Form Perception Flashcards
Qualities of Gestalt Principles
Laws that describe how we orange visual import
Laws are innate or acquired quickly after birth
Figure Ground Principle
Ability to distinguish an object from its background in a visual scene
- Figures tend to have distinct borders that give it form over the background
Proximity Principle
Group elements that are close together in space
- Cluster of daisies
Closure Principle
Fill in gaps in a contour to perceive whole object
- Truck behind pole
Similarity Principle
Group together elements that are physically similar
- rows of vegetation
Continuity Principle
Ability to perceive a simple, continuous form rather than a combination of awkward forms
- x’s as two continuous lines
Common Fate Principle
Group together elements that change in the same way
- objects moving in the same direction (school of fish)
Whole is other than the sum of its parts
the whole has an independent representation in the perception system and cannot be reduced
Processing
enable us to create signal from noise
- Expectation shapes what we see
Bottom-Up Processing
Object recognition is guided by the features that are present in the stimulus
Bottom-Up Recognition
involves comparing every feature to memory
- Link features with similar features in memory
Top-Down Processing
Object recognition is guided by your own beliefs or expectation
- Recognition can be primed
- Needs some input from stimulus
Prime Experiment
the subject is flashed a word to read, is told next word is an animal
- Primed individuals are faster in reading
Bi-Directional activition
Both top-down and bottom up processing guide object recognition
- Recognition can rely on varying degrees of processing
Geon Theory
We have representative geons or geometric forms stored in memory
- Cones, cube, cylinder
Brain Injury
Some deficits can be a person cannot recognize fruit but can recognize different tool
- From Geons
Template Theory
We compare objects to templates in Memory
- If a match is not found, its unfamiliar and stored as a new template
- can be exhausting as you need to store many templates and sort them
Prototype Theory
We compare objects to our ideal prototype
- We store the most ideal examples of an object
- Easily recognize objects never seen before
Perceptual Constancy
Our ability to perceive an object as unchanging even though the visual image produced by the object is constantly changing
Shape Constancy
an object is perceived to have a constant shape despite the shape of its retinal image changing with shifts in point of view or change in object position
Location Constancy
An object is pierced to be stationary despite changing location on our retina due to body movements
Size Constancy
An object is perceived to be the same size despite the size of its retinal image varying with distance
- Objects getting smaller as they walk away
Brightness Constancy
Object is perceived to be the same brightness despite reflecting more or less light onto our retina
Colour Constancy
object is perceived to have a constant colour despite different illumination conditions
Cues Indicate
Depth cues: size of an object relative to distance
Colour cues: influence of a light on a objects colour
Visual Illusions
Muller-Lyer: misapplied size constancy and misinterprets depth
Ames Room: manipulates distance to trick size constancy
Ponzo: manipulates depth cues to trick size constancy
How does the brain process stimuli
In one region before passing it on to the next
- Feature detectors fire in response to select types of stimuli
First step in object recognition
Ganglion cells
Hodgkin & Huxley
Pioneered methods for recording electrical activity in neurons
Primary visual cortex –> feature detectors
Bug detectors
Neurons in the optic nerve of a frog respond only to moving dots
Hubel & Weisel
Some neurons fired only when the line was in a particular place on the retina
- Neuronal activity changed with line orientation
- Sometimes the neurons fired only when the line was moving in a particular direction
- Different types of stimuli (flashes) → not much response
- Crack in slide → neurons fired
What will neurons fire to
Each neuron is specific about what will make it fire the most
- These neurons respond maximally to stimuli of certain shape, size, position and movement → defines the receptive field for that cell
Simple cells
respond maximally to a bar of a certain orientation in a particular region of the retina
Complex Cells
responds maximally to a bar of a certain orientation and direction of movement, regardless of where the bar is located within the receptive field
Complex vs Simple cells
S: Responds most to horizontal bar○bar moved outside/changes orientation →cell will be inhibited and fire below baseline
C: doesn’t care about where in its receptive field the bar is located, and it will even continue to fire if the bar is moving within the receptive field
Hypercomplex Cells
respond maximally to a bar of a particular orientation and direction of movement, ending at specific points within the receptive field
