Task 5: Mechanisms of middle and high-level vision

Question 1

Goal of middle vision

Answer 1

organise elements of visual scene into groups

Question 2

Perceptual organisation

Answer 2

process by which elements in environment become perceptually grouped to create our perception of obejcts

Question 3

Components of perceptual organization

Answer 3

1. Grouping (putting together into units)

2. Segregation (separating one area from another)

Question 4

Structuralism

Answer 4

• accumulated parts create the whole

- opponent to Gestalt approach

Question 5

Gestalt approach

Answer 5

• an objects is a whole independent of the parts

- approach based on heuristics and not laws

Question 6

Demonstrations against adding up sensations (structuralism)

Answer 6

• apparent movement

- illusory contours

Question 7

Gestalt organizing principles about perceptual grouping

Answer 7

1. Law of Pragnanz = structure is as simple as possible
2. Law of Similarity = similar things appear to be grouped together (colour, shape, size and orientation)
3. Law of good continuation = objects partially covered by other objects are seen as continuing behind the covering object
4. Law of Proximity = things that are near each other
   - principle of common region (overpowers proximity)
   - principle of uniform connectedness (connected regions)
   - principle of common fate (moving in the same direction)

Question 8

Factors that determine perceptual segregation of figure and ground

Answer 8

• border ownership: even when figure and ground share contour, the border is associated with the figure
• we perceive an object as figure because of its meaningfulness, symmetry and region (lower region is better)
• the ground lack shape

Question 9

Reversible figure-ground

Answer 9

patterns that can be perceived differently in the context

Question 10

Relative motion

Answer 10

perceiving objects because they move

Question 11

Gist of a scene

Answer 11

meaning of a scene that can be recognised within a fraction of a second
- is perceived first, followed by perception of details

Question 12

Inference in perception

Answer 12

• knowledge of physical and semantic regularities
• some perceptions are the result of unconscious assumptions about the environment
• likelihood principle

Question 13

Bayesian inference

Answer 13

• perception is combination of current stimulus and knowledge about the conditions of the world
• prior probability
• consistency of hypothesis

Question 14

What are the different visual areas in the temporal lobe responsible for low, middle and high - level vision?

Answer 14

Low-level vision = V1 = Area 17 = Striate cortex
- lines and edges

Middle-level vision = V2 = Area 18

• border ownership
• real and illusory contours
• combines lines to form objects

High-level vision = V4
- complex attributes

Question 15

Naive template theory

Answer 15

• is inaccurate because too many templates would be needed

- matching neural representation with a stored representation of the same shape in the brain

Question 16

Solution for the naive template theory

Answer 16

structural description = objects perceived as relationship between parts, therefore we would keep in memory only one representation (recognise Jennifer Anniston with glasses and without)

Question 17

Biederman’s Model of Recognition-by-Components theory

Answer 17

• objects are recognised by identities and relationships of their component parts
  = usually recognise objects by the use of geons

Question 18

Geon

Answer 18

• parts of which the perceptual objects is built
• easy and quick to recognise, regardless of orientation in space
• viewpoint invariant

Question 19

Viewpoint invariance

Answer 19

representations of an object don’t change when observer’s viewpoint changes

Question 20

Template descriptions

Answer 20

2D memory representations from different viewpoints

Question 21

Another way by which objects are recognised is by

Answer 21

entry-level category (label)

=> subordinate (specific) or superordinate (broader) level

Question 22

Illusory contours evoke response in

Answer 22

area 18 of the visual cortex (V2)

Question 23

Area 17 is

Answer 23

unable to see contours

Question 24

Other factors that pay a role in the formation of contours are

Answer 24

corners and line ends

Question 25

Illusory contours are generated by

Answer 25

the amount of contrast at luminance borders

Question 26

Experiment I with the Kanisza square concluded that

Answer 26

children of 3-4 months are able to extract subjective contours

Question 27

Visual word form area

Answer 27

activated when we read

Question 28

Pure alexia

Answer 28

• impariment in VWFA
• inability to recognise a single word, faces, objects, digits and numerals
• ability to speak and even write

Question 29

We are able to read because

Answer 29

of a preexisting circuit that links left ventral visual pathway to left-hemispheric language areas

Question 30

Left hemisphere lateralisation

Answer 30

of VWFA, the same as spoken language

Question 31

Neurons in visual pathway respond to

Answer 31

simple shapes => they signal properties that tent to be viewpoint invariant

Question 32

Acquisition of reading induces

Answer 32

reorganisation of ventral visual pathway (features for letter recognition are incompatible with those for faces) => one area pushes the other away, towards the right hemisphere