases rate

Question 3

Edge/bar detection

Answer 3

Multiple On/Off ganglion cells in LGN make pattern that stimulates detector in visual cortex

Question 4

Goal of Perception? Why difficult?

Answer 4

To infer structure of external world from information available to senses.
Problem: information is variable and ambiguous

Question 5

Information: ambiguous? variable?

Answer 5

1) Different things can appear the same (obstruction or uncertainty of position)
2) Same thing can look different (viewed from different angles, farther, nearer)

Question 6

Monocular depth cues

Answer 6

interposition, linear perspective, texture gradient, shading and contours, atmospheric blur, motionparallax, relative height, relative size

Question 7

Binocular depth cues

Answer 7

retinal disparity (gives rise to stereoillusions, apparent size illusion)

Question 8

Solution to perception problem

Answer 8

Perceptual system makes reasonable guesses based on reliable cues. Ignores unreliable cues and give rise to perceptual constancies

Question 9

How does stereogram generate perception of depth?

Answer 9

Images with slight disparity fused. Visual system assumes disparity due to retina and stereopsis, perceive as 3D

Question 10

Does apparent size track retinal size or actual size?

Answer 10

Actual size. Demonstrated by apparent size illusion, where farther person is moved to same plane as closer person (appears smaller as opposed to farther away)

Question 11

Perceptual Constancies

Answer 11

Objects are perceived as actual size rather than retinal size (for size constancy, person is not actually smaller, just farther away). Visual system ignores unreliable cues to produce perceptual constancies.

Question 12

Low-level vision

Answer 12

Edge detection
Color
Spatial localization

Question 13

Mid-level vision

Answer 13

Object features
Fig/ground segmentation
Perceptual organization

Question 14

High-level vision

Answer 14

Object recognition
Face recognition
Scenerecognition

Question 15

What are invariants? Importance?

Answer 15

Invariants are edges that are distinguishable regardless of orientation of depth. Helps classification despite drastic variations in the object’s silhouette, specific contours, and occlusion of large regions of the object.

Question 16

Evidence that feature relations used in recognition

Answer 16

Biedelman(1987). Experiment testing RT for original images, missing lines, and missing vertices. RT increases from former to latter.

Question 17

Template Matching Theory

Answer 17

Objects identified by matching percepts with stored representations (“templates”). Given object can have multiple templates and alignment must occur before matching. No need to define features!
Problem: Templates can be mismatched, wrong size, wrong part of retina, wrong orientation etc.

Question 18

Feature Analysis Theory

Answer 18

Stimuli are combination of elemental features
Pros: features are simple, less difficulty matching; can specify important features that “pop out”; reduces complexity and overload of templates
Con: Relationships between features not represented;

Question 19

Structural description/recognition-by-components Theory

Answer 19

Recognize object as configuration of simpler components/subobjects (“geons”), classify subobjects, recognize pattern.

Question 20

Object-centered Representation

Answer 20

Perception more dependent on object and features. Structural description theories

Question 21

Viewer-centered Representation

Answer 21

Perception more dependent on observer and limiations. Template matching theories

Question 22

Face recognition evidence

Answer 22

Fusiform gyrus respond to faces, face cells in monkeys, damage causes selective difficulty in recognizing faces (prosopagnosia)

Question 23

Inversion effects

Answer 23

Better at recognizing upright faces, worse when upside down (Margaret Tatcher Illusion). Not true for other objects

Question 24

Greebles, Tarr’s Experiment

Answer 24

Can be trained to recognize other complex objects and activate same fusiform, not just face processing. Also shows inversion effect

Question 25

Top-Down Processing

Answer 25

Occurs when context guides perception; higher level knowledge contributes to interpretation of lower-level perception

Question 26

Bottom-Up Processing

Answer 26

Stimulus provides information by itself, regardless of context

Question 27

Word Superiority Effect

Answer 27

When presented with ambiguous stimuli, more accurate when identifying word than letters alone. Word context supplements lone feature information

Question 28

Gestalt Principles of Grouping

Answer 28

Objects tend to be organized into units according to set of principles. Proximity, good continuation, common region, similarity, common fate, closure