Perception: vision

Question 1

Define sensation

Answer 1

The passive process of bringing information from the outside world into the body and the brain

Question 2

Define perception

Answer 2

The active process of selecting, organising, and interpreting the information brought to the brain by the senses

Question 3

Describe the organ brain structure association

Answer 3

Sense organ (eye) -> (arrows are electrical signals) receptor cells (rods and cones) –> nerve conduit (optic nerve) –> brain area (visual cortex)

Question 4

What are the two approaches to study perception?

Answer 4

Gestalt psychology and computational approach; feature representaiton

Question 5

What is gestalt psychology

Answer 5

Gestalt - german for form of shape
Paradigm which emerged in late 19th century
Concerned with identifying laws which govern visual perception

Question 6

What are gestalt laws

Answer 6

Explains how parts are arranged into forms and object and perceived as a whole

Question 7

What is an issue with gestalt psychology?

Answer 7

It is descriptive not mechanistic because a major focus of gestalt laws is describing the conditions that lead to grouping. Gestalt is less about understanding the mechanism underlying grouping

Question 8

What is the gestalt law of similarity?

Answer 8

Elements that look similar will be perceived as being part of the same form

Question 9

What is the gestalt law of proximity?

Answer 9

Elements that are close together will be perceived as belonging together

Question 10

What is the gestalt law of Good continuation?

Answer 10

We perceive lines as following a smooth course

Question 11

What is the gestalt law of closure?

Answer 11

A boundary isn’t necessary for us to perceive a shape. When small elements are arranged in groups, we tend to perceive them as larger figures. This can lead us to seeing illusory lines that do not exist.

Question 12

What is the gestalt law of Pragnanz (Similarity)?

Answer 12

We organise a scene according to its simplest (shortest) explanation

Question 13

What is the gestalt law of common fate?

Answer 13

Elements that move together tend to be grouped together

Question 14

What is the gestalt law of symmetry?

Answer 14

Elements that are symmetrical tend to be grouped together

Question 15

What is the gestalt law of parallelism?

Answer 15

Elements that are parallel tend to be grouped together

Question 16

What is feature representation in the visual pathway?

Answer 16

Eye-rods and cones-optic nerves-visual cortex

Question 17

What is the visual pathway?

Answer 17

1) retina
2) optic nerve
3) thalamus
4) primary visual striate cortext V1
5) High visual cortices V2 IT

Question 18

Describe feature representation in the optic nerve and thalamus

Answer 18

Receptive fields - features that neurons are most responsive too
- centre surround organisation
- light centre and dark surround or vice versa
- neurons responsive to dot like circular visual stimuli

Question 19

Describe feature representation in the primary visual cortex

Answer 19

• Classic studies by Hubel and Wiesel in 1950s investigating primary visual cortex
  Neurons in V1 respond to circular stimuli but are not very active
  Instead they are excited by line stimuli of specific orientation

Question 20

What is orientation important for

Answer 20

Edge detection

Question 21

What are receptive fields in V1 built up by

Answer 21

Combining receptive fields of neurons in the thalamus

Question 22

What are the two streams of visual processing?

Answer 22

The WHAT pathway and the WHERE pathway

Question 23

Describe the WHAT pathway

Answer 23

Identifies shape and objects, ventral to inferior temporal lobe , VENTRAL STREAM

Question 24

What is the WHERE pathway?

Answer 24

Motion, dorsal to superior parietal lobe, DORSAL STREAM

Question 25

Describe computational thinking

Answer 25

We reconstruct a visual scene by combining simpler elements, faithful reconstruction, built from visual inputs alone

Question 26

Describe how we think using gestalt psychology?

Answer 26

We combine elements in ways to gain a holistic understanding of a scene, simplified interpretation, built using assumptions and knowledge bout the world

Question 27

What is top down?

Answer 27

Background knowledge and expectations influence what is perceived. Expectation driven

Question 28

What is bottom up?

Answer 28

Processing the stimuli influences what is perceived - data driven

Question 29

Describe top down information

Answer 29

Context matters - our environment gives us clues when the stimulus is ambiguous. The context we perceive a stimulus in can cahnge our perception of it

Question 30

What are visual illusions a consequence of?

Answer 30

Bottom up vs top down processing

Question 31

How do we resolve ambiguities?

Answer 31

We need to decide which visual scene caused the image on the retina. Assumptions and cues are combined to make a best guess at what it is we're seeing. Cues; features of the image that give clues as to the nature of the stimulus (BU) Assumptions; expectations about what we will see or what different cues mean (TD)