AQA Psychology Unit 3 - Perception

Theories of perceptual development -> Gregory's top down/indirect theory; Gibson's bottom up/direct theory

Development of perception -> depth/distance, visual constancies

Face Recognition & Visual Agnosia -> Bruce and Young, case studies and explanations of prsopagnosia

Constructivist / Indirect / Vision for Perception / Top Down

A01

• Stimuli do not give us enough information - ambiguous, limited - So stimuli is treated as a hypothesis and is tested in different contexts

Research/A02

• Necker Cube -> Illustrates hypothesis testing as cube has no context
• Hollow Face -> we see as normal face as we expect it to be normal
• Brunner et al -> Black hearts in set of cards seen as purple or brown - we expect red and so the colours layer to form brown/purple

• Sanford et al -> B---D = Seen as Bread by hungry participants but Bored by non hungry participants - It is contextual/Situational/Motivational
• Ponzo Illusion -> The lines appear to look like railway track. The first line looks longer as in context of rail track, the lines look shorter the further away they are even though same length so our minds tell us that because they appear to be the same length the first line must actually be longer to make up for the distance
• Gibson's Theory

A03

• Good at explaining errors but others think that if it is hypothese testing then we should have more errors
• alternative theory to consider - Gibson
• Nurture side of debate
• No ecological validity as lab studies and we do not experience visual illusions in everyday life

Direct / Vison for Action / Bottom Up / Innate / Ecological

A01

• Lots of information from Optic Array (patterns of light) -> Gives rise to texture gradients(depth&distance), horizon ratios(distance&size) and optic flow patterns(position&depth) -> Objects give affordances that can change in different circumstances (box can be storage or stool)

Research/A02

• Warren & Hannon 1988 -> A film of moving dots - pps could accurately tell what direction they would be travelling in to see the dots moving how they were - supports optic flow information
• Hahn 2003 -> Two images in slow or quick succession - saw movement when quick but not slow - shows that optic flow is not needed to make judgement of direction

• Sanford 1936 -> motivational factors - B---D = Seen as Bread by hungry participants but Bored by non hungry participants
• Brunner 1951 -> Hearts were black in set of cards not red, pps saw them as purple/brown. Gibson cannot explain this but says it does not matter as artifical
• Gregory's Theory

A03

• Nature/Innate
• Good ecological vailidty
• Real word applications - runways / road markings / pilot training

Nature

• Gibson and Walk 1960 -> Visual Cliff - 6 month old babies places on shallow end and encouraged to cross to deep side by mother - most wouldn't showing depth was percieved. However maybe they had had time to learn it already? Ethics?

Nurture

• Campos et al 1970 -> Visual cliff but tested using Heart Rate. 2 month olds had decrease in hr on deep side showing they perceived change but were not scared. Nine month olds had increased hr showing they were scared as they had learnt to be
• Segall 1966 -> Muller-Lyre illusion to rural tribes in south africa - they said lines were same length - they did not give them context - live in round huts and so did not percieve them how we supposedly do (as corner of room). They did not apply size constancy
• Deregowski 1972 -> Elephant pictures - people in african cultures preffered the unrealistic image as they had not learnt how to draw 'correctly'

Size Constancy Study

Bower 1966 -> 30cm cube 1m away, timed length of time spent looking at cube. compare to same cube 3m away and a 90cm cube 3m away that had same retinal image as bigger but further away, but the 30cm cube 3m away had smaller retinal image. Size constancy found as were 3x more likely to look at the smaller cube than larger one as saw a difference

Shape Constancy Study

Caron, Caron and Carlson 1979 -> 3 month old infants. Some repeatedly shown a square of a trapezoid from various angles but never face on. The experimenters arranged it so that sometimes the trapezoid produced retinal image of a square, and the square produced a retinal image of a trapezoid. After the infants lost interest in the shapes (when they showed habituation), a square of a trapezoid was shown face on. Those who had habituated to the square that produced a trapezoidal shape immediately showed interest in the real trapezoid, and similarly those who saw a trapezoid that produced a square shape were interested in the real square. = The infants habituated to the real shape of the object rather that to the object shape projected on the retina - infants have developed at least partial shape constancy

Infants do not have same visual abilities as adults

• Poor visual acuity (images not as sharp)
• Colour vision is non existant for first few weeks
• Binocular disparity and binocular vision is not found before 3-6 months, and the development has a critical time peroid - Bank et al 1975; adults who had a squint at birth and had surgery by 30 months had good binocular vision but those who were diagnosed between 2 and 7 years old had reasonably good binocular vision, but those who had surgery between 4 and 20 years old had little or no binocular disparity. 
• Innate bias for faces - Johnson et al 1991; found infants in first hour after birth showed more visual tracking of realistic faces than scrambled yet symmetrical faces which suggests some aspect of face perception does not depend on learning. However Turati 2002 suggest they may simply have a preference for stimuli with more patterning in their upper than lower part. This is found in faces and other stimuli.
  

