W10: Perceptional Organisation & Attention

Question 1

Define figure ground segmentation with an example of bistable percept

Answer 1

Process of segmenting object from background in a bistable percept where image is ambiguous leading to switching between 2 percepts

e.g. Rubin Vase - 2 white faces or a black Vase

Question 2

What are the 6 Gestalt Principles of Grouping?

Answer 2

1. Proximity: close objects group together
2. Similarity: similar objects group together
3. Common Fate: objects moving together group together
4. Good Continuation: smooth continuity over abrupt changes
5. Closure: closed figure grouping preferred over open
6. Relative size, surround, orientation, symmetry

Question 3

Describe illusory contours with an example

Answer 3

Invisible contours detected by V2 e.g. Ehrenstein illusion

Question 4

Name 5 perceptual constancies

Answer 4

1. Colour: perceive surface reflectance
2. Lightness: brightness appears same under different intensities
3. Spatial: world persists as stable spatial representation despite eye movements
4. Shape: perceive correct shape in any angle/view
5. Size: perceive correct size despite changing distance

Question 5

Explain the moon illusion

Answer 5

Moon appears larger when close to horizon so also appears larger as perceived distance of sky is incorrect.

Sky appears closer straight up than at horizon so perceived size of moon changes. (Size constancy)

Question 6

How do adaptations affect the visual system?

Answer 6

motion aftereffect temporarily makes moving stimulus to appear as moving in opposite direction

Question 7

Describe the McCollough Effect

Answer 7

Long lasting pattern contingent colour aftereffect after looking at a pair of colour-orientation patterns for 5 mins. After adaptation, achromatic patterns appear coloured. Demonstrates ability to learn associations and early interaction between visual features

Question 8

Explain visual attention

Answer 8

Ability to engage in flexible strategies for processing differing aspects of the visual field in a rapid phase across the scene and a 2nd phase to guide search

Question 9

Explain different types of search

Answer 9

Visual:
Parallel: pre-attentive (distributed, different parts of scene)
Serial: attentive (sequence of attentional fixations) time taken affected by distractors

Question 10

Explain the binding problem

Answer 10

process of conjoining different scene features into single perceptual entity - unknown how cortex does this

Question 11

Explain Feature Integration Theory

Answer 11

based on visual search; pre-attentive parallel processing creates feature maps
apply attentional spotlight to master map of object locations which binds visual features at selected location

Question 12

What is the McGurk effect?

Answer 12

multi-modal illusion where vision and hearing interact in sensory fusion
sound heard is based off mouth movement rather than actual sound

Question 13

Describe synesthesia and 2 example forms

Answer 13

Synesthesia: stimulation of 1 sensory/cognitive pathway leads to involuntary experiences in a 2nd pathway

Graphene-Colour: associates colour with letters/numbers
Spatial Sequence/Number Form: associates spatial locations with number (sequences)