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Action & Perception > 3. Object Recognition > Flashcards

3. Object Recognition Flashcards

1
Q

Biederman’s recognition-by-components theory proposes that objects consist of primitives known as what?

A

geons

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2
Q

What series of stages are involved in object recognition?

A
  1. percieve/ see object
  2. structural description of the object
  3. semantic representation
  4. name representation
  5. name
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3
Q

Viewpoint invariant mechanisms of object recognition are usually involved when a task involves what?

A

a

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4
Q

Which disorder involves problems with object recognition that result from deficits in perceptual processing?

A

Apperceptive Agnosia

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5
Q

In which disorder can patients copy objects, even though they don’t recognise them?

A

associative agnosia

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6
Q

Differences between face and object recognition?

A
  • Object recognition tend to involve between category discriminations
  • face recognition always to involve with-category discriminations
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7
Q

What are the challenges with intra-class variation for object recognition?

A
  • We can still recognise something (e.g. chair) even though the features and appearance vary vastly.
  • Recognition when only part of an object is visible.
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8
Q

What are the challenges with viewpoint variation for object recognition?

A
  • Is more difficult to make discrimination if it is the same person across different view points
  • Even though we might not be able to tell if it is the same person we can still tell that it is a person.
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9
Q

What are the 4 theories of 2D pattern recognition?

A
  1. Template theories
  2. Prototype theories
  3. Feature theories
  4. Structural descriptions
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10
Q

Describe the Template theory of 2D pattern Recognition.

A
  • We have a mini copy or template in LTM of all known patterns.
  • Compare stimuli to templates in memory for one with greatest overlap until a match is found
  • Recognise an object when there is the most overlap from templates form LTM
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11
Q

What are the problems with the Template theory of 2D pattern Recognition?

A
  • Problem of imperfect matches
    ○ Cannot account for the flexibility of pattern recognition system
  • Cannot account for our flexibility in ability to recognize items.
  • Comparison requires identical orientation, size, position of template to stimuli
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12
Q

Describe the Prototype theory of 2D pattern Recognition.

A
  • Modification of template matching (flexible templates) = one average template stored in memory.
  • Possesses the average of each individual characteristic
  • No match is perfect; a criterion for matching is needed
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13
Q

What is the evidence for the Prototype theory of 2D pattern Recognition?

A 
Franks & Bransford (1971)
	○ Presented objects based on prototypes
	○ Prototype not shown
	○ Yet participants are confident they had seen prototype
	○ Suggests existence of prototypes
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14
Q

What are the problems with the Prototype theory of 2D pattern Recognition?

A

○ Old literature so not too reliable (i.e. Franks & Bransford, 1971)
○ Consistent with prototype theory but doesn’t discount other possibilities

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15
Q

Describe the Feature theory of 2D pattern Recognition.

A
  • Pattern consists of a set of features or attributes.
  • A = 2 straight lines & connecting cross bar.
  • But also need to know relationship between features as well as the features themselves.
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16
Q

Describe the Structural descriptions theory of 2D pattern Recognition.

A

“describes the nature of the components of a configuration and the structural arrangement of these parts” (Bruce & Green, 1990)

17
Q

What are the problems with the Structural descriptions theory of 2D pattern Recognition?

A
  • Need to know relationship between these features as well
18
Q

Describe the process of 3D object recognition.

A
  1. interpret input to visual system as coherent structures, segregated from one another & from background. (Early image processing)
  2. create structural description of the object
  3. which can then be matched to the descriptions of visual objects stored in memory.
19
Q

What did Marr & Nishihara (1978) propose?

A

○ Can break all objects down into a series object cylinders (feature/ components)
○ Need to work out the relationship between cylinders. This creates your structural description of that object.
○ expressed structural relations by a hierarchical organisation of cylinders.

20
Q

What did Biederman (1987; 1989) propose?

A
  • Recognition-by-components theory: Objects composed of basic shapes

○ GEONS = ‘geometrical ions’.
○ approximately 36 different volumetric shapes
○ Viewpoint invariant theory

21
Q

How can geons vary?

A
  • Relative size
  • Verticality
  • Centring
  • Relative size of surfaces at join
22
Q

What are the ‘non-accidental’ properties of geons?

A

○ Curvature - points on a curve
○ Parallel - set of points in parallel
○ Co-termination - edges terminating in a common point
○ Symmetry - versus asymmetry
○ Co-linearity - points in a straight line

23
Q

What is the object recognition process that we go through according to Biederman (1987)?

A
  1. Edge extraction
  2. Detection of Non-accidental properties
    or
  3. parsing of regions of concavity
  4. Determination of components
  5. matching of components to object representations
24
Q

How did Biederman (1987, 1989) evidence his theory?

A
  • deleted edges of line drawings at points where easily reinstated or difficult to determine.
  • Deletion of component affects matching stage
  • Midsegment deletion makes it more difficult to determine components.
  • Midsegment deletion led to less errors than component deletion.
25
Q

What is the support for Biederman’s geon theory?

A
  • Vogels, Biederman, Bar & Lorincz (2001) found some cortical neurons in monkeys sensitive (responded more) to geons.
26
Q

What are the disadvantages of Biederman’s theory?

A
  • Structure is not always key to recognition: Peach vs. Nectarine
    ○ Colour is important here not just geons
    ○ Face discrimination: texture, colour are key for identification
  • Simplifies the contribution of viewpoint-dependence
27
Q

Describe the Viewpoint Dependent Theory.

A
  • Assume changes in viewpoint reduce the speed and / or accuracy of object recognition.
    ○ Suggest viewpoint matters.
  • Object representations are collections of views that depict the appearance of objects from specific viewpoints’
  • Viewpoint dependent more important for within category discriminations
28
Q

What did Vanrie et al. (2002) propose about Viewpoint dependent and invariant theories?

A
  • Viewpoint dependent = complex within category decisions
  • Viewpoint invariant = easy categorical decisions

Both views could be correct just in different contexts

29
Q

what is the binding problem?

A

how do we integrate different kinds of information to produce object recognition?

30
Q

What is the process of object recognition?

A
  1. object
  2. structural description
  3. semantic representation
  4. name representation
  5. name
  • all or nothing model - you cant get to the next stage if you get stuck at an earlier stage
31
Q

Describe Humphrey’s cascade model?

A
  • structural, semantic and name stages interact.
  • More of interactive account - not an all or nothing account
  • Get inhibition and interaction between stages
  • problems in earlier stage have knock-on effects with later stages, they don’t halt the process all together.
32
Q

what is Agnosia?

A
  • Failure of knowledge or recognition
  • In visual agnosias, feature processing and memory remain intact, and recognition deficits are limited to the visual modality.
  • Agnosia restricted to specific categories
33
Q

Describe Apperceptive Agnosia.

A
  • Problems with early processing (shape extraction).
    ○ All objects may look the same.
  • Perceptual deficit, affects visual representations directly, components of visual percept are picked up, but can’t be integrated, effects may be graded, often affected: unusual views of objects.
34
Q

What is the test for Apperceptive Agnosia?

A
  • ability to recognize degraded or altered-view stimuli is impaired.
  • perceptual deficit - problem in early processing.
35
Q

What is Associative Agnosia?

A
  • Problems with later processing (recognition).
  • Visual representations are intact, but cannot be accessed or used in recognition. Lack of information about the percept.
  • Can copy drawings of objects but cannot name them

Action & Perception (7 decks)

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