Object recognition

Question 1

Define perception

Answer 1

Our ability to extract meaning from sensory input

Question 2

What are the four types of receptors?

Answer 2

Thermoreceptors, photoreceptors, chemical receptors, mechanical cells

Question 3

What does the phrase “perception is a constructive process” mean?

Answer 3

The cognitive system constructs perception… it is not a passive process, it is a lot top-down and then interacts with the information coming in and “corrects” mistakes (e.g. blind spot - brain fills in, constructs perception by visual system)

Question 4

Is our vision accurate?

Answer 4

No… our field of view is mostly illusionary

Question 5

How many visual fields is each eye split into?

Answer 5

Two

Question 6

Which hemisphere of the brain does each visual field transmit information to?

Answer 6

The right visual field in each eye processes information in the left hemisphere of the brain and the left visual field in each eye processes information in the right hemisphere of the brain

Question 7

What are the three stages in the three stage model of object recognition?

Answer 7

1. Local features (edge detection/contrast)
2. Shape representation (Gestalt principles/feature integration)
3. Object representation (stored representations/knowledge)

Question 8

What are the dorsal and ventral pathways in the brain?

Answer 8

Dorsal - where objects are in space
Ventral - Object recognition

Question 9

What happens are you go further down the dorsal and ventral pathways?

Answer 9

Object recognition gets more complicated - neutrons fire more and more complex stimuli (V1 identifies simple features like corners, further on = more complex intersection, facial recognition relies on processes much further down the ventral pathway)

Question 10

Describe the monkey experiment where their retinas where examined

Answer 10

Monkey anaesthetised, eyes open, injected with radioactive glucose, stare at stimulus, kill monkey, take retina out, lay out flat, stimuli reflected on retina

Question 11

Where in the brain is the visual cortex?

Answer 11

In the occipital lobe

Question 12

The Gestalt principle states that the whole visual percept is…

Answer 12

…more than the sum of its parts

Question 13

Our perceptual system constantly tries to impose what on its input?

Answer 13

Organisation

Question 14

Define monocular rivalry

Answer 14

When completely different images are presented to each eye our brain doesn’t know which one to choose (bistable stimuli)

Question 15

What are the four things we make assumptions about?

Answer 15

Proximity, similarity, good continuation, closure

Question 16

In terms of shape perception, “bottom-up” processes produce what?

Answer 16

Primal sketches

Question 17

In terms of shape perception, “top-down” processes produce what?

Answer 17

Group collections of primitives together into lines, curves, larger blobs, groups and small patches to produce symbolic primitives

Question 18

What is a template?

Answer 18

An internal representation

Question 19

Summarise the key concepts of feature analysis

Answer 19

1. Assumes low level features are analysed first
2. Perceptual system searches for simple but characteristic features of an object
3. Cells in brain fire when see certain angled stimuli
4. Recognition by components

Question 20

What is a geon?

Answer 20

An arrangement of simple 3D shapes that can represent a specific view of an object. Viewpoint invariant - easily recoverable from a 2D retinal image

Question 21

What are two invariant properties?

Answer 21

Cotermination and parallelism

Question 22

Object recognition is impaired when geons are made non-recoverable by removing what…

Answer 22

Termination points