Exam #2 Flashcards
Binding problem
Take local info (pieces) to create big picture, there is separation in features (ex: color, shape) of an object and brain must represent which features belong to same object
Solutions to binding problem
Vision exploits regularities in the environment and knowledge from experience, Gestalt= organized whole, complete pattern
What did Kohler believe about the binding problem?
What we actually perceive are entities such as things, figures (unified vs segregated)
What did Gestalt believe about the binding problem?
Organized whole, complete pattern
Similarity
Group based on similar lightness, color, orientation, texture, etc.
Proximity
Group shape in certain areas and spacing to create object/pattern
Common region
Group objects in certain areas
Connection
Connect certain objects together
Symmetry
Create symmetry among objects
Continuation
Ex: line going through a box seems to continue because our brain makes it that way
Closure
2 shapes overlapping each other that are closed seem to form one shape (like a butterfly)
Simplicity
Brain chooses the most simple explanation for missing info
Common fate
Things that move together group together
Figure-ground segregation
Determining what part of environment is the figure so that it “stands out” from background
Properties of figure and background (4)
- Figure is more “thinglike” and more memorable than ground
- Figure is seen in front of ground
- Ground is more uniform and extends behind figure
- Contour separating figure from ground belongs to figure
Factors that determine which area is figure (6)
- Elements located in lower part of displays
- Symmetrical
- Convex
- Small
- Oriented vertically
- Have meaning
Contextual modulation
Stimuli outside of a neuron’s receptive field can affect neural firing
Absolute distance
How far object is from you in the environment
Relative distance
How far an object is to other objects in visual field
3D surface layout
Recovering orientation at a distance
Object shape
Slant, tilt, and curvature
Inverse Problem
Problem of retrieving all visual info about 3D environment using limited into contained in 2D image, same retinal image can correspond to an infinite number of real world objects
Anamorphosis
Distorted projection or perspective (ex: chalk art)
Ames room
Trapezoidal shape of room causes accidental parallel alignment of back wall when viewed through small hole
Large vergence angle=
More convergence, useful only for close distances
Accommodation
Derived by image blur so that the output of high spatial frequency channels is maximized
Occulsion
Condition when a nearer object visually occludes at least a portion of a more distant object(s), closer object seems more near
Size
Retinal image of an object on its size and distance. If you know the size, you can estimate distance (some exceptions)
Geometric perspective
AKA linear perspective: convergence of lines that results in perceived depth in a 2D scene (ex: railroad tracks)
Texture perspective
Density of the surface/object texture increases with distance, providing a depth cue (ex: visual cliff)
Aerial perspective
Objects in distance appear less clear, more blurred and low contrast because of atmosphere and pollution
Shading
Gradient in the reflected light on a 3D object that gives cues about object’s 3D shape, “direction” of depth depends on direction of luminance gradient
Motion parallax
Difference in relative motion of objects located at different distances from the observer (ex: seeing objects while in car)
Projective geometry
Investigates the mathematical relationship between objects in the environment and their optical projections on the retina or on a picture
Stereopsis
3D vision resulting from slight differences in left and right eye images (different perspectives)
How do 3D glasses work?
Red and blue lenses filter the two projected images, allowing only one image to enter each eye
Polarized glasses
Only passes light whose oscillations are oriented in a particular direction
Horopter
Line connecting points that produce corresponding retinal points in the two eyes, objects are at same distance as eye fixation point
Same retinal coordinator caused by….
Points at the same position on each eye that correspond to one another
How are objects projected that are not on the horopter?
Projected to non-corresponding points on two retinas
Crossed disparity
In front of horopter
Uncrossed disparity
Behind the horopter
Zero disparity
Right eye’s image and left eye’s image are at the same location. Point is located on the horopter (i.e. fixation plane)
Disparity
Slight differences in positions of “features” in left and right eye views
Retinal disparity
- Gives info about depth
- Is relative
Chromostereopsis
Blue and red light focused at different positions on retina, creates a disparity between each eye’s view that is perceptually interpreted as a difference in depth
Binocular rivalry
If images in 2 eyes are radically difference, a combined stereo cannot be found
How to enhance stereo vision?
Widen eyes
Basic color
One that cannot further be decomposed upon passing through a prism, can be recombined to create new colors
Metamers
A color that appears to the eye to be identical to another color, but it has different spectral composition
Additive color mixture
Varying proportion of energy from red, green, and blue to create most colors of spectrum (ex: done on TV screens)
Subtractive color mixture
Ex: red pain absorbs and subtracts all wavelengths but the very longest one, remaining wave lengths are reflected from surface to your eyes
Additive vs substractive
- Additive is for mixing lights
- Subtractive is for mixing pigments (paints and materials)
Univariance principle
- Response of a single cone type cannot tell you about the color of the stimulus
- Rod signals do not code info about wavelength of light, only about the intensity of light
Opponent Process Theory of Color
Ex: afterimage- if we view colored stimuli for an extended period of time, we will see an afterimage in a complementary color
Processing for color vision takes place in 2 stages:
- Trichromatic theory
2. Opponent-process theory
Trichromatic theory
- Receptors respond with different patterns to different wavelengths
- Describes what is happening at the very beginning of visual system, in receptors of retina
- Takes minimum of 3 wavelengths to match any wavelength in spectrum
Opponent-process theory
- Neurons integrate inhibitory and excitatory signals from receptors
- Describes events later in visual system
Synesthesia
Neurological condition that causes the brain to process data in the form of several senses at once
Optic flow
Pattern of apparent motion of objects, surfaces, edges in a visual scene caused by the relative motion between an observer and a scene
What is motion? (Democritus)
Nothing more than presence of objects in certain “locations” at certain “times”
Apparent motion
Appearance that objects in the night sky move against the typical direction of motion
What is aliasing in motion?
Illusion, appearance of something that is NOT sue to shortcomings of sampling
Ex: start moving counterclockwise
What is sampling in motion?
Discrete observation or measurement
What does the space/time plot show?
Apparent motion
Corollary discharge
Brain sends copy of motor command to visual system to produce a movement (like a cc in an email)
Where is motion detected?
V1
Where is the “motion area” where detected motions are “interpreted”?
MT
Where does complex motion processing happen?
MST
Where is MT area of brain?
Back of the brain, occipital cortex, critical for normal motion perception
Akinetopsia
Inability to perceive motion
MAE definition
Illusory impression, after prolonged viewing of movement in one direction, that a stationary object is moving in the opposite direction
