Perception

Question 1

What is perception?

Answer 1

The identification and interpretation of a sensation in order to form a mental representation.

Question 2

What does gestalt mean and what are its principles

Answer 2

Laws for grouping stimuli together all rest on the belief that the whole is greater than the sum of its parts.
- Similarity: perceived as a group - Proximity: tend to be grouped together.
Closure: tend to perceive forms and figures as complete, even when we can’t see all the edges.
- Continuity: We tend to perceive a line continuing its established direction
- Figure ground: Can see two or more images in one.

Question 3

What is depth and how can we infer it?
Describe the pictorial secondary (env) cues.
- all monocular

Answer 3

• inferring distance of objects based on our expectations
• Linear perspective: parallel lines are closer together further back (picture train track picture)
• Relative height – things that are closer tend to be lower in the visual field.
• Texture gradient: pattern in the stones gets smaller (finer texture) further back.
• Interposition: items that are closer will block things behind. Linked to the Gestalt idea of closure.
• Motion parallax: differences in speed- items closer move more quickly

Question 4

What is perceptual constancy

Answer 4

the ability to perceive an object as unchanging, despite changes in the sensory info: size, shape, location, brightness and colour.
Size: retinal image changes on observer distance
Shape: regardless of its orientation/angle.
brightness: changing lighting, colour: changing illumination.

Question 5

What is an illusion?

What are the types

Answer 5

A perception that occurs when a sensory stimulus is present but is incorrectly perceived.
Includes: distortions, ambiguous figures, paradoxical figures and fictions
- Others include those involving apparent movement and shading. an illusion of motion or change in size of a visual stimulus.

Question 6

What does the retina contain

Answer 6

light sensitive cells (visible light) that turn light energy into chemical energy - nerve impulse

Question 7

What are cones

Answer 7

detect colour under normal daylight conditions and allow us to see in fine colour, retina contains 6 million cone cells, mostly located in the fovea.
- the wavelength of light determines the colour that will be perceived.

Question 8

What are rods

Answer 8

become active under low light and are useful for night vision, about 120 million rods on your retina – distributed everywhere except the fovea. Most sensitive to light at 498nm

Question 9

What is the fovea

Answer 9

Centre of focus, visual acuity is best.

Question 10

What is the optic nerve and why are there no light sensitive cells

Answer 10

Nerve impulse carried along.

- There is a blind spot on the retina.

Question 11

What is the occipital lobe and early visual system V1

Answer 11

associated with visual processing

• codes simple features like the orientation of lines.
• Damage to this area causes blindness.
• Cells are sensitive to a specific area of the visual field. 50% of V1 is devoted to interpreting the central 2% of the visual field – the fovea.

Question 12

What 2 pathways process aspects of visual info

Answer 12

• The Dorsal Pathway: where objects are- guides movement, not conscious (blindsight tests)
• The Ventral Pathway: What we can see- is conscious, certain areas specialise in object perception, faces recognition (higher-level processing, whole precepts)

Question 13

How did Hubel & Wiesel investigate the response profiles of individual neurones along the ventral stream.

Answer 13

implanted electrodes into cells in V1 to record the activity of neurones. They found cells that were selective to lines at certain angles in a certain area of the visual field. In some patients with temporal lobe epilepsy, doctors implanted electrodes to identify damaged tissue for surgery planning.
- Quiroga et al. found that some of the patients had cells that were specifically active to certain people such as Jennifer Aniston.

Question 14

What are ambiguous figures

Answer 14

a picture of a subject which the viewer may see as either of two different subjects or as the same subject from either of two different viewpoints. E.g. duck and rabbit.

Question 15

What are paradoxical figures

Answer 15

look ordinary at first but after examination, cannot exist in reality.

Question 16

What are fictions

Answer 16

help explain how we perceive that objects possess specific shapes.

Question 17

Illusions evaluation

Answer 17

• Several studies since the early 1980s have shown that the brain interprets various visual illusions as if they are real.
• Laeng and Sulutvedt (2012) used pupil dilation to reveal the real effects of illusions. They used an infrared sensor to measure the pupil sizes of observers as they looked at a brightness illusion, in which one design seems very much brighter than another, despite the same amount of physical luminance. Participants’ pupils constricted more in response to the subjectively brighter design: a subjective experience of brightness, rather than an objective measure, governs the response (traditionally thought of as involuntary). This demonstrate that we have no direct contact with reality.

