Visual perception (Part 2) Flashcards
What are Gestalts principles
Visual principles that interpret stimuli according to principle that the whole is greater then its sum parts
List the 4 different Gestalt principles
- Figure-ground organisation
- Closure
- Similarity
- Proximity
Describe figure-ground organisation (GP)
Organising a scene by differentiating the FIGURE away from the GROUND (eg. contour lines)
Describe closure (GP)
Mentally filling any gaps in stimulus to perceive as whole
Describe similarity (GP)
Mentally grouping objects with similar qualities (shape, orientation, texture)
Describe proximity (GP)
Mentally grouping objects based on position
Define depth perception
- Images captures by our retinas
- Ability to interpret the 3d world
What are binocular depth cues?
- Depth cues relying from both eyes
What is retinal disparity? (BDC)
The cortex uses the degree of differences between the retinal image of left and right eye
What is convergence? (BDC)
The cortex uses the tension placed on the orbital muscle to indicate distance form object
Define monocular depth cues?
Depth perception form one eye
What is accommodation? (MDC)
Eye changes shape to perceive distance
State the 5 pictorial depth cues and briefly describe
- Linear - convergence of parallel lines
- Relative size - objects cast longer retinal images when they’re closer
- Interpretation - If an object is obscured the object is closer
- Texture gradient - finer details indicated distance
- Height in visual field - objects closer to horizon are further
Describe visual consistencies
Principles that help maintain perception
What are the 3 visual consistencies?
- Size - objects are stable despite changes on retinal image
- Shape - objects are stable despite shape on the retinal image (linear perspective)
- Brightness - objects are stable despite brightness
What is the perceptual set?
seeing situations how we expect to see them
What influences perceptual set?
- Past experiences
- Context
- Motivation
- Emotion
Define social influence of visual perception
Interpersonal and environmental factors that effect perception
Define ethnocentrism and its issues
- Perceiving your culture/ society as superior
- Can create biased, ethical issues
What was Hudson, W (1960) aim?
Investigating pictorial depth perception for 3D and 2D images for African vs Caucasian cultures
What was the sampling of Hudson’s 1960s experiment?
6 groups that were schooled (3 x Caucasian, 3x African)
5 groups without schooling ( 1x Caucasian, 4x African)
What was Hudson’s 1960 method, results and conclusion?
Method: asked about their perception of a series of 2d and 3d objects
Results: Without schooling were able to perceive 2d, not 3d. there was a higher 3d perception rate in Caucasian sample vs Africans
Conclusion: there ARE cultural differences in perception
What were the strengths and weaknesses of Hudson 1960?
Strengths: controlled sample, first research indicating social norms affect perception
weaknesses: generalization for population, ethnocentrism
What was Deregowski’s 1972 experiment aim?
Research into if pictorial perception relies on learning. Tested western and African countries. 5 studies were conducted
Describe Deregowski’s Study 1 (method, results)
method: used Hudson’s pictorial depth and people were questioned eg. “which animal is nearer to the elephant?”
results: African community had difficulty perceiving pictorial depth
How did Deregowski classify his two groups?
2D and 3D perceivers
Describe Deregowski’s Study 2 (method, results)
method: shown drawing of 2 squares and asked what they saw
results: Almost all 3D perceivers built 3D objects, 2D perceivers built 2D
Describe Deregowski’s Study 3 (method, results)
method: Asked to copy a 2-pronged-trident
results: 3D perceivers looked at controlled trident longer, whereas 2D perceivers didn’t differ
Describe Deregowski’s Study 4 (method, results)
method: Participants adjusted light so it appeared the same depth as an object in a picture
results: 2D perceivers set light at the same depth (despite what researchers asked) 3D perceivers used depth cues to determine depth
Describe Deregowski’s Study 5 (method, results)
method: used ‘split-type’ drawing to represent animals
results: 2D perceivers preferred these drawings
What were Deregowski’s 1972 conclusion, strengths and limitations?
- Non-westerns lacked pictorial depth
- Strength: Praised for investigating cultural diversity
- Limitations: Ethnocentrism, didn’t include texture gradient
What was Deregowski, Muldrow and Muldrow 1972’s aim?
Presenting drawn familiar objects to remote Ethiopian populations to explore past expenses and perception
What was Deregowski, Muldrow and Muldows sample?
41 Ethiopian participants, 33 lowland, 8 highland
Equal male and female
What was the method of Deregowski, Muldrow and Muldows 1972?
presented 3 pictures in black ink on cloths
1st pic. standing buck
2nd pic. running leopard
3rd pic. hunting scene (similar to Hudons)
Then they were asked open ended questions
What were Deregowski, Muldrow and Muldows 1972 results and conclusion?
- No major difference between groups
- Perception is based on past experiences and familiarity with objects
What were Deregowski, Muldrow and Muldows 1972 strengths and weaknesses?
Strengths: investigated remote population, validity was increased due to experimenter’s familiarity with the area and people
Weaknesses: Violated ethical principles (Ethiopians were distressed), B + W may have changed answers, different answers arose when cloth was moved
Define visual illusion
Consistent misinterpretations of external visual stimuli’s
What was the Muller-lyer illusion?
Two verical lines with arrow head and feather head
What is the carpenter world hypothesis?
The lines at the end of stimuli imply depth due to our experiences with right angles through pictorial depth cues of linear perspective and relative size
Explain the Ames room illusion
We maintain shape consistency of the room as rectangular at the expense of size consistency of the people in the room
Explain the Ponzo illusion
2 diagonal converging lines and is observed further away (height and visual field cue)
What are ambiguous figures?
Multiple stable perceptions that manipulate Gestalts principles
What are impossible figures?
Stimulus that can not occur in reality by manipulating pictorial depth cues
