Chapter 5: Perceiving Objects + Scenes

Question 1

What are 5 reasons why it would be difficult to design a machine meant to perceive?

Answer 1

1. Shading and colouring are difficult to interpret (cannot differentiate shadow from pigment)
2. Objects can be hidden or blurred
3. Occlusions are common in the environment
4. Inverse Projection Problem: a specific image on the retina can be caused by an infinite number of objects
5. Viewpoint Invarience: the ability to recognize an object regardless of the viewpoint

Question 2

Define Perceptual Organization?

Answer 2

Process where elements in the environment become groups to create our perception of objects

Question 3

What are the 2 theories regarding perceptual organization?

Answer 3

1. Structuralism: perception is created by combining many tiny sensations
2. Gestalt Psychology: the whole is greater than the sum of its parts

Question 4

What are 2 pieces of evidence that support the theory of Gestalt Psychology?

Answer 4

1. Apparent Movement (Wertheimer): illusionary phenomenon where if 2 stimuli are flashed close to one another with 50ms in between, movement is perceived from the first stimulus to second
   - Cannot be explained by elementary perception (no movement)
   - Cannot be explained by structuralism theory
2. Illusory Contours: illusionary contours that represent edges
   (Check notes for drawing)

Question 5

What are the 5 original Gestalt Principles of Organization?

Answer 5

1. Pragnaz (Law of simplicity): every pattern is seen as the simplest structure possible
2. Similarity: similar things appear grouped
3. Good Continuation: lines appear to follow smoothest, continuous path
4. Proximity: objects that are near appear grouped
5. Common Fate: elements pointed in the same direction are grouped

Question 6

What are the 3 newer Gestalt Principles of Organization?

Answer 6

6. Common Region: elements within the same region are grouped
7. Uniform Connectedness: a connected region (by colour, texture, motion) appears as a single unit
8. Synchrony: visual events occurring at the same time appear grouped

Question 7

Define Figure-Ground Segregation

Answer 7

Perceiving figures as separate from the background

Question 8

What are the 5 features of figures and grounds that allow perceptual segregation of the two?

Answer 8

1. Figures are “thing-like” and memorable
2. Figures are seen in front of the ground
3. Grounds are “uniformed” and extends behind the figure
4. The contour separating figure from ground belongs to the figure
5. In the case of reversible figures, it is not possible to see both simultaneously

Question 9

What are the 4 factors that influence Figure-Ground Segregation?

Answer 9

1. Location: bottom right likelier to be seen as figure
2. Convexity: higher convexity likelier to be seen as figure
3. Size: plus figure/smaller area is seen as figure
4. Meaning: meaningful region is seen as figure

(Gestalt psychologists did not believe in the influence of experience/exposure)

Question 10

What is the difference between a scene and objects in a scene?

Answer 10

A scene is acted WITHIN, an object is acted UPON

Question 11

Define Gist

Answer 11

A general scene description

Question 12

What did Potter discover about Gists? Using what experiment?

Answer 12

A target photo/description was provided, and observers had to decide if the target photo was showed when provided 16 photos a 250ms each

• Result: 90% accuracy
• Finding: it only takes 1/4secs to perceive gists

Question 13

What did Fei-Fei discover about gists? Using what experiment?

Answer 13

Observers were asked to write descriptions of photos that were shown for a range of 20ms-500ms

• Result: descriptions were more detailed when given more time to view a photo
• Finding: an overall gist is perceived first, followed by details

Question 14

What is Masking (used by Fei-Fei)?

Answer 14

Presenting unrelated stimulus after presenting the test stimulus

Question 15

What are Global Features?

Answer 15

Features that help get the gist of a scene rapidly

Question 16

What are the 5 Global Features?

Answer 16

1. Degree of naturalness
2. Degrees of openness
3. Degree of roughness
4. Degree of expansion
5. Colour

Question 17

Why did the visual system evolve?

Answer 17

To take advantage of properties in the environment

Question 18

Define Regularities

Answer 18

Characteristics that are correlated with specific objects or locations

Question 19

What is the Oblique Effect?

Answer 19

People perceive vertical and horizontal contours more easily, probably because there are more horizontal and vertical lines in our environment (city)

Question 20

Define Semantic Regularities

Answer 20

Characteristics associated with the function of scenes

Question 21

What was Hollingworth’s experiment regarding semantic regularities?

Answer 21

Observers were asked where a target object was or where they would expect it to be, after being presented with a scene (with or without the target), then the target followed by a blank screen
- Result: both groups accurately predicted

Question 22

What was Palmier’s experiment regarding semantic regularities?

Answer 22

A scene and target image are flashed, then observers were asked to identify the object in the target picture

• Result: when the target fit with context, 80% accuracy
• Result: when the target felt misplaced, 40% accuracy

Question 23

Define Unconscious Inference

Answer 23

Our perceptions are results of unconscious assumptions about the environment

Question 24

Define Heuristic

Answer 24

Rule of thumb that provide a best-guess solution to a problem
(Gestalt Principles are heuristics)

Question 25

What is Contextual Modulation?

Answer 25

Idea that stimuli utside the receptive field can affect neural firing - Neurons in the visual cortex respond the Gestalt Principles (areaV1) - Likely due to feedback from higher areas

Question 26

What is the Grill-Spector experiment?

Answer 26

FFA was monitored with fMRIs, observers were asked to indicated what they saw when presented either Harrison Ford's face, a stranger's face, or texture - Result: FFA activation was greatest when Ford's face was correctly identified, least when there was no identification of a face

Question 27

What was Sheinburg+Logotheris' experiment (using binocular rivalry)?

Answer 27

Monkeys were trained to pull levers for sunburst and for butterflies, while neurons in the IT cortex were monitored for response - Result: vigorous firing for butterflies only

Question 28

What is Binocular Rivalry?

Answer 28

A technique used during experiments where 2 separate images are shown to different eyes at the same time; each image can only be seen part of the time

Question 29

What was Tong's experiment?

Answer 29

Binocular rivalry was used when showing participants a house and a face - Result: increased activity in parahippocampal place area (PPA) for the house - Result: increased activity in FFA for the face

Question 30

What does the Amygdala respond to?

Answer 30

Emotional aspects of faces

Question 31

What does the Superior Temporal Sulcus (STS) respond to?

Answer 31

Where a person is looking and to mouth movements

Question 32

What does the Frontal Cortex (FC) respond to?

Answer 32

While evaluating facial attractiveness

Question 33

Faces elicit fastest eye movements and are processed fastest. When are these heightened?

Answer 33

- When in the right shading, rather inverted colours | - When it is a familiar face

Question 34

What is the Preferential Looking Effect?

Answer 34

Preference for familiar faces Experiment: babies presented 2 identical displays with stimuli displayed, while the amount of time watching each of the screens is recorded