Question 18

How do top-down (conceptually driven theorists explain perception?

Answer 18

an indirect process that involves making inferences about the info from the senses. Construct our perception of the world Based on knowledge and expectations of the world.

Question 19

What do illusions show about perception?

Answer 19

• how our visual system groups characteristics of an image reflects some innate properties of the way the visual system is wired
• What we perceive is an interpretation of the data provided through our senses, which makes the basis of knowledge ‘indirect.

Question 20

We often supplement perception with unconscious inferences. What can this be illustrated by?

Answer 20

Misapplied size constancy theory account of the Muller-Lyer illusion, outside or inside corner. Due to the perceptual system misperceiving the lines as being different distances from the observer, which in turn, affect their relative perceived sizes.

Question 21

Evaluation of Gregory (top-down approaches in perception)

Answer 21

• If perception is constructive why are there common experiences of different people. In Gordon’s view, constructivist theories have underestimated the richness of sensory evidence in the real world.
• Much more successful at explaining illusions, theory may be most relevant when stimuli are ambiguous or incomplete, presented very briefly

Question 22

How do bottom-up theorists explain perception

How does Gibson build on this?

What is the optic array and how does it pick up info?

Answer 22

• is a direct process, determined by the information presented to the sensory receptors
• Perceptual set acts as a selector and interpreter and can be induced by perceiver/organismic variables– include expectations, which often interact with context e.g. wishful seeing (without awareness, may be to achieve our goals) and stimulus/ situational variables.
• directly ‘picking up’ the rich information provided by the optic array (information about the layout and properties of objects in space), with little or no (unconscious) information processing, computations or internal representations.

Question 23

What are features of the optic array?

What are they all?

Answer 23

Optic flow patterns (OFPs: changes in the optic array as the perceiver moves about),

• texture gradients
• affordances
• are all invariant, unchanging and ‘higher-order’ features

Question 24

2 criticisms for Gibson (bottom-up perception)

Answer 24

• overlooked the role of culturally determined knowledge in perception. People see objects and events as what they are in terms of a culturally given conceptual representation of the world.
• failed to distinguish between seeing (says much more about this) and seeing as, the latter forming the basic principle of transactionalism.
• Marr claims that Gibson failed to recognise the sheer difficulty of the detection of physical invariants, like image surfaces, which is an information-processing problem.

Question 25

Compare similarities and differences between Gregory and Gibson

Answer 25

• agree that visual perception is mediated by light reflected from surfaces
• perception is an active process, influenced by learning (making them empiricists), although they propose different kinds of learning. Gibson is also a nativist in certain respects and was influenced by the Gestalt Psychologists.
• Gregory believes that meaningless sensory cues must be supplemented by memory, habit, experience and so on, in order to construct a meaningful world. Gibson argues that the environment (initially the optic array) provides us with all the information we need for living in the world. Bottom-up processing (Gibson) may be crucial under optimal viewing conditions, but under sub-optimal conditions, top-down processing (Gregory) becomes increasingly important.

Question 26

Support for Gibson

Answer 26

• Lee and Lishman support Gibson’s belief in the importance of movement in perception, and the artificiality of separating sensory and motor aspects of behaviour. Experiments on effects of room tilting on body sway.

Question 27

Who suggested both bottom-up and top-down processes are probably needed

Answer 27

Neisser’s analysis-by-synthesis model shows perception is an interactive process, involving both bottom-up feature analysis and top-down expectations (appearing at different stages of a perceptual cycle)

Question 28

Describe Marr’s computational theory

Answer 28

maintains that vision’s main function is to derive a representation of object shape from information in the retinal image. This is achieved via a series of four increasingly complex stages/modules: the image/grey-level description, the primal sketch, the 21⁄2-D sketch, and the 3-D model representation/object r
- analyses vision as an information processing task.

Question 29

Describe the non-pictorial primary cues (within-organism)

Answer 29

• Can be monocular: Accommodation: accommodate more to closer objects.
  Or binocular:
• Convergence: converge at close, diverge at far objects
• Binocular disparity- difference in the retinal image of the two eyes provides information about depth. (finger thing)