Maturation 

Aspects of development in children owing little to learning or experience i.e. developmental changes resulting from genetically determined factors e.g growing teeth. ->> Maurer 1999; studied infants who had been treated for cataracts in one or both eyes, initially their visual acuity was at newborn level, however after only one hour they had substantial improvement. Therefore prolonged visual experience and learning are not necessary for development of visual acuity.

Methodological problems

Infants cannot tell us what they can see so must rely on indirect evidence based on behaviour - danger then that we may assume infant perception is more similar to adults than is the case

• Segall 1966 -> Muller-Lyre illusion to rural tribes in south africa - they said lines were same length - they did not give them context - live in round huts and so did not percieve them how we supposedly do (as corner of room). They did not apply size constancy
• Deregowski 1972 -> Elephant pictures - people in african cultures preffered the unrealistic image as they had not learnt how to draw 'correctly'
• Gregor and McPherson 1965 -> two groups of austrailian aboriginies, one living in carpentered environment and one in open air basic housing etc. The two groups did NOT differ on the Muller-Lyre illusion, and so cross-cultural difference may depend more on training and education than the environment they grew up in

Evaluation

• Rely on self-report - the differences may actually be a result because of differences in ability to report perceptual experiences accurately i.e. due to language differences
• research has focused on 2D illusions, and such limited research may tell us little about everyday perception. There is large differences in the significance attached to various visual stimuli -e.g african cultures make much more sense of complex footprints than western societies, and chinese texts convey much information to chinese people but none to most of us

Bruce and Young

Bruce and Young's model of face recognition suggests that we recognise faces in a series of three stages.

• In the first you see a set of individual features - Structural Encoding (which consists of View-Centered Descriptions and Expression-Independent Descriptions).
• After they are processed they are combined to form a mental reperensentation of the whole face. This is the second stage of processing and is the analysis of speech and expression, and directed visual processing.
• The third stage is where the face is 'looked up' in the cognitive system/memory and all known information about the face is found from the Face Recognition Units, Person Identity Nodes and Name Generator.

Support for Model

• PET Scans show different areas of brain used in face recognition
• Thompson's Thatcher Illusion
• Bruce and Young 1993 - brain damaged soldiers, part of ffa damaged but others worked so support for modular. Although researcher bias possible
• Bruyer case study - couldn't recognise faces but could from voices

Challeneges

• Cognitive System is not explained fully
• WJ was able to identify faces with no sense of recognition - model does not explain this
• DeHaan 1991 - could name a face but had not other knowledge - goes against model

Modifications

Burton and Bruce 1993 revised the model - no seperate store for names, decisions about familiaritry are in the PIN not FRU, more precise, PC tested, but dtill does not account for the process that allows new faces to be learnt and new identities stored

A03

• Methodology - looks at things that unethical to recreate (brain damage), case studies (generalise? rich data, other problems interfere with findings, demand characteristics)
• Modular vs non modular? DeHaan/WJ
• Reductionist - cognitive/biological
• Brain is complex - model is over simple - does not explain role of neurotransmitters
• Culture differences in face recognition - caucasions more analytical and look at eyes and mouth, but asians look at nose and are more hostillic - Blais 2010

• Visual Agnosia - the inability to recognise familiar objects presented visually - can be apperceptive (physiological) or associative(cognitive)
• Prosopagnosia - the inability to recognise faces - can describe features of a person looking at but not recognise them as a friend or family member etc

Face Specific?

• Barton found that the fusiform face area(FFA) was damaged in people with prosopagnosia more so than people with object recognition problems - asked five people to discriminate faces, and those whose brain damage included the FFA performed poorly compared to those with intract FFA. Although small sample size
• Farah argues that face recognition is different to other forms of recognition - case study on LH - supports as he could identify objects but not faces but there are other case studies that disagree
• Gauthier - people with prospagnosia can have other recognition problems - faces may not be special and may be down to levels of experience - the FFA was activated when it comes down to things people know a lot about eg birdwatchers looking at birds not cars and vice versa