The Psychology of Visual Perception: Seeing is Perceiving

Question 1

What is meant by visual sensation?

Answer 1

The process of detecting and receiving stimuli from the environment.
The reception of light by rods and cones in the retina, which is converted to neural signals via tranducstion and transmitted to the brain via the optic nerve as action potentials.

Question 2

What is meant by visual perception?

Answer 2

The processing (organisation and interpretation) of sensory information that occurs after information is transmitted to the brain
Enables us to recognise and understand objects and events.
Combines neural signals with prior knowledge, expectations and beliefs to make sense of sensation.
Is an active process and can result in different people with differential experiences.

Question 3

What are the three processes involved in perception of vision?

Answer 3

Selection
Organisation
Interpretation

Question 4

What is the process of selection during visual perception?

Answer 4

The external environment is too detailed to process everything we ‘see’.
Therefore we our selective based on out attention and filter out irrelevant overload stimuli
Our attention is influenced by emotional significant and our current goals.
Can be bottom up or to-down
Can be affected by fatigue and stress.

Question 5

What is meant by inattentional blindness?

Answer 5

Failure to percieve fully visible stimuli is not selected/attended to.

Question 6

What is meant by change blindness?

Answer 6

The failure to percieve a substantial visual change.
Our eyes may look over a stimuli but we may not perceive it.

Question 7

What is meant by bottom-up and top down visual processing?

Answer 7

Bottom up: Data driven - starting with the information derived from stimuli. Based on stimuli qualities such as colour, orientation and size.

Top down: constructivist, process starting with preexisting knowledge e.g experience, location, meaning. Based on the context of the stimuli, past experiences and knowledge. Often gives a faster more effective response.

Question 8

What is meant by organisation in visual perception?

Answer 8

Organsing and groupin items to percieve them as one
Organise based on patterns/principles
Automatically produces the simples organisation to reduce overload.
We can switch interpretation in certain conditions.

Question 9

What are the different laws of perception in Gestalt psychology relating to vision?

Answer 9

The law of Pragnanz
Figure ground relationship
Perceptual grouping

Question 10

What is the law of Pragnanz in vision perception?

Answer 10

What we see is the simplest and most stable interpretation of the elements
Tend to organise many small more complicated shapes into one larger shape.

Question 11

What is the figure-ground relationship in vision perception?

Answer 11

We distinguish between figures (subject of the image) and the ground of the image.
This draws attention to the figure
This can be affected by how we interpret sensory information, struggle or change what we see as the figure or ground

Question 12

What is perceptual grouping as a law of visual perception?

Answer 12

1. Closure - we see things a s complete wholes rather than segments, we fill the gaps between missing lines to make full shapes
2. Good continuity - more likely to perceive smooth continuities rather than abrupt changes in lines.
3. Proximity - placed together seen as one large object (one big square rather than 16 small ones)
4. Similarlty - rows of shape, size, colour of orientation.

Question 13

What is interception during visual perception?

Answer 13

Giving meaningful experience, including colour, depth and distance to what we see.
This is different to an absolute replication of the visual world
If influenced by stimuli and surroundings cues
Information can conflict.

Question 14

What is depth perception and how do we do it during vision?

Answer 14

Images form on retina on 2D, depth perception allows us to perceive this as 3D
1. binocular cues - over short distance, use both eyes to compare retinal disparity and convergence
2. Monocular cues - one eye, judge gradient, relative size and position on horizon, long distances. Use speed of motion and familiar size to work out distance.

Question 15

How does depth perception develop over time?
How do we know this?

Answer 15

The visual cliff experiment shows that between 2 and 6 months babies can understand and perceive depth.
Show anxiety and avoidance of sudden changes in depth as understand danger of fall.
Suggests has a evolutionary advantage.

Question 16

What is meant by perceptual constancy?

Answer 16

Depth perception supports us to perceive an object as being the same under a variety of conditions.
Tends to see familiar objects as always the same regardless of the perspective, distance or lighting - assumption based rather than actual stimulus.

Question 17

What is perceptual set?

Answer 17

The biases, experiences and expectations we bring to bear when interpreting a visual field give us a mental predisposition to see something in a certain way by focusing on particular features of a stimulus and ignoring others.
Can result in differing perception of the same object/scence compared to what is actually there - creates visual illusions.
Common illusions with circle and line size when portrayed in different environments.

Question 18

What is a perceptual bias?

Answer 18

A predisposition to interpret a stimulus a certain way
Context and past experience
Expectancy- set
Instruction and framing effects - e.g told to be cautious to see something
Motivation (hunger, thirst)
Emotion (anxiety, depression and anger)
Individual differences
Perceptual biases can lead to perceptual error.

Question 19

How does instruction and framing influence perceptual bias?

Answer 19

Predispose to see or not see something - changes focus
NHS - asking to be cautious to look for certain results inc false positives
Framing - can influence perception and risk and decision making (active perception)

Question 20

How does motivation and emotion affect perceptual bias?

Answer 20

We see what we are motivated/primed to see
Emotions influence perception and interpretation of events

Question 21

How does expectation influence perceptual bias?

Answer 21

People see what they are expected to see
Results in change blindness - block out actual perception in favour for what we wanted.

Question 22

Name some different perceptual disorders.

Answer 22

Visual agnosias
Apperceptive agnosia
Associative agnosia
Prosopagnosia
Capgras syndrome

Question 23

What is visual agnosias?

Answer 23

An impairement to recognise visually presented objects, reliant on other senses to recognise>
But all other aspects of vision such as colour, acuity etc is normal - can see but not perceive.

Question 24

What is apperceptive agnosia?

Answer 24

Unable to recognise by shape, cannot copy drawings.
Abnormality in perceptive and discriminative fields, despite having no difficulty in primary visual function.

Question 25

What is associative agnosia?

Answer 25

Can copy shapes
Cannot associate meaning with the shapes.

Question 26

What is prosopagnosia?

Answer 26

Inability to recognise faces only
Requires others senses, not vision, to identify people.

Question 27

What is Capgras syndrome?

Answer 27

Inability to recognise known people, percieves facial similarity but thinks have been replaced by an imposter.
Belief that they have been replaced by an imposter.

Question 28

What is the clinical relevance of perceptual error?

Answer 28

Premature acceptance of most favoured diagnosis is one of the most common causes of diagnostic error - linked to expectations - Inattentional bias
Radiology department - diagnostic errors are the most common error
Biases also apply to perception generally - told painful more likely to be painful, given mortality rather than survival rates more likely to feel worse/better.