Block 2 - When perception goes wrong ( Top-up down)

Question 1

What is wrong with the bottom up theories of perception, what question do we ask from this?

Answer 1

-This theory assumes that perception is always accurate, but this isn’t the case
- So, do retinal images fully determine perception?

Question 2

Describe what top-down theories think about perception?

Answer 2

Perception > sensation
Retinal images needs to be interpreted
Perception is not automatic - cognitive processing is needed

Question 3

Name some examples of erroneous perceptions ( visual illusions)?

4

Answer 3

-Fraser Spiral illusion
-Vertical - horizontal illusion
-Jastrow illusion
-Irradaition illusion

Question 4

What is the Fraser spiral illusion, how does it work?

Answer 4

• This is where you perceive a series of concentric circles to be spirals
  -This is done due to the misaligned parts ( the black and white strands within the circle ) which distort the perception of regular patterns

Question 5

What is the vertical- horizontal illusion, how does it work?

Answer 5

• This is when we view the vertical line to be longer, even when they are the same length
  Bisecting lines are perceived as being longer than bisected - so our visual systems shorten a line that is dissected by something else

Question 6

What is the Jastrow illusion, how does it work?

Answer 6

Objects that are placed on an imaginary circle at a longer radius, appear to be shorter

Question 7

What is the irradiation illusion, how does it work?

Answer 7

For example, if you had to squares, one with an inner white area and black border, and another with an inner black area and a white border
-We would view the square with the inner white area as larger
This is because light areas appear to be larger than dark areas, because light from the white area, irradiates adjacent black regions

Question 8

So what does these visual illusions ( erronous perceptions) tell us?

Answer 8

what we perceive is not always what is reflected on our retina

Question 9

What is visual ambiguity in perception? ( Equivocal perception )

Answer 9

-There are some figures where we can not always be sure what we perceive

Question 10

What are some examples of ambiguity in perception?

3

Answer 10

-Figure/Ground ambiguity
-Feature ambiguity
-Depth ambiguity

Question 11

What is figure/ground ambiguity?

Answer 11

Figure-ground ambiguity is a visual phenomenon where the perception of what’s the foreground subject (figure) and what’s the background (ground) isn’t clear

For example, one person might see two faces in an image, another might see a vase, despite the visual sensation being the same

Question 12

What is figure ambiguity?

Answer 12

This is where one feature can be two totally different thing

Question 13

What is depth ambiguity? (Necker cu be)

Answer 13

-This is where you can’t be quite sure about the 3D orientation of a cube
-So 3D perception changes in the same retinal image

Question 14

What would Gibson say about these erroneous and ambiguous visual perceptions? Why is he wrong?

Answer 14

-Man-made
-Constructed to mislead
-No ecological validity

Gibson is wrong because we have real world examples of these illusions

Question 15

What are some examples of real world illusion?

Answer 15

-Moon illusion

-Waterfall illusion

-Wagon Wheel effect/ stroboscopic effect

Question 16

What is the moon illusion?
What explains this?

Answer 16

• This is where the moon appears to be lager when it is closer to the horizon compared to when it is up in the sky
  -But the moon is always the same size
  -This is explained by depth/size cues

Question 17

What is the waterfall illusion? What explains this?

Answer 17

This is where you are looking at the moving water of the waterfall, and the objects around it seem to be moving in the opposite direction

Why- Motion aftereffect - Explained by neuronal convergance

So, this happens due to neuronal adaptation to movement - so when we shift our gaze to a static object, our neurons pretend that this movement is still going on, so objects appear to move in the opposite direction

Question 18

What is the wagon wheel effect, what Is this explained by?

Answer 18

What - This is where a moving wheel seems to stand still, or move in the opposite direction of its true rotation (Stroboscopic effect)

Why- Neurons try to make sense of the fast motion of identical objects, by interpolating frames, following the nearest neighbour principle

Question 19

Why do we also have real-life examples of visual ambiguities?

Answer 19

-All of our retinal images could be argued to be ambiguous
-This is because 3D objects a presented on a 2D retinal surface
-This means that many different types of objects that differ in their depth, produce the same retinal image
-Thus making our retinal images ambiguous by nature
-This is known as the inverse projection problem

Question 20

What are some real life examples of the inverse projection problem?

Answer 20

• Superimposed objects
  -Untypical angles

Question 21

Who came up with the Constructivist theory?

Answer 21

-Gregory

Question 22

How did Gregory differ from other perspectives on perception?

