Week 2: Visual Perception Flashcards
What is the difference between sensation and perception?
Sensation is the detection of physical stimuli and transmission of that information to the brain.
Perception is the brains further processing, organisation and interpretation of the sensory information
Describe monocular, oculomotor and binocular cues
- Monocular cues - require one eye
- Oculomotor - depend on sensations of muscular contracts around the eye
- Binocular cues require both eyes together
What are the five monocular depth cues?
- Linear perspective
- Texture
- Shadows & shading
- Interposition
- Motion Parallax
Describe linear perspective
Parallel lines pointing directly away from us seem progressively closer together as they recede into the distance
Describe interposition
Where a nearer object hides part of a more distant object from view.
If one object hides another we assume it has to be closer, implying depth
Describe Motion Parallax
Where nearby objects appear to move in the opposite direction while distant objects appear to move in the same direction
Describe the oculomotor cues - vergence and accommodation
Vergence is the amount of movement required to focus on an object.
Accommodation is the thickening of the eyes lens when you focus on a close object.
Both only provide info about a single object that is very close to the observer
Describe the binocular cue stereopsis
When there is a slight difference in images projected projected on the retinas of the two eyes when you view an object known as binocular disparity.
What happens when there are small conflicts between cues?
Additivity and weighting of more reliable cues
What happens when there are large conflicts in cues?
One cue dominates the others
What are the five size cues?
- Perceived distance
- Familiar size
- Open-object illusion
- Body size effect
- Functional interactions
What is blindsight?
When people report having blindness in part of their field of vision but still respond to motions and objects in the field they claim to be blind
Describe type 1 and type 2 blindsight
Type 1: patient reports no conscious awareness of any kind
Type 2: patient reports the feeling that something has occurred in the blind field but denies perceptual awareness of it
What are visual cortical area V1 & V2 involved in?
Crucial for visual processing
What are visual cortical area V3 & V3a involved in?
Process vision - particularly moving stimuli
What is visual cortical area V4 involved in?
colour and line orientation detection
What is visual cortical area NT or V5 involved in?
motion perception
Patients with blindsight have damage to what visual cortical area?
Damage to V1 - utilise alternative pathways
What is subliminal perception?
Occurs when a person is able to perform above chance on a task but has no awareness of the stimulus
What are objective measures in subliminal perception testing?
Forced choice response
Reaction time
Neuroimaging
What are subjective measures in subliminal perception testing?
Self-reports
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