Lecture 6 Flashcards
What is the bottom-up process of perception?
DATA DRIVEN
- Environmental simulation
- -sensory process–> - Sensation(being received): Retinal image (only sensory fragments of angles and lines)
- Perceptual Organisation(processes info): Figure seen as rectangle turned away away from you
- -Organisation, Depth, Constancy–> - Identification/Recognition: Recognised as member of picture category
What is the top down process of perception?
CONCEPTUALLY DRIVEN- by higher order processes
- Mental Processes
- - Expectation, beliefs,Knowledge, Memory, Language–> - Identification/Recognition: Recognised as member of picture category
What is perceptual organisation?
organisation of a continuous array of sensations into meaningful units
Perception is not fixed/absolute - single image can have multiple interpretations (old woman with big nose or young woman with necklace)
What are the 4 aspects of perceptual organisation?
- Form perception
- Depth or distance perception
- Motion perception
- Perceptual Constancy
What is Form perception?
Organises sensory information into meaningful shapes and patters
(giraffe picture)
Gestalt view
What is the Gestalt view?
The whole is more than the sum of the parts
What are the Gestalt principles?
Underlying principle: We tend organise visual elements into two groups or unified wholes
- The law of Proximity - group nearest elements - see rows not columns
- The law of Similarity - group most similar elements - see square of Os inside Xs, not mixed columns
- The law of Good Continuation - see lines as continuous even when interrupted - arrow piercing heart not separate 3 elements
- The law of Closure - fill in the gaps to experience as whole
- The law of Common Fate - Group objects moving in same direction - alternative rows moving apart
What is Distance or Depth perception?
The organisation of perception in 3 dimensions
Visual information provides important information about depth and distance (Monocular cues, Binocular cues and Motion parallax cues)
What are the 7x Monocular Depth perception cues?
Uses visual input form one eye
- Interposition
- Linear Perspective
- Texture Gradient
- Shading
- Aerial Perspective
- Familiar size
- Relative size
What are the 2x Binocular Depth perception cues?
Uses visual input integrated from the two eyes
Retinal disparity
Convergence
What are the 2x Motion Parallax Depth perception cues?
relative distance from viewer determines amount and direction of relative motion
see a car that is far away as Stationary even though it is moving towards you
Rods in retina and neurons are sensitive to motion
1. Eyes stationary and object moves
2. Eye moves with the object, keeping the object on the same place of the retina
What is retinal disparity?
Each eye gets a different picture of the world
The greater the difference between pictures the closer the object
What is convergence?
Eyes point inwards when looking towards close objects
Eyes move outwards when looking at distant objects
Cue about depth
What is perceptual constancy?
Ability to maintain an unchanging perception of an object despite variations in retinal image
Impossible images plays with perceptual constancy
What are the three main types of Perceptual constancy?
Size Constancy
Shape constancy
Lightness constancy
What is Shape constancy?
Retinal image different from each position but still perceives as rectangle
What is Lightness constancy?
Tendency to perceive whiteness, greyness, blackness of objects across changing levels of illumination
Dim lit room –> Bright outside
What is the Muller Lyer Illusion?
example of Size Constancy
Length of line with arrow ends inwards or outwards/ done with room walls/corners
Note: african village members
What is Size Constancy?
Ability to perceive the true size of an object despite variations in the size of the retinal image
Someone doesn’t grow bigger if they walk towards you even though they look bigger
What is the Ames room?
An example of size constancy
Perceive the room is rectangular therefore think the people are on same lines
What is the role of attention in perception?
We actively search the environment in order to make sense of it
We can only process a finite amount of information (some gets screened out according to attention)
What we attend to determines what we perceive (gorilla)
-Goal directed selection (certain clothes you want to buy)
-Stimulus driven capture (traffic lights)
Motivation -e.g. hunger - cafe, more likely to smell food when hunger than when not
What was the Inattentional Blindness trial and its study conclusion?
20/24 radiologists (83%) and all naive observers failed to report seeing a gorilla in the scan
Study conclusion: the message go the present set of results id that even this high level of expertise does not immunise individuals against inherent limitations of human attention perception
What is the role of expectations and context in perception?
Often presented with ambiguous info
Use contextual info and prior expectations to aid interpretation (Top-down processes/higher processes)
See someone you know but in place that don’t expect to see them - don’t recognise them
-context is wrong (e.g. see colleague in a bakery near your house)
-no expectation that would be there
Schema
What is Schema?
Enduring knowledge structures
used to make sense of a complex world
What are specific medical applications of attention in symptom perception?
Internal (body) and external (environmental) stimuli compete for our attention
When the environment is boring, we pay more attention to the body and notice more symptoms
Distractions commonly used to reduce symptoms (running with music) (nurse ask about weekend when talking blood sample/ tv at dentist)
What are Schemas in symptom perception?
Schemas can drive searches for symptoms and influence interpretation
Pay attention to symptoms we know are part of the diagnosis
e.g. Medical students disease, Mass psychogenic illness (check no organic reasoning)
What is pain perception?
Multi dimensional construct - can be applied to biopsychosocial model
Pain is not directly related to the nature and extent of tissue damage
Psychological and social factors can modify how pain is experienced - attention, expectation, emotional distress, cultural norms
Gate control Theory
What is the Gate control Theory?
Pain perception
Pain is modulated by particular cells in the spinal cord acting as gates blocking some pain signals while sending others to the brain
What is Interposition?
When one object blocks another
Girl behind bars, which are blocking her face, therefore you know she is behind the bars
What is Linear Perspective?
When parallel lines recede into the distance and appear to converge
Adds Depth
Ponso Illusion
What is Texture Gradient?
Units of Texture because smaller or more dense as they recede into the distance
cues about depth
What is Shading?
cues about 3D images
What is the Aerial Perspective?
Objects that are further away appear more fuzzy
What is familiar size?
if we are familiar with the size of an object, and it is smaller than usual in the picture, we know it is far away
What is relative size?
Two objects same size in reality
but one looks smaller than the other then we know it is further away