Answer 22

-He acknowledged that we are not just automatic perception machines
-We are not just walking through the environment and taking in whatever there is
-We are guided by our experiences expectation and motivation

Question 23

What is the basic idea of the constructivist theory?

Answer 23

• Perecpetion is indirect ( interpreted), and a constructive process of hypothesis testing ( hypotheses that are based on internal factors are used to interpret the sensory input )
• As perception is based on individual factors, incorrect hypothesis can be formed, which can lead to perceptual errors
  -So, yes there is a retinal image, but this image is not sufficient for perception, we need help

Question 24

How can Gregory’s constructivist theory help us explain ambigious figures and visual illusions?

Answer 24

Ambiguous figures -
Ambiguous figures are two likely hypotheses
-These individual factors can lead to these visual illusions

Question 25

Explain perception using Gregorys constructivist theory - using coffee mug

Answer 25

Perception = Interpretation of sensation Coffee mug = The sensory input (round, cup-shaped, smell, …) matches the perceptual hypothesis (based on stored object representations, situational context, personal expectations and motivation, …)

Question 26

What the strengths to Gregorys constructivist theory?

Answer 26

Theoretical account I( tries to explain how perception and object recognition works) Is able to explain perceptual failure ( visual illusion and ambiguity)

Question 27

What are the weaknesses to Gregorys constructivist theory?

Answer 27

Cannot explain why we continue to perceive visual illusions -even when they are known - this is a problem for a theory that assumes that Suggests that perception is not effortless (active and continuous hypothesis testing)- doesn't match our subjective experience

Question 28

What observation did the Gestalt psychologists make? What conclusion did they draw from this?

Answer 28

So when you look at two flashing lights, and you flash them in alternation You don't perceive two flashlights, you perceive a motion So, these researchers concluded that the sensory experience ( Two flashing lights) is not sufficient to explain the perceptual experience ( illusion of movement )

Question 29

What famous phrase did the Gestalt psychologists coin? And what did they mean by this?

Answer 29

The whole is more than the sum of its parts The perceptual experience of motion is more than the some of its parts The parts alone are the two flashlights, but perceiving is more than that Sensation is not sufficient to explain perception

Question 30

What does gestalt actually mean?

Answer 30

Whole configuration

Question 31

So what did gestalt psychologists want to work out? What was their solution to this?

Answer 31

Wanted to work out how we achieve a representation of a whole object Answer- Perceptual organisation

Question 32

What is this perceptual organisation?

Answer 32

Grouping -Putting together elements that form an object Segmentation -Separating different groups of elements

Question 33

What is the physiological evidence of this perceptual organisation?

Answer 33

Remember the centre/surround receptive fields of ganglion cells These are not interested in luminance continuous, but are excited by luminance discontinuities

Question 34

How do we actually do this perpetual organisation, how do we do this grouping/ segmentation?

Answer 34

-According to gestalt psychologists we do this by following a number of principles

Question 35

What are the principles for perceptual organisation ? Remember the mneonomic

Answer 35

Professors Say Clever Gestures Create Remarkable Student Observational Skills. Proximity Similarity Common fait Good continuation Closure Relative size Surroundness Orientation Symmetry

Question 36

Explain the gestalt principle of proximity

Answer 36

- Elements that are close together are grouped together

Question 37

Explain the gestalt principle of similairty

Answer 37

Objects that are similar to each other are grouped together Similarity overrides proximity

Question 38

Explain the gestalt principle of good fait

Answer 38

Elements that appear to move together are grouped together This explains why camegflague animals can be seen when they move, because when they moved they are grouped together and we can see them

Question 39

Explain the gestalt principle of good continuation

Answer 39

Elements that continue together are grouped together

Question 40

Explain the gestalt principle of closure

Answer 40

Elements that close a figure are grouped together

Question 41

Explain the gestalt principle of relative size

Answer 41

We group together elements that are smaller rather than bigger

Question 42

Explain the gestalt principle of surroudness

Answer 42

We group together elements in a surrounded area

Question 43

Explain the gestalt principle of orientation

Answer 43

Group together elements are orientated horizontally and vertically, rather than diagnollay

Question 44

Explain the gestalt principle of symmetry

Answer 44

We lile to grouip together elements that are symmetrical

Question 45

So by applying these gestalt principle, what are we doing?

Answer 45

We are following the law of good gestalt

Question 46

What is the law of good gestalt?

Answer 46

" of several geometrically possible organisation, the one that will actually occur poses the best, simplest and most stable shape"

Question 47

So how does the gestalt psychologist theory explain perception - using the coffee mug analogy?

Answer 47

Perecpetion = The interpretation of sensation, in line