Perception Flashcards

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1
Q

Lens

A

Focuses light as it enters the eye

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2
Q

Retina

A

Contains photoreceptors (rods and cones) which transduce light into electrical signals (action potentials)

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3
Q

Fovea

A

The centre of the retina which contains the highest density of cone receptors. Supplies the brain with fine-
grained details and colour

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4
Q

Visual pathway

A

Visual information travels from eyes to Lateral Geniculate Nucleus (LGN) -> Calcarine sulcus in V1 -> Feature detectors -> hierarchical processing from V1 to the temporal and parietal lobes could bind line features into complex shapes

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5
Q

Contralateral mapping

A

Light coming from the left side of space (left visual field) is sent to the right hemisphere (left visual cortex) and vice versa

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6
Q

What makes visual perception hard? Solution?

A
  • Objection constancy
  • Inverse projection problem
    Solution: Unconscious Inference
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7
Q

Object constancy

A

The very same object can project a different image on your retina because of:

  • Viewing angle
  • Lighting
  • Distance
  • Partial occlusion
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8
Q

Inverse projection problem

A

Each 2D retinal image could reflect infinitely many distinct 3D stimuli

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9
Q

Likelihood principle

A

We perceive the object that is most likely to have
caused the pattern of stimuli that we received
- Views perception as a form of problem
solving
- We unconsciously and automatically draw
inferences that are based on experience and
basic principles of simplicity

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10
Q

What does the likelihood principle allow?

A

Top-down biases on perception (top-down processing = Processing that involves a person’s knowledge or expectations)

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11
Q

Bayesian Inference Models

A

The idea that our estimate of the probability of an outcome is determined by the prior probability (our initial belief) and the likelihood (the extent to which the available evidence is consistent with the outcome).*

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12
Q

Gestalt psychology

A

Involves heuristics (a “rule of thumb” that provides a best-guess solution to a problem) used by the visual system in order to perform figure ground segregation (identifying a figure from a background)

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13
Q

Gestalt principles

A
  • Similarity
  • Closure
  • Proximity
  • Good continuation
  • Good figure/simplicity
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14
Q

Similarity

A

Points which share features are grouped together

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15
Q

Closure

A

Points form closed (whole) objects

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16
Q

Proximity

A

Points close in space are grouped together

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17
Q

Good continuation

A

Points are assumed to be connected by smooth lines

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18
Q

Good figure/simplicity

A

Every stimulus is seen as being as simple as possible

19
Q

Environmental Regularites

A
  • Physical regularities

- Semantic regularities

20
Q

Physical regularities

A

Regularly occurring physical properties of

the environment. Examples are light from above assumption and oblique effect

21
Q

Light from above assumption

A

Assume that 3D objects are lit from above

22
Q

Oblique effect

A

People are better at processing horizontal and

vertical lines because they are more common than oblique. Caused by neural plasticity

23
Q

Semantic regularities

A

The characteristics associated with the

functions carried out indifferent types of scenes. Example is Palmer’s scene schema experiment

24
Q

Scene schema experiment

A

Participants recognize schema consistent objects (bread) 80% of time but incongruent objects (mailbox) only 40% of the time

25
Q

Monocular depth cues

A
  • Familiar Size
  • Occlusion and Interposition
  • Texture Gradient
  • Linear Perspective
  • Relative Size/Height
26
Q

Binocular depth/distance cues

A
  • Convergence: the extent to which your eyes are turned inward to fixate an object. Only works for short distances (<1m)
  • Stereopsis/retinal disparity: the difference in image projected to the left and right eye; used to make 3D movies appear 3D
27
Q

Theories of object recognition

A
  • Objected centred

- Viewer centred

28
Q

Object centred theories

A

Propose that we store one 3D template for each object (parts + their relationships)

29
Q

Viewer centred theories

A

Propose that we store many view-specific templates for each object (e.g. at different angles)

30
Q

Pros of object centred theories

A
  • Only requires one representation per object

- Can explain why some views are hard to recognize (hidden geons)

31
Q

Cons of object centred theories

A
  • Can’t discriminate objects that share geon configurations

- Absence of physiological evidence

32
Q

Pros of viewer centred theories

A
  • Natural views exist
  • Recognition time depends on viewpoint
  • Aligns with physiological data
33
Q

Cons of viewer centred theories

A

Requires a lot of stored representations

34
Q

So object centred or viewer centred?

A

Aspects of both theories seem to be important & the brain could do both. Now researchers try to understand how people learn to infer 3D shapes from multiple viewpoints

35
Q

What is perception for? (Marr’s computational level)

A
  • Perception evolved so that animals could act on their worlds
  • Suggests that perceptual and motor systems must be intimately connected
36
Q

How do actions help us perceive?

A
  • The inverse projection problem becomes less of a problem when you can move around
  • Multiple viewpoints help us to better infer the two 3D structure of objects
37
Q

Object Discrimination

A

“What” task - monkeys had to select food wells based on the object covering the well

38
Q

Landmark Discrimination

A

“Where” task - monkeys had to select food wells

based on their closeness to the landmark object

39
Q

Interactions between perception and action streams

A
  • Mirror neurons

- Functional connectivity

40
Q

Mirror neurons

A
  • di Pelligrino et al discovered that single neurons in the monkey premotor cortex fire when monkeys perform OR perceive a specific action!
  • Mirror neurons have since been argued to support empathy and theory of mind: the representation of other’s intentions
  • Debatable whether humans have them
41
Q

Functional connectivity

A
  • Brain regions in the dorsal and ventral stream talk to each other during perception and action
  • Neuroimaging studies measuring functional connectivity show that information in these pathways could be integrated through connectivity
42
Q

Neural plasticity

A

How changes in neural activity after learning a new stimulus occur

43
Q

“What” pathway

A

Striate cortex -> temporal lobe, object discrimination

44
Q

“Where” pathway

A

Striate cortex -> parietal lobe, landmark discrimination