Object perception - HLP1

Question 1

What are Gestalt’s grouping principals? (5)

Answer 1

• similarity
• proximity
• closure
• good continuation
• common fate

Question 2

What is figure-ground?

Answer 2

An area bound by closure is seen as a separate object. Contours are seen as belonging to one object at a time

Question 3

What is the purpose of Marr’s model of recognition?

Answer 3

proposing reasons for why Gestalt’s principals happen

Question 4

What are the 3 stages of Marr’s model of recognition? Briefly describe what happens in them

Answer 4

• primal sketch (2D representation of luminance)
• 2 1/2 D sketch (depth, orientation, shading, texture, motion binocular disparity - viewpoint dependent)
• 3D model (viewpoint invariant)

Question 5

What is the principal axis?

Answer 5

The biggest cylinder that makes up an object

Question 6

How do you recognise an object according to Marr? (3 stages)

Answer 6

• Identify the principal axis
• work through smaller and smaller cylinders
• match with 3D models in memory to the closest match

Question 7

What 2 things does Marr’s model of recognition predict?

Answer 7

• visibility of the principal axis is important
• different orientations are equally easy to recognise

Question 8

What is a problem with Marr’s model of recognition?

Answer 8

Many objects are hard to recognise if they are upside down or the principal axis is pointed towards the viewer

Question 9

What are the 4 stages in Biederman’s recognition by components?

Answer 9

• edge extraction (surface characteristics)
• detect arrangement of edges (don’t alter with view)
• segment object into components (parts)
• determine GEON type for each component

Question 10

What are GEONS?

Answer 10

Different shapes that are found in objects and their arrangement is used for object recognition

Question 11

What are 3 problems with Biederman’s model?

Answer 11

• doesn’t differentiate between objects in a class (e.g. 2 guinea pigs)
• doesn’t use surface pattern
• says recognition is viewpoint invariant but evidence says otherwise

Question 12

What brain regions are in the object processing pathways?

Answer 12

occipital cortex (v1) passes down to the anterior pole of the ventral temporal cortex, or to more dorsal regions to the posterior parietal cortex

Question 13

What region is necessary for the object discrimination task in monkeys?

Answer 13

Temporal lobe - ventral pathway (what)

Question 14

What region is necessary for the landmark discrimination task in monkeys?

Answer 14

parietal lobe - dorsal pathway (where)

Question 15

What damage causes object agnosia?

Answer 15

Ventral lateral temporal cortex

Question 16

What are the symptoms of object agnosia? How do they do in the object posting task?

Answer 16

inability to recognise objects (but can describe/draw from memory well)
Can’t match the hand well but can post the object well

Question 17

What happens in Titchener circles illusion?

Answer 17

people think the middle circles are different sizes but they are actually the same - influenced by the surrounding array
but they will reach with the correct grip

Question 18

What can you conclude from Titchener circles illusion?

Answer 18

Perception is affected by the illusion but grip aperture is not, so object analysis for action is separate from conscious perception of the object

Question 19

What are the symptoms of optic ataxia? (4)

Answer 19

• difficulty with visually guided reaching tasks
• difficulty reaching in the right direction
• difficulty positioning fingers correctly towards an object
• little relationship between grip aperture and object size

Question 20

Where in the brain is affected in optic ataxia?

Answer 20

parietal cortex - dorsal visual processing

Question 21

What is the role of the Lateral Occipital Cortex (LOC) in object recognition?

Answer 21

Identity representation
Location-tolerant object information and object-tolerant location information

Question 22

what did Hubel and Wiesel find in the visual cortex of the cat and monkey?

Answer 22

• simple cells that orient to a bar of light at a certain angle
• complex cells that respond to an oriented bar of light anywhere
• hypercomplex cells that respond to bars of light of the correct length

Question 23

What do each of these respond to: V1, V2, V4, posterior inferotemporal cortex, anterior inferotemporal cortex?

Answer 23

• v1 = edges
• v2 = contours
• v4 = colour and shape
• PIT = simple features
• AIT = specific elaborate features

Question 24

How does cell selectivity position itself in the inferotemporal cortex?

Answer 24

• columns that will like a specific thing, e.g. a star column
• posterior cells are orientation and size specific
• anterior cells are less sensitive to orientation and size

Question 25

What are the 3 layers in the hierarchical model of object recognition?

Answer 25

- V1 = simple stuff - V2 = more complex - PIT = most complex

Question 26

What are 5 positives of the hierarchical model of object recognition?

Answer 26

- anatomically and physiologically plausible - based on earlier hierarchical models - copes with viewpoint dependence/independence - incorporates theories of learning - familiarity = recognise from novel viewpoints - copes with multiple objects and in different contexts

Question 27

How would bottom-up processing work in object recognition?

Answer 27

start from low level features and move up to more detail until you reach the correct shape to match something in memory

Question 28

How would top-down processing work in object recognition?

Answer 28

start with the general context and find things that would fit there and match the best one

Question 29

How can top-down and bottom-up processing work together to have optimal object recognition? What models suggest this?

Answer 29

context can inhibit or excite certain things to make it easier for the bottom-up process to solve any ambiguity bidirectional processing models

Question 30

Which is more important: top-down or bottom-up processing in object recognition? Why?

Answer 30

Top-down as there are more descending connections than ascending

Question 31

What is the word superiority effect?

Answer 31

detecting a letter is easier when it is in a word

Question 32

At what age do babies start to show object permanence?

Answer 32

6 months

Question 33

Where in the brain activates when perceiving the similarity of objects?

Answer 33

ventral visual cortex

Question 34

What order is the hierarchy of how we group objects as similar in Cichy's study?

Answer 34

- colour - shape - background, free-arrangement

Question 35

What is a convolutional neural network?

Answer 35

AI pattern recognition for images, based on biological processes in the visual cortex of animals uses probabilities that something matches something else