Perception Flashcards
Sensation
Information coming into the brain through stimulating the 5 senses
Perception
Brain interpreting sensory information to give it meaning
Types of depth cue
- monocular
- binocular
Monocular depth cue
Depth cue interpreted through 1 eye
Monocular Depth Cues
- height in Plane
- relative Size
- occlusion
- linear Perspective
Height in Plane
Objects higher up in our visual field appear further away
Relative Size
The more distant an object, the smaller it will be on your retina
Occlusion
An object overlapping another will appear closer
Linear Perspective
Parallel line that appear to get closer together in the distance
Binocular depth cue
Depth cue interpreted through 2 eyes
Binocular Depth Cues
- retinal Disparity
- convergence
Retinal Disparity
- difference between an image from the right and left eye
- bigger difference means object is closer
Convergence
- muscular information provided by angle of focus
- eyes point closer together when object is nearer
Gibson’s direct theory of perception DATE
1966
Gibson’s direct theory PARTS
- perception
- optical array
- bottom-up
- optic flow patterns
- motion parallax
- nature
Gibson’s direct theory PERCEPTION
Sensation and perception are the same thing
Gibson’s direct theory OPTICAL ARRAY
Optical array (field of vision) contains enough info for us to directly perceive
Gibson’s direct theory BOTTOM-UP
Eyes tell brain what is being perceived
Gibson’s direct theory OPTIC FLOW PATTERNS
- evidence of direct perception
- e.g - rushing towards stationary point, object appears still, surroundings blur in FOV, ‘flow’ is direct signal to brain we are moving
Gibson’s direct theory MOTION PARALLAX
- monocular depth cue
- e.g in car - furthest things (sheep in distant field) appear to move slowly, nearest things (nearby hedges) whiz by quickly
- helps more accurately perceive depth/distance
Gibson’s direct theory NATURE
Important as we are born with perceptual abilities (innate)
Gibson’s direct theory STRENGTHS
- developed using real world research
- Gibson studied pilots in WW2 landing planes with damaged instruments, concluded they were relying on motion parallax and other depth cues (like ground texture)
- good ecological validity
+ - supporting research from infants
- Gibson and Walk (1960) - human/other infants reluctant to crawl over safe steep visual cliff drop
- suggests they were born with innate perceptual abilities, theory has more real-world validity
Gibson’s direct theory WEAKNESS
- struggles to explain how visual illusions trick brain
- e.g. Ame’s room - brain struggles to understand people are same size
- goes against theory as we should be able to directly perceive it
Explanations of Visual Illusions
- ambiguity
- misinterpreted depth cues
- fiction
- size constancy
Ambiguity
When there are 2 possible interpretations of the same image - brain finds it hard to choose
Misinterpreted depth cues
Brain tricked into interpretting distance when it isn’t there
Fiction
Shapes using illusory contours to suggest something else is there when it isn’t
Size constancy
Keeping original perception of size of an object, even when information received by eyes changes
Visual illusions
- Ponzo illusion
- Müller-Lyer
- Rubin’s vase
- Ames room
- Kanizsa triangle
- Necker cube
Ponzo Illusion Explanation
- misinterpreted depth cues
- linear perspective - two outer lines converging give impression of depth
- past experiences - train tracks
- brain mentally enlarges top line
Müller-Lyer Explanation
- misinterpreted depth cues
- past experiences - unconsciously perceive inwards arrows as inside corner of building (stretching towards us), outwards arrows as outside corner of building (stretching away from us)
- perceive line as longer when arrows point inwards
Rubin’s Vase Explanation
- ambiguity
- 2 equally possible interpretations - brain struggles to choose between background/foreground so image appears reversible
Ames Room Explanation
- size constancy
- room is not square, rear wall is slanted further back on the left but appears a normal room at right angles with smaller person on left
Kanizsa Triangle Explanation
- fiction
- illusory contours create impression of another triangle as perceptual system creates image that fills gaps to create something plausible
Necker Cube Explanation
- ambiguity
- brain can’t decide where front is as image perfectly balanced so can be seen from multiple viewpoints
Gregory’s constructivist theory DATE
1970
Gregory’s constructivist theory PARTS
- top-down
- inferences
- visual cues
- nurture
- environment
Gregory’s constructivist theory TOP-DOWN
- perception is top-down process
- construct our reality using brain to make guesses about what we are perceiving
- the brain tells the eyes what to see
Gregory’s constructivist theory INFERENCES
Make inferences about what we are perceiving based on past experiences
Gregory’s constructivist theory VISUAL CUES
Relied on to help measure things like depth and distance
Gregory’s constructivist theory NURTURE
- how we perceive is learnt
- things like culture have big impact on how we perceive
Gregory’s constructivist theory ENVIRONMENT
- environment we are brought up in will affect how we perceive
- e.g - people from West fall for Müller-Lyer illusion (brought up with rectangular buildings), people brought up in rainforest won’t mistake depth cues so won’t fall for illusion
Gregory’s constructivist theory STRENGTH
- supporting research evidence
- Hudson (1960) found different cultures perceived 2D image of elephant + hunter in different ways
- supports idea we learn to perceive through nurture/experiences + rely on visual monocular depth cues like height in plane to perceive
Gregory’s constructivist theory WEAKNESSES
- opposing research
- Fantz (1961) found babies are born with perceptual abilities, would prefer images of human faces from birth
- goes against Gregory’s nurture idea, suggests some perceptual abilities innate
+ - opposing theory
- Gibson’s theory may be better at explaining everyday perception, Gregory’s theory explains why we fall for ambiguous visual illusions deliberately designed to trick us (like the Necker Cube)
- Gibson’s theory may be more ecologically useful
Perceptual Set
The tendency or readiness to notice certain aspects of our sensory environment
Factors affecting perceptual set
- motivation
- expectation
- culture
- emotion
How does motivation affect perceptual set
Wanting something increases it’s attractiveness and we notice it more
Gilchrist and Nesburg DATE
1952
Gilchrist and Nesburg AIM
- study effects of motivation on perceptual set
- see if hunger is motivating factor affecting perception
Gilchrist and Nesburg METHOD
- lab experiment
- 26 undergraduates
- independent groups - half food deprived for 20 hours, half not
- showed food (steak,chicken) on projector for 15 seconds, turned off, made to readjust to original brightness
- Ps told it was matching pictures exercise
Gilchrist and Nesburg RESULTS
- food deprived Ps perceived + made images brighter
Gilchrist and Nesburg CONCLUSION
- hunger is motivating factor affecting perceptual set
Gilchrist and Nesburg STRENGTH
- similar results in other studies
- Sanford (1963) showed food deprived Ps ambiguous pictures, saw brown blobs as burgers
- Gilchrist and Nesburg have strong reliability, motivation more likely to be factor affecting perceptual set
Gilchrist and Nesburg WEAKNESSES
- ethical issues
- protection from harm - discomfort caused, consent given but may not have realised effects so may not have been fully informed
- may be considered unethical, may not have been worth it for psychological research
+ - artificial task
- images of food used, when food presented in real life, other sensory factors like smell influence perception
- low ecological validity, results may not be applicable to how motivation affects perception of food in real world
How does expectation affect perceptual set
When we expect something to happen, we are more likely to notice it
Bruner and Minturn DATE
1955
Bruner and Minturn AIM
- see if expectation is a factor affecting perceptual set
- see if anticipating seeing something makes it more likely you will
Bruner and Minturn METHOD
- 24 students
- lab experiment
- independent groups
- 1 condition shown letters A + C stimulus on screen
- 1 condition shown numbers 12 + 14 stimulus on screen
- both groups flashed ambiguous figure inbetween for 30 milliseconds, looked like B/13
- Ps made to write down what they saw
Bruner and Minturn RESULTS
- most Ps shown letters stimulus drew ‘C’
- most Ps shown number stimulus drew ‘13’
Bruner and Minturn CONCLUSION
Expectation affects perceptual set as Ps perception of ambiguous figure easily influenced by stimulus shown
Bruner and Minturn STRENGTH
- explains perceptual errors
- US navy cruiser in 1988 shot down civilian plane knowing there was military action nearby, expectation affects perception, knowing context can reduce errors in judgement
- gives study real world application
Bruner and Minturn WEAKNESSES
- artificial task
- ambiguous figures not found everyday, visual illusions deliberately designed to trick us
- doesn’t show how everyday perception is affected by expectation, low ecological validity
+ - problems with experimental design
- independent groups, Ps only did 1 condition of IV, may be participant variables, may be Ps whose name begins with ‘B’ or Ps who are superstitious about ‘13’
- may be weaker reliability of findings
Culture
Beliefs and expectations that surround us
How does culture affect perceptual set
People from different cultures may perceive same object/situation differently due to the different cultural norms, values, beliefs
Culture study METHOD
- schooled/unschooled Ps
- show man hunting deer + giraffe in distance - say who man is hunting
- height in plane + relative size shows deer is closer
Culture study RESULTS
More schooled Ps to perceive depth and complete task successfully than unschooled
Culture study CONCLUSION
People from different culture/ background have different perceptual set
How does emotion affect perceptual set
- notice things we find exciting
- takes longer to perceive something unpleasant
- block out things we find threatening
Emotion study METHOD
- flash emotionally neutral (tree) + taboo (penis) words
- make Ps say words out loud
- measure time taken to say word + emotional arousal using GSR
Emotion study RESULTS
Offensive words take longer to say and have higher change in emotional arousal
Emotion study CONCLUSION
- emotion affects perceptual set
- perceptual defence used by brain with offensive or anxious